Soil Based Research: Agriculture, Horticulture & Forestry

Wollastonite is a versatile and unique white mineral with proven benefits across a wide range of plant types and environments. The combination of a readily available supply of calcium and silicon can account for the positive effects of wollastonite in a wide range of soil based research studies.

Many of these studies are summarized under the following linked topic areas:

1. General Overview

2. Nutrient Management

3. Horticultural Crops

4. Field Crops & Grasses

5. Forestry

6. Disease Suppression

7. Carbon Sequestration

8. Environmental Stress Tolerance

9. Silicon Cycling

 

1. General Information

1.1 An Introduction to Silicon Nutrition of Soils and Crops

Silicon (Si) has recently been recognized as a quasi-essential element in plant nutrition. Some plant species, such as diatoms and equisetum, cannot grow without silicon. Other plants benefit from silicon nutrition to various degrees depending on the environmental conditions. Rice, wheat, cucurbits, and sugarcane are examples of crops that often benefit from enhanced levels of silicon nutrition. In crop production the benefits from silicon may include increased yield, disease and insect resistance, and tolerance to stresses such as cold, drought, and toxic metals. In addition to plants, the value of silicon is gaining attention in animal nutrition where silicon has been shown to play a role in the health of bone, joints, skin, hair, and other connective tissues.

See related topics and documents: An Introduction to Silicon Nutrition of Soils and Crops.pdf

1.2 Silicon and Soil Fertility

Wollastonite is naturally occurring mined calcium silicate. Mined minerals are usually permitted for use in organic farming. Finely ground wollastonite is a good source of plant available silicon. However, organic farmers should check with their certifier to be sure that a particular source of silicon fertilizer it is permitted for use in organic farming.

See related topics and documents: Silicon and Soil Fertility.pdf

1.3 Silicon – A beneficial substance

Silicon (Si) has been officially designated as a plant “beneficial substance” by the Association of American Plant Food Control Officials {AAPFCO) and plant-available Si may now be listed on fertilizer labels.

Silicon is a major component of sand, silt and clay minerals. Because of this abundance, it typically has not been considered as a limiting factor in soil fertility. However numerous field studies have shown that supplying crops with adequate plant-available Si can suppress plant disease, reduce insect attack, improve environmental stress tolerance, and increase crop productivity.

See related topics and documents: Silicon: A Beneficial Substance.pdf

 

1.4  A note on: Dolomitic Lime CaMg(CO3)2 vs Wollastonite

Calcium Magnesium Carbonate: DOLOMITE is a double carbonate of calcium and magnesium, CaCO3, MgCO3. The mineral was first identified by Count Dolomien in 1791 and named after its discoverer. It is of sedimentary origin and is supposed to have been formed due to chemical action of sea-water containing a high percentage of magnesia, on limestone. Theoretically, dolomite contains: CaCO3 54.35% MgCO3 45.65%. In other words, it contains: CaO 30.4%, MgO 21.7%, CO2 47.9%
The principal advantages of Wollastonite & Diopside over Calcium Magnesium Carbonate in pH modification of soils and Ca/Mg supplementation of feeds and fertilizers are:
a) the reaction is slower and less likely to overshoot;
b) CO2 is not generated in the process.
Each 1 tonne of Ca produced from carbonate sources releases ~1.5 tonnes of CO2

 

1.5 Fight Global Warming By Boosting Calcium Silicates In Soil – Theory

Plants, crops and trees naturally absorb atmospheric carbon dioxide (CO2) during photosynthesis and then pump surplus carbon through their roots into the earth around them. In most soils, this carbon can escape back to the atmosphere or enters groundwater.

Knowing this, a team from Newcastle University aims to design soils that can remove carbon from the atmosphere, permanently and cost-effectively using soils containing calcium-bearing silicates.

Calcium silicates are minerals that occur naturally in many different rocks and also in artificial materials such as concrete. (Wollastonite is a pure calcium silicate)

The team believe the carbon that oozes out of a plant’s roots may react with the calcium to form the harmless mineral calcium carbonate(1). The carbon then stays securely locked in the calcium carbonate, which simply remains in the soil, close to the plant’s roots, in the form of a coating on pebbles or as grains.

See related topics and documents: Fight Global Warming By Boosting Calcium Silicates In Soil – Theory.pdf

1.5.1 Carbon-sequestering fertilizers for augmented carbon storage capacity of agricultural soils – Active Project

The weathering of basic silicate minerals and subsequent precipitation of stable Ca- and Mg-carbonates is the main geological process removing CO₂ and controlling its concentration in the atmosphere. Enhanced weathering can sequester CO₂ at an accelerated pace, by exposing milled minerals to CO₂ in the air and within soils. Sequestration capacity is proportional to mineral application rate and land area coverage. This project will formulate fertilizer blends that include basic minerals as carbon-sinks, test these fertilizers in laboratory and field trials, and validate enhanced weathering as a means to increase the fixed carbon content of agricultural soils. The end result of this project will be the delivery of a new environmental protection tool for the agricultural sector in Ontario, the formation of new partnerships with regional industries and rural communities, and the advancement of the state-of-knowledge on climate change mitigation.

First publication from this project: Co-Benefits of Wollastonite Weathering in Agriculture.pdf

Full project summary: LCIF-Summary-Emily-Chiang.pdf

Canadian Wollastonite is a proud supporter of this research project with Dr. Emily Chiang at the School of Environment, University of Guelph, Ontario.

 

1.6 The role of silicon in higher plants under salinity and drought stress

Although deemed a “non-essential” mineral nutrient, silicon (Si) is clearly beneficial to plant growth and development, particularly under stress conditions, including salinity and drought. Here, we review recent research on the physiological, biochemical, and molecular mechanisms underlying Si-induced alleviation of osmotic and ionic stresses associated with salinity and drought. We distinguish between changes observed in the apoplast (i.e., suberization, lignification, and silicification of the extracellular matrix; transpirational bypass flow of solutes and water), and those of the symplast (i.e., transmembrane transport of solutes and water; gene expression; oxidative stress; metabolism), and discuss these features in the context of Si biogeochemistry and bioavailability in agricultural soils, evaluating the prospect of using Si fertilization to increase crop yield and stress tolerance under salinity and drought conditions.

See related topics and documents: The Role of Silicon in Higher Plants under Salinity and Drought Stress.pdf

1.7 Towards establishing broad-spectrum disease resistance in plants: Silicon leads the way

See related topics and documents: Towards establishing broad-spectrum disease resistance in plants- silicon leads the way.pdf

 

2. Nutrient Management

2.1 Effect of Calcium Silicate on the Phosphorus Sorption Characteristics of Andisols Lembang West Java

The effect of calcium silicate CaSi03 on the phosphorus (P) sorption characteristics was studied in Andisols Lembang. The amount of 0, 2.5 and 5% CaSi03 (calcium silicate) or 0, 7.5 and 15 g calcium silicate per pot was added to the 300 g (oven-dry weight) soil and incubated for one month. A completely randomized design in double replication was set up. After one-month incubation, P sorption and P sorption kinetic experiments were conducted The results of P sorption experiment showed that P sorption data were satisfactorily described by the Langmuir equation, which was used to determine P sorption maxima, bonding energies and P sorbed at 0.2 mg P C1 (standard P requirement). The application of calcium silicate did not affect significantly P sorption maxima but decreased significantly the P bonding energies. Calcium silicate also decreased significantly the standard P requirements. As for P sorption kinetic experiment, the results showed that application of 5% calcium silicate decreased significantly the rate constant of P sorption and P sorbed maximum at given amount of added P. The results suggested that the application of calcium silicate to the Andisols made added P was more available for plant.

See related topics and documents: The Effect of Calcium Silicate on The Phosphorus Sorption Characteristics of Andisols Lembang West Java

2.2 Phosphorus removal by wollastonite: A constructed wetland substrate

Abstract: Wollastonite, a calcium metasilicate mineral mined in upstate New York, is an ideal substrate for constructed wetland ecosystems for removing soluble phosphorus from secondary wastewater. Design parameters, required for designing a full-scale constructed wetland, were measured in vertical upflow columns with hydraulic residence times varying from 15 to 180 h. Secondary wastewater was pumped vertically upward through eleven soil columns, 1.5 m in length and 15 cm in diameter and influent and effluent concentrations of soluble phosphorus were monitored for up to 411 days. Greater than 80% removal (up to 96%) was observed in nine out of 11 columns and effluent concentrations of soluble phosphorus ranged from 0.14 to 0.50 mg:l (averaging 0.28 mg:l) when the residence time was \40 h. Columns with a decreased residence time averaged 39% removal. A direct relationship between residence time and soluble phosphorus removal was established.

See related topics and documents: Phosphorus removal by wollastonite.pdf

2.3 Surface application of limestone and calcium-magnesium silicate in a tropical no-tillage system

Read our full blog and summary about this study here

Abstract:

Although lime is currently the most commonly applied material for soil acidity correction in Brazil, calcium-magnesium silicate application may efficiently replace this source due to its higher solubility and silicon supply, which is beneficial for plant development. This study aimed to evaluate the efficiency of surface liming and silicate application on soil chemical attributes as well as soybean and maize nutrition, yield components, and grain yield. The experiment was conducted in a Rhodic Hapludox in Botucatu-SP, Brazil. The randomized complete block design contained 16 replications. Treatments consisted of two materials for soil acidity correction (dolomitic lime, calcium/magnesium silicate), applied on October 2006 to raise base saturation up to 70%, and a control, with no acidity correction. Soybean and maize were sown in 2006/2007 and 2007/2008, respectively. After 18 months Ca-Mg silicate corrected soil acidity up to 0.60 m, and increased exchangeable base levels up to 0.40 m. Silicate increased silicon concentrations in plant tissues in both crops as well as phosphorus in soybean. The application of both sources increased calcium and magnesium concentrations as well as yield components and yield grains of soybean and maize. Soil acidity correction improved the efficiency of fertilizers applied for grain production.

See related topics and documents: Wollastonite Lime Comparison in Brazil Notill.pdf

2.4 The relationship between silicon and soil physical and chemical properties

2.5 Neoformed aluminosilicate and phytogenic silica are competitive sinks in the silicon soil–plant cycle

In soils, mineral weathering and phytolith dissolution release aqueous monosilicic acid that can be taken up by plant, adsorbed on mineral surfaces, entrapped in neoformed clay minerals, or exported to watersheds. The balance between biotic and abiotic processes determines the fluxes of bioavailable silicon (Si), impacting plant growth and health, and diatoms biomass, hence the oceanic capacity to fix carbon dioxide. Here we quantified this balance in an experimental system using rice and an albic soil material (quartz grains) containing now weatherable silicate minerals. Materials representing a soil weathering gradient were prepared by adding variable amounts of silicate minerals within fresh powdered tephrite (< 83 μm) as a source of weatherable minerals whereas phytogenic Si was supplied within phytolith-rich biochar. We quantified the distribution of Siin leachate, soil and plant reservoirs. Weatherable minerals rapidly released Si that flowed into two main sinks: allophanic substances neoformed in soil from released Si and aluminum (Al), and phytoliths formed by precipitation of absorbed silica in plant tissues. The leaching of Si was negligible. Allophane rapidly formed at a maximum rate of 0.85 g allophane kg−1soil day−1. Of the Si stock of weatherable minerals, 7–14% contributed to allophanic Si and less than 1% to phytogenic Si. The contribution of supplied phytoliths to plant Si accumulation markedly increased from 26 to 80% with the decrease in weatherable mineral reserve from 405 to 5cmolckg−1. Weatherable minerals primarily controlled bioavailable Si while phytoliths increasingly contributed o Si plant uptake with increasing mineral depletion. Returning phytoliths to soil thus boosts the biological recycling of Si in proportion to the increase in soil weathering stage.

Read our blog on this study here

Read the full study: Neoformed aluminosilicate and phytogenic silica are competitive sinks in the silicon soil-plant cycle.pdf

2.7 Improvement of the physiological response of barley plants to both Zinc deficiency and toxicity by the application of calcium silicate

An adequate availability of Zinc (Zn) is crucial for plant growth and development given the essentiality of this element. Thus, both Zn deficiency and Zn toxicity can limit crop yields. In plants, the responses to Zn imbalances involve important physiological aspects such as reactive oxygen species (ROS) accumulation, phytohormone balance, tricarboxylic acid cycle (TCA) metabolism, and organic acids (OAs) accumulation. However, a way to improve tolerance to stresses such as those produced by nutritional imbalances is the application of beneficial elements such as silicon (Si). In this study, we grew barley plants in hydroponics under Zn deficiency and toxicity conditions, applying Si in the form of CaSiO3 in order to assess its effectiveness against Zn imbalances. Parameters related to plant growth, oxidative stress, TCA enzyme activities, phytohormones and OAs accumulation were analyzed. Both Zn deficiency and toxicity reduced leaf biomass, increased ROS accumulation, and affected phytohormone and OAs concentrations and TCA enzyme activities. CaSiO3 treatment was effective in counter-acting these effects enhancing Zn accumulation under Zn deficient conditions and limiting its accumulation under toxic conditions. In addition, this treatment decreased ROS levels, and improved ascorbate/glutathione and phytohormonal responses, citrate synthase activity, and malate/oxalate ratio. Therefore, this study enhanced the notion of the efficacy of CaSiO3 in improving tolerance to Zn imbalances

Full study: Improvement of the physiological response of barley plants to both Zinc deficiency and toxicity by the application of calcium silicate.pdf

 Click here to view our blog involving this study

3. Horticultural Crops

3.1 Pumpkin Production Practices that Reduce Cost

Pumpkin growers looking for new cultural practices to improve production and fruit quality while reducing input cost may benefit from findings of research conducted at the Rutgers University, New Jersey Agricultural Experiment Station.

One of our experiments compared the influence of different types of liming materials to neutralize soil acidity and improve pumpkin plant health. Regular agricultural limestone, chemically referred to as calcium carbonate, was compared with calcium silicate in a field with an initial soil pH of 5.9. Calcium silicate is an alternative liming material that supplies the nutrient silicon in a plant available form. Silicon is now recognized as a quasi-essential nutrient with beneficial effects on disease suppression and stress tolerance on several crops.

Wollastonite is a naturally occurring mined source of calcium silicate that may be an acceptable Si fertilizer

See related topics and documents: Pumpkin Production Practices that Reduce Cost.pdf

3.2 Calcium Silicate and organic mineral fertilizer applications reduce Phytophagy on Eggplants

Thrips palmi Karny (Thysanoptera: Thripidae) is a phytophagous insect associated with the reduction of eggplant productivity. The aim of this study was to evaluate the effect of calcium silicate and/or an organic mineral fertilizer, together or separately, in increasing the resistance of eggplants to T. palmi. The treatments were calcium silicate, organic mineral fertilizer, calcium silicate associated with this fertilizer and the control. Mortality and number of lesions caused by nymphs of this insect on eggplant leaves were evaluated after 3, 6, 9 and 12 leaf applications of these products. The calcium silicate and the organic mineral fertilizer reduced both the population of T. palmi and the damage caused by its nymphs, suggesting a possible increase in eggplant resistance to this pest as a result of the treatments.

See related topics and documents: Calcium Silicate and organic mineral fertilizer applications reduce Phytophagy on Eggplants.pdf

3.3 Calcium silicate and organic mineral fertilizer increase the resistance of tomato plants to Frankliniella schultzei

Frankliniella schultzei Trybon (Thysanoptera: Thripidae) is an important pest of tomato plants. The need for more healthful foods is stimulating the development of techniques to increase plant resistance to phytophagous insects. The objective of this research was to evaluate the effect of calcium silicate and an organic mineral fertilizer, alone or in combination, on the resistance of tomato plants to F. schultzei. The treatments consisted of: control (T1), calcium silicate (T2), organic mineral fertilizer (T3), and calcium silicate with organic mineral fertilizer (T4). The mortality of nymphs of this thrips and the number of lesions on tomato leaves were evaluated after three, six, nine and 12 applications of these products. The number of F. schultzei individuals and of lesions on tomato leaves was lower in treatments T2 and T4 than in T1 and T3, showing a possible increase in tomato resistance to this pest. The increase in the number of applications of calcium silicate and the organic mineral fertilizer increased the mortality of nymphs and reduced the damage by this insect on tomato leaves, mainly after nine applications.

See related topics and documents: Calcium silicate and organic mineral fertilizer increase.pdf

3.4 Does Silicon Have a Role in Ornamental Crop Production?

Silicon (Si) is not considered an essential plant nutrient because most plant species can complete their life cycle without it. Still, some plants can accumulate Si at concentrations greater than nitrogen and potassium, and all flower species evaluated so far have concentrations of Si in tissue greater than the micronutrients boron, copper, and zinc.

A clear benefit of Si for some ornamental crops has been reported. These include decreased bract edge burn in poinsettia; decreased powdery mildew in zinnia, sunflower, and phlox; enhanced flower size of gerbera; resistance to metal toxicity in zinnia; decreased population growth of aphids on zinnia; improved salt-tolerance in New Guinea impatiens; and improved shelf-life of poinsettia. As a result of these positive responses, interest in using Si in ornamental crop production has increased.

See related topics and documents: Silicon_OFA_Bulletin.pdf

3.5 Silicon enhances disease suppression

The results of several experiments indicate that silicon affects plant growth and crop quality, stimulates photosynthesis, reduces transpiration rate and enhances plant resistance to stresses, such as water, chemical, nutrient imbalances, metal toxicities, diseases and pests.

Our goal during the past five years was to determine if silicon might provide benefits to greenhouse-grown floral crops.

See related topics and documents: Silicone enhances disease suppression.pdf

3.6 Comparison of different calcium sources on avocado production

Liming materials and gypsum were shown to increase avocado fruit production when applied annually in moderate amounts, but was detrimental when excessive applications were made. Extractable Al was shown to be a better indicator of lime requirement than soil pH.

Positive residual effects were obtained with all treatments to a certain extent. Calcium concentrations in both leaves and fruit were only slightly affected by these treatments, and did not correspond with the effects obtained on yield.

See related topics and documents: Comparison of different calcium sources on avocado production.pdf

3.7 Response of Silicon and Micro Nutrients on Fruit Character and Nutrient Content in Leaf of Sapota

Experiment was conducted to know the response of nutrients on fruit character and its influence on enhancing yield and quality and also on accumulation of nutrients in leaf. Potassium silicate, calcium silicate was taken as silicon source and solubor as boron and kiecite-G were used as micronutrient source. Fruit characters like fruit weight (99.96 g), fruit length (5.55 g), fruit diameter (5.85 g), volume of fruit (102.38 g) and maximum shelf life (10.90 days) was recorded with treatment supplemented with foliar application of potassium silicate at 8 ml per litre. Highest yield per tree (124.81 kg) and hectare (12.48 t) were recorded in treatment supplemented with foliar application of potassium silicate at 8 ml per litre where as highest B:C ratio (2.36) was recorded in treatment which is supplied calcium silicate as soil application. The highest nutrients like nitrogen (1.583 %), phosphorous (0.175 %), potassium (1.20 %) and silicon content (1.20 %) in leaf were recorded with potassium silicate spray (8 ml per litre).

See related topics and documents: Response of silicon and micro nutrients on fruit character and nutrient content in leaf of sapota.pdf

 

Silicon has generally not been considered essential for plant growth, although it is well recognized that many plants, particularly Poaceae, have substantial plant tissue concentrations of this element. Recently, however, the International Plant Nutrition Institute [IPNI] (2015), Georgia, USA has listed it as a “beneficial substance”. This reflects that numerous studies have now established that silicon may alleviate both biotic and abiotic stress. This paper explores the existing knowledge and recent advances in elucidating the role of silicon in plant defense against biotic stress, particularly against arthropod pests in agriculture and attraction of beneficial insects. Silicon confers resistance to herbivores via two described mechanisms: physical and biochemical/molecular. Until recently, studies have mainly centered on two trophic levels; the herbivore and plant. However, several studies now describe tri-trophic effects involving silicon that operate by attracting predators or parasitoids to plants under herbivore attack. Indeed, it has been demonstrated that silicon-treated, arthropod- attacked plants display increased attractiveness to natural enemies, an effect that was reflected in elevated biological control in the field. The reported relationships between soluble silicon and the jasmonic acid (JA) defense pathway, and JA and herbivore- induced plant volatiles (HIPVs) suggest that soluble silicon may enhance the production of HIPVs. Further, it is feasible that silicon uptake may affect protein expression (or modify proteins structurally) so that they can produce additional, or modify, the HIPV profile of plants. Ultimately, understanding silicon under plant ecological, physiological, biochemical, and molecular contexts will assist in fully elucidating the mechanisms behind silicon and plant response to biotic stress at both the bi- and tri-trophic levels.

See related topics and documents: Silicon: Potential to Promote Direct and Indirect Effects on Plant Defense Against Arthropod Pests in Agriculture.pdf

 

3.9 Silicon enhances natural enemy attraction and biological control through induced plant defences

See related topics and documents: Silicon enhances natural enemy attraction and biological control through induced plant defences.pdf

3.10 Building Soil Fertility Using Soil Amendments

From Abstract:

Of the various non-carbonate amendments, CaMgSilicate (Agrowsil), Calcium Silicate (Wollastonite), and wood ash significantly increased soil pH similar to calcite and dolomite. CaMgSilicate and calcium silicate amendments increased Soil test extractable Si levels by tenfold over unamended soil, calcite and dolomite. Si concentration in rye tissue was higher in CaMgSilicate plots (3.7 g/kg) than limestone plots (2.7 g/kg). Silicon level in pumpkin tissue was higher in calcium silicate (6575 mg kg-1) than CaMgSilicate (4000 mg kg-1). Calcium silicate delayed the onset of powdery mildew disease by 20 fold more than all amendments. The study found that calcium silicate and wood ash could be a useful alternative for limestone and calcium silicate may help protect pumpkin crops against disease.

Read the full thesis here: Building soil fertility using soil amendments.pdf

4. Field Crops & Grasses

4.1 Silicon: An essential Plant Nutrient?

Groundbreaking Research Demonstrates Benefits on a Variety of Crops

According to Heckman, field trials using calcium silicate indicate that enhanced levels of silicon uptake can provide additional crop benefits beyond its use as a liming material. While powdery mildew disease in pumpkin fruit and wheat grain was suppressed, in some years Heckman found that yields were also increased on the plots in which calcium silicate was added.

He also found that:

Corn plants grown on soil previously amended with calcium silicate had less stem damage from European corn borer.
Yields of forage grains improved equally whether limed with calcium carbonate or calcium silicate.
While cabbage yields were improved overall from liming, the addition of calcium silicate did increase the yields of marketable heads more than calcium carbonate.
The benefits of residual calcium silicate applications were still evident in crops produced three to four years after the last application.

See related topics and documents: Silicon – An essential plant nutrient.pdf

4.2 Calcium Silicate Suppressed Powdery Mildew and Increases Yield of Field Grown Wheat

Abstract: During three consecutive years of field trials conducted in northwestern New Jersey on a Quakertown silt loam soil (fine–loamy, mixed, active, mesic Typic Hapludult), a calcium silicate, steel slag by-product (CSS), was added as an effective liming agent to long winter wheat (Triticum aestivum L.) and evaluated for its suppressive effects on powdery mildew disease (Erysiphe graminis DC. f. sp. tritici Em. Marchal Blumeria graminis (DC.) E.O. Speer = E. graminis DC. Oidium monilioides (Nees) Link [anamorph]). Limestone was used as the control in a completely random design, consistent for treatment during all trial years. Plots were split for one fungicide, propiconazole (1-[[2(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]1-H-1,2,4-triazole), application per year. The field was allowed to become naturally inoculated. In 2006 disease symptoms did not appear until late in the season. Although no significant grain yield response was exhibited in 2006, powdery mildew lesions were reduced by 29% on the flag leaves of wheat plants in the CSS treated plots. In 2007, powdery mildew was not diagnosed, but non-pathogenic Alternaria spp. leaf blotch was observed late season. Leaf blotch lesions were reduced 25% on flag leaves in the CSS-treated plots. During 2008, powdery mildew lesions on flag leaves were 44% less and yields were 10% greater in plots treated with CSS. Our results suggest that the use of CSS as an effective neutralizer of soil acidity may have the added benefit of suppressing powdery mildew in field grown winter wheat.

See Soil Science Society of America – doi:10.2136/sssaj2010.0134: https://www.soils.org/publications/sssaj/abstracts/74/5/1652

4.3 Optimization of Source and Rate of Soil Applied Silicon for Improving the Growth of Wheat

Silicon (Si) is known to be a beneficial element that involved in improving the growth of many crops. It was hypothesized that effective source and optimized rate of soil applied Si could promote the growth of the wheat under normal condition. Thus, this study aimed to assess the effective source and best level of soil applied Si on the growth of the wheat seedling. Experiment was comprised of three silicon sources (sodium silicate, calcium silicate and silicic acid) and four concentrations (0, 50, 100 and 150 mg kg-1). Wheat plants were harvested 40 days after sowing and evaluation was made on the basis of different morphological characteristics of the plants. Results revealed that soil applied Si improved the growth of wheat plant when compared to control. Significantly the higher shoot and root length, their fresh and dry weights, shoot: root ratio, total plant biomass was obtained when 100 and 150 mg kg-1 Si applied from Ca-silicate. However, these two levels were at par with each other in many parameters observed. The current results also enabled us to select the most effective (100 mg kg-1) out of four levels of Si from Ca-silicate.

See related topics and documents:Optimization of Source and Rate of Soil Applied Silicon for Improving the Growth of Wheat.pd

4.4 Efficiency of Calcium Silicate and Carbonate in Soybean Disease Control

Silicon (Si) affects the susceptibility of plants to fungal attack. In plants with low Si accumulation, disease-control mechanisms involve the accumulation of phenolic compoundsand Si. This study compared the effects of calcium silicate and carbonate doses on the control of soybean (Glycine max) diseases. A sandy soil was collected from Santa Vit´oria, Minas Gerais state, Brazil, of which 200 kg was placed in plastic drums in a protected, uncovered area. Calcium carbonate or silicate was applied superficially in amounts equivalent to 0, 1500, 3000, 6000, or 12,000 kg ha−1, and soybean was cultivated for 120 d. Leaf Si concentration and incidence of Cercospora sojina (Frog’s eye spot), Peronospora manshurica (downy mildew), and Phakopsora pachyrhizi (Asian rust) were evaluated. Calcium carbonate did not reduce disease incidence; however, calcium silicate was effective in the reduction of downy mildewat 47 and 66 d after soybean seeding, and of frog’s eye spot incidence at all dates evaluated. Asian rust was observed only at 79 d after seeding and calcium silicate was not effective in its reduction.

Conclusions: A pre-seeding soil application of silicate increased leaf-tissue silicate concentration. This greater leaf concentration was effective on reducing downy mildew incidence at 47 or 66 d after seeding, and frog’s eye spot at all evaluations; however, no control of Asian rust was observed. In contrast, calcium carbonate did not reduce frog’s eye spot, downy mildew, or Asian rust incidence.

See related topics and documents: Efficiency of Calcium Silicate and Carbonate in Soybean Disease Control.pdf

4.5 Calcium Chloride and Calcium Silicate decrease white mold intensity on common beans

Both incidence and severity of white mold were significantly reduced by one application of CaCb and CaSiOs at early bloom, but the level of control was not sufficient to increase yield. Two applications of fluazinam decreased white mold incidence and severity (P < 0.01) and increased yield (P < 0.05) (Table 1). Reduction of disease with two applications of CaCl2 and CaSiOa was only significant for DSI (P < 0.05). Compared to untreated control, fluazinam reduced disease incidence by 52 %, severity by 73 %, and increased yield by 45 % (Table 1). Venette (1998) found that foliar applied calcium enhanced both disease control and yield. He suggested that calcium may be a nutritional supplement that increases plant resistance to white mold. Nutritional effect is particularly noticeable in the case of calcium compounds with high water solubility, like CaCb. As CaSiOs has very low water solubility, possible effects of its foliar application may also be explained by the establishment of a physical barrier on the host tissue. Moreover, many modifications may occur in the plant surface after calcium application, including increase of pH and changes in the populations of microorganisms.

See related topics and documents: Calcium Chloride and Calcium Silicate decrease white mold intensity on common beans.pdf

4.6 Silicon and the Development of Gray Leaf Spot of Perennial Ryegrass Turf

Studies were conducted at The Pennsylvania State University in controlled-environment chambers and microplots where perennial ryegrass pots were buried among perennial ryegrass turf to determine the effects of silicon amendments on gray leaf spot development. Tissue silicon content increased consistently with increasing amount of silicon in the soils, while disease incidence decreased consistently with increasing tissue silicon content in all four soil and source combinations under both experimental conditions. SUMMARY: Silicon amendments have been proven effective in controlling fungal diseases of various crops. However, effects of silicon amendments on gray leaf spot (Magnaporthe ryzae) of perennial ryegrass are not known. Studies were conducted at The Pennsylvania State University in controlled-environment chambers and microplots where perennial ryegrass pots were buried among perennial ryegrass turf to determine the effects of silicon amendments on gray leaf spot development. Plants were grown in two soil types: peat:sand mix (soil Si = 5.2 mg/liter) and Hagerstown silt loam (soil Si = 70 mg/liter). Both soil types were amended with two sources of silicon—wollastonite and calcium silicate slag—at 0, 0.5, 1, 2, 5, and 10 metric tons/ha and 0, 0.6, 1.2, 2.4, 6, and 12 metric tons/ha, respectively. Nine-week-old perennial ryegrass was inoculated with M. oryzae. Gray leaf spot incidence and severity were assessed two weeks after inoculation. Gray leaf spot incidence and severity of perennial ryegrass significantly decreased by different rates of wollastonite and calcium silicate slag applied to both soils under both experimental conditions. Tissue silicon content increased consistently with increasing amount of silicon in the soils, while disease incidence decreased consistently with increasing tissue silicon content in all four soil and source combinations under both experimental conditions. These findings suggest that silicon amendments may be utilized in integrated gray leaf spot management programs on perennial ryegrass.

See related topics and documents:Turfgrass and Environmental Research Online.pdf

4.7 Accumulation of Silicon by Bermudagrass to Enhance Disease Suppression of Leaf Spot and Melting Out

Soluble silicon (Si) has enhanced the growth and development of several plant species including rice, sugarcane, and most other cereals crops. Researchers at the University of Florida conducted experiments to determine if bermudagrass can accumulate silicon and if silicon could enhance host plant resistance to Bipolaris cynodontis, the causal organism of leaf spotting and melting out of bermudagrass. They found: There was a significant linear increase in silicon that accumulated in the leaves of bermudagrass as the rate of calcium silicate amended to the soil increased. Silicon also was very effective in suppressing leaf spot development on bermudagrass caused by B. cynodontis. Final % leaf spot severity was reduced by 38.9% compared to untreated controls. These results suggest that when soils low or limiting in plant available silicon are amended with a soluble source of silicon, the resistance of bermudagrass against leaf spotting caused by B. cynodontis can be enhanced. This also suggests that fungicides might be better managed if used in combination with silicon for controlling diseases in turf.

See related topics and documents: Accumulation of Silicon by Bermudagrass to Enhance Disease Suppression of Leaf Spot and Melting out.pdf

4.8 Carbonate-silicate ratio for soil correction and influence on nutrition, biomass production and quality of palisade grass

Silicates can be used as soil correctives, with the advantage of being a source of silicon, a beneficial element to the grasses. However, high concentrations of silicon in the plant would affect the digestibility of the forage. To evaluate the influence of the substitution of the calcium carbonate by calcium silicate on the nutrition, biomass production and the feed quality of the palisade grass [Urochloa brizantha (C. Hochstetter ex A. Rich.) R. Webster], three greenhouse experiments were conducted in completely randomized designs with four replications. Experimental units (pots) contained a clayey dystrophic Rhodic Haplustox, a sandy clay loam dystrophic Typic Haplustox and a sandy loam dystrophic Typic Haplustox. Each soil received substitution proportions (0, 25, 50, 75 and 100 %) of the carbonate by calcium silicate. The increase in the proportion of calcium silicate elevated the concentrations and accumulations of Si, Ca, Mg, and B, reduced Zn and did not alter P in the shoot of plants. The effects of the treatments on the other nutrients were influenced by the soil type. Inclusion of calcium silicate also increased the relative nutritional value and the digestibility and ingestion of the forage, while the concentration and accumulation of crude protein and the neutral detergent and acid detergent fibers decreased. Biomass production and feed quality of the palisade grass were generally higher with the 50 % calcium silicate treatment.

See related topics and documents: Carbonate-silicate ratio for soil correction and influence on nutrition biomass production and quality.pdf

4.9 Silicate and Phosphate combinations for Marandu Palisadegrase growing on an oxisol

Wollastonite was used as the source of silicate and the sources of phosphorus were Ca(H2PO4)2, KH2PO4 and NaH2PO4. Marandu palisadegrass was grown during the summer and two harvests were made during the growing season. Significant interaction between phosphorus and silicate rates was found for the number of tillers and expanded green leaves, total leaf area, dry mass production of leaf laminae and culms with sheaths, and dry mass production of plant tops. Maximum responses of the analyzed variables were reached in the combination of the intermediate rates of phosphorus (170 and 250 mg dm-3) with high rates of silicon (375 and 450 mg dm-3).

See related topics and documents: Silicate and Phosphate combinations for Marandu Palisadegrase Growing on an Oxisol.pdf

4.10 Role of Silicon in Suppressing Rice Diseases

The beneficial effects of Si to plants under biotic and/or abiotic stresses have been reported to occur in a wide variety of crops such as rice, oat, barley, wheat, cucumber, and sugarcane. Leaves, stems, and culms of plants, especially rice grown in the presence of Si, show an erect growth, thereby the distribution of light within the canopy is greatly improved (Fig. 3) (11,12,42,57). Silicon increases rice resistance to lodging and drought and dry matter accumulation in cucumber and rice (1,12,40). Silicon can positively affect the activity of some enzymes involved in the photosynthesis in rice and turfgrass (57,58) as well as reduce the senescence of rice leaves (33). Silicon can lower the electrolyte leakage from rice leaves and, therefore, promote greater hotosynthetic activity in plants grown under water deficit or heat stress (2). Silicon increases the oxidation power of rice roots, decreases injury caused by climate stress such as typhoons and cool summer damage in rice, alleviates freezing damage in sugarcane, favors supercooling of palm leaves, and increases tolerance to freezing stress in some plants (21,57). Silicon reduces the availability of toxic elements such as manganese, iron and aluminium to roots of plants such as rice and sugarcane and increases rice and barley resistance to salt stress (22,41,57).

See related topics and documents: The Role of Silicon in Suppressing Rice Diseases.pdf

4.11 Effect of Calcium Silicate on Yield and Nitrogen use efficiency

Field experiment was conducted to investigate the effect of calcium silicate application on the growth, yield and nitrogen use efficiency (NUE) of wetland rice at eastern dry zone soils of Karnataka, using Cv. BI-34, a medium duration rice genotype. Results revealed that the significantly highest grain and straw yield was noticed with 100 kg N ha-1 (RDF) along with the application of calcium silicate @ 2t ha-1 over all other treatments. The increase in growth and yield attributes might be due to the supplement of calcium silicate as silicon source. Application of silicon sources along with RDF and LCC based nitrogen application significantly increased the test weight over control.

See related topics and documents: The effect of Calcium Silicate on yield and nitrogen use efficiency.pdf

4.12 Growth of rice plants in an Acrustox fertilized with silicon and manganese

The objective of this research was to study the biomass production, plant architecture and Si and Mn uptake in rice plants cultivated in a Acrustox fertilized with silicon and manganese. The experiment was carried out in a greenhouse using a 2×5 factorial (0 and 1000mg dm-3 Si x 0, 4, 12, 16 and 20mg dm-3 Mn) with four replications, in a randomised block design. The application of Si to the soil resulted in a smaller leaf insertion angle, a greater Si content in the leaves an d roots and biomass production. Moreover, Si caused the decrease content of Mn in leaves and its increase in roots. With the rising dose of Mn, there was an increase in the content of this element in soil, roots and leaves, regardless of the Si application and reduction in biomass production of rice in the larger doses only when the Si was not added to the soil. The availability of Mn increases in acid soils and may cause toxicity problems since high plant Mn concentrations may severely reduce plant production (EL-JAOUAL & COX, 1998). Lime application, which reduces Mn availability by increasing the pH of the soil, may avoid the Mn toxicity (OLIVEIRA JÚNIOR. et al., 2000). It has been reported that Si performs a very important role in plant tolerance to toxicity caused by Mn, a fact observed in various species such as rice, bean, cowpea and cucumbers. It diminishes the transport of Mn from the roots to the shoots with strong connection of Mn to the cell wall; reducing its concentration in the symplast and the lipid peroxidation of the membrane (LIANG et al., 2007). These reported studies are related to experiments with plants growing in nutrient solution.

See related topics and documents: Growth of rice plants in an Acrustox fertilized with silicon and manganese.pdf

4.13 Silicon Nutrition and Sugarcane Production

Silicon (Si) is one of the most abundant elements found in the earth’s crust, but is mostly inert and only slightly soluble. Agriculture activity tends to remove large quantities of Si from soil. Sugarcane is known to absorb more Si than any other mineral nutrient, accumulating approximately 380 kg ha-1 of Si, in a 12-month old crop. Sugarcane (plant growth and development) responses to silicon fertilization have been documented in some areas of the world, and applications on commercial fields are routine in certain areas. The reason for this plant response or yield increase is not fully understood, but several mechanisms have been proposed. Some studies indicate that sugarcane yield responses to silicon may be associated with induced resistance to biotic and abiotic stresses, such as disease and pest resistance, Al, Mn and Fe toxicity alleviation, increased P availability, reduced lodging, improved leaf and stalk erectness, freeze resistance, and improvement in plant water economy. This review covers the relationship of silicon to sugarcane crop production, including recommendations on how to best manage silicon in soils and plants, silicon interactions with others elements, and laboratory methodology for determining silicon in the soil, plant and fertilizer. In addition, a future research agenda for silicon in sugarcane is proposed. Silicon Sources The usual carrier for Si is calcium silicate and this material can also supply Ca to a Ca-deficient soil. For fields not fertilized with CaSiO3 for two or more consecutive crops, apply 4.48 t ha-1 CaSiO3 to the current crop if soil Si levels are at or below the critical level of 112 kg ha-1. For fields to which CaSiO3 was applied to one or both of the preceding crops (plant cane and ratoon), apply 2.24 t ha-1 CaSiO3 to the current crop if the soil Si levels are at or below the critical level of 78 kg ha-1. Thereafter, apply 2.5 t ha-1 to each succeeding crop if soil Si levels fall below 78 kg ha-1. The critical levels for the “Crop log” sheath Si (0.7 %) and the Mn/SiO2 ratio = 75 established by Clements (1965a) remain the same; if sheath Si levels of “Crop Log” samples are less than 0.7% or the sheath Mn/SiO2 ratios are above 75, apply 2.5 t ha-1 of CaSiO3 to the current crop (Hagihara and Bosshart, 1984).

See related topics and documents: Silicon Nutrition and Sugarcane Production.pdf

4.14 Calcium Silicate Recommendations for Sugarcane on Florida Organic Soils

Silicon (Si) is not classified as an essential plant nutrient, but it is considered a beneficial nutrient for sugarcane (Saccharum spp.) and rice (Oryza sativa L.) (Ma et al. 2002; Savant et al. 1999). Yields of both crops are increased when calcium (Ca) silicate slag is applied to soils low in soluble Si (Anderson et al. 1991; Elawad et al. 1982a, b; Fox et al. 1967; Snyder et al. 1986). Raid et al. (1992) measured average increases of 20% in sugarcane yield for two crop years and five cultivars following Ca silicate application at 3 tons/acre. Ca silicate application can benefit both crops in a rice-sugarcane rotation when it is applied prior to planting rice (Anderson et al. 1987). Mechanisms responsible for increased yield may include resistance to lodging through increased mechanical strength of cell walls, resistance to disease and insect damage, reduced water loss through evapotranspiration, improved phosphorus (P) metabolism, and reduced accumulation of toxic concentrations of heavy metals (Datnoff et al. 1997; Savant et al. 1999; Snyder et al. 1986).

See related topics and documents: Calcium Silicate Recommendations for Sugarcane on Florida Organic Soils.pdf

4.15 Benefits from Below: Silicon Supplementation Maintains Legume Productivity under Predicted Climate Change Scenarios

Legumes crops have not received their fair share of silicon research. This is a convincing study showing the strong potential for silicon to dramatically increase plant growth under elevated temperature and CO2 levels in a legume plant. Specifically, increased root nodulation occurred, allowing for more nitrogen to be available to the plant for growth. The authors conclude that silicon shows strong potential as an important nutrient to mitigate the effects of climate change by increasing nodulation under temperature and increased CO2 concentrations.

Abstract:

Many studies demonstrate that elevated atmospheric carbon dioxide concentrations (eCO2) can promote root nodulation and biological nitrogen fixation (BNF) in legumes such as lucerne (Medicago sativa). But when elevated temperature (eT) conditions are applied in tandem with eCO2, a more realistic scenario for future climate change, the positive effects of eCO2 on nodulation and BNF in M. sativa are often much reduced. Silicon (Si) supplementation of M. sativa has also been reported to promote root nodulation and BNF, so could potentially restore the positive effects of eCO2 under eT. Increased nitrogen availability, however, could also increase host suitability for aphid pests, potentially negating any benefit. We applied eCO2 (+240 ppm) and eT (+4◦C), separately and in combination, to M. sativa growing in Si supplemented (Si+) and un-supplemented soil (Si−) to determine whether Si moderated the effects of eCO2 and eT. Plants were either inoculated with the aphid Acyrthosiphon pisum or insect-free. In Si− soils, eCO2 stimulated plant growth by 67% and nodulation by 42%, respectively, whereas eT reduced these parameters by 26 and 48%, respectively. Aphids broadly mirrored these effects on Si− plants, increasing colonization rates under eCO2 and performing much worse (reduced abundance and colonization) under eT when compared to ambient conditions, confirming our hypothesized link between root nodulation, plant growth, and pest performance. Examined across all CO2 and temperature regimes, Si supplementation promoted plant growth (+93%), and root nodulation (+50%). A. pisum abundance declined sharply under eT conditions and was largely unaffected by Si supplementation. In conclusion, supplementing M. sativa with Si had consistent positive effects on plant growth and nodulation under different CO2 and temperature scenarios. These findings offer potential for using Si supplementation to maintain legume productivity under predicted climate change scenarios without making legumes more susceptible to insect pests.

See related topics and documents: Benefits from Below – Silicon Supplementation Maintains Legume Productivity.pdf

5. Forestry

5.1 Tree-ring Chemistry of Declining Sugar Maple in Central Ontario, Canada

Tree-ring size and chemistry of healthy and declining sugar maple (Acer saccharum Marsh.) trees, growing in nutrient-poor soils derived from the Precambrian Shield in Ontario, were used to document historical changes in tree nutrition since the mid-1940s. At Dorset, a site showing extensive decline symptoms which have been observed annually since 1986, a reduction in tree-ring width occurred in rings formed during the 1940s, although after 1950, tree-ring size and concentrations of Ca, Mg and Mn have been constant. Concentrations of Ca (680 mg kg-1) and Mg (100 mg kg-1), however, are among the lowest recorded in sugar-maple wood. At Loring, a site which appears much healthier than Dorset, a reduction in tree-ring width occurred during the 1960s, 20 years later than at Dorset, and was accompanied by substantial reductions in concentrations of Ca and Mg, and in particular Mn. Trace metal or Al toxicity are unlikely to be directly responsible for the decline symptoms. If Loring is representative of healthy looking sugar-maple forests in central Ontario, more extensive visual decline symptoms arising from nutrient deficiencies may occur during the next 20 years.

See related topics and documents: http://www.jstor.org/pss/4314967

5.2 Dendrochemical survey of sugar maple (Acer saccharum Marsh) in south-central Ontario, Canada

A dendrochemical survey of sugar maple (Acer saccharum Marsh) was conducted in south-central Ontario, which encompassed twenty-two sites in areas that both exceeded or were below the published Critical Loads with respect to acid deposition. Areas that exceeded the Critical Load were located remote from point emission sources, but were also characterized by thin, nutrient-poor soils overlying the Precambrian Shield. The pH(aq) of surface soils (A-horizon) was lower at sites on the Precambrian Shield and water-extractable concentrations of Ca decreased exponentially with decreasing soil pH. Significant polynomial relationships between soil pH and soil Ca and sugar maple growth, assessed as cumulative tree-ring growth between 1949 and 1998, explained 40% and 37% of the variation in sugar maple growth respectively, with lowest growth associated with low soil pH and low soil Ca. Furthermore, there was a significant linear relationship between wood Ca concentrations (averaged between 1949 and 1998) and soil pH and concentrations of several trace elements in wood (Mn, Pb, Zn, Cd, Sr and Rb) were greater at low soil pH. Poor sugar maple growth was associated with low wood Ca concentrations and high wood Al levels, which together accounted for 43% of the variation in sugar maple growth in a multiple regression model. None of the other wood chemistry variables contributed significantly to the model. These data suggest that sugar maple grows poorly on acidic soils with low Ca and high Al levels. Although such acidic podzols occur naturally in some areas overlying the Precambrian Shield, if Ca losses due to acid deposition and/or harvesting exceed inputs through weathering and deposition (i.e. exceed Critical Load), sugar maple growth may be adversely affected and ultimately lead to increased incidence of sugar maple decline.

See related topics and documents: https://link.springer.com/article/10.1023/A:1015231526980

5.3 Forest Health And Decline – A report from the 2000

Muskoka Workshop and Field Tour of Experts Forest decline has been observed and studied in the Muskoka area of Ontario for about 20 years. In the summer of 2000, a group of experts gathered for a workshop that focused on recent results and a field tour of damaged areas. This report summarizes the findings and conclusions from the information assembled at the workshop. Six recent assessments and several scientific reviews of forest decline/health research and monitoring were examined. From these reports, the group found that acid rain and other air pollutants damage forests by a number of established mechanisms. Nutrient deficiency in soils: A dominant mechanism for damages from sulphur and nitrogen deposition is nutrient deficiency caused by leaching of calcium and magnesium from the soil, leading to decreased growth, canopy decline, and increased tree mortality. Nutrient imbalance caused by leaching of calcium and magnesium from soils has been reversed in experiments conducted in Quebec, where dolomitic limestone was added to the soil under declining sugar maple trees. The experimental treatment increased tree growth rate within one year and stopped the progression of decline symptoms of the trees over the four-year study period. Damage to vegetation by acidic fogs: Acid fogs have caused extensive dieback of white birch on the shores of the Bay of Fundy. Fog duration varies from year to year and there is a linear relationship between hours of fog from June to August and the mean percentage of foliar browning. Such fogs also prevent the germination of the pollen of white and mountain paper birch. Acid fogs reduce the frost hardiness of exposed red spruce. Increased occurrence of insects and diseases: In a study of four areas of the northeastern United States, the areas with the greatest frequency of problems from forest insects and disease also receive the highest deposition of sulphur and nitrogen and/or have the highest annual exposure to ground-level ozone. Such a relationship is compatible with the role of strong anion deposition in depleting available pools of cations, notably calcium, from the relatively low soil pools in these forests. Damage from nitrogen deposition: Nitrogen deposition can degrade forest ecosystems by increasing sensitivity to frost, reducing net primary production, and leaching of nutrients, especially in areas where soil nitrogen levels are high and have reached or are approaching saturation. In addition to these mechanisms, other factors are cause for concern for the future of forests affected by acid rain.

See related topics and documents: Forest Health And Decline-A Report From The 2000 Muskoka Workshop And Field Tour of Experts.pdf

5.4 Decline Of Sugar Maples

Sugar maples across the northeastern US and eastern Canada are in decline. The problem is not new, but the incidence and severity of maple decline have increased markedly in recent decades to include urban, sugarbush, and forest environments (Horsley et al., 2002). The exact causes of sugar maple decline are hard to pinpoint. The current consensus is that maple decline is a progressive disease condition that begins when the trees are altered initially by stress and continues as they become invaded by organisms of secondary action (Bauce and Allen, 1992). It is the activity of these secondary pathogens on an already weakened tree that eventually leads to the death of the tree. Sugar maple decline does not spread like a disease, but if one tree is affected because of environmental conditions, chances are that other trees near it are, or will become, affected. Drohan et al. (2002) found that foliage from declining plots had significantly lower base cations (K, Ca, and Mg) and higher Mn as compared to that from non-declining plots. Soils in declining plots had lower base cations and pH, a Ca:Al ratio of less than or equal to 1, lower percent clay, and higher percent sand and rock fragments than soils on nondeclining plots. Studies that have examined the effects of altering the soil pH on the progress of maple decline have yielded mixed results. Liming (e.g. Moore et al., 2000) and K fertilization (Ouimet and Fortin, 1992) increase the vigor and growth of sugar maple in an acid soil, poor in available Ca and Mg. Four years after the lime application, improvements in foliar concentrations of N, P, Ca, and Mg were noted. Liming also increased the radial growth of sugar maple compared with control trees.

See related topics and documents: The Decline of Sugar Maples.pdf

5.5 Terrestrial Liming As a Restoration Technique for Acidified Forest Ecosystems

We studied the effects of liming on soils and forest songbirds as well as vegetation and calcium-rich invertebrate prey variables that were predicted to link birds to changes in soil conditions. We observed increases in soil pH, calcium, and magnesium, as well as in songbird abundances in response to lime application, with continuing increases through five years after liming. We observed an overall increase in snail abundance on limed sites, but an initial peak of a 23 fold increase three years after liming was reduced to an 11 fold increase five years after liming. We observed an increase in forb ground cover on limed sites, but liming had no effect on millipede abundance or other vegetation measures. Of the variables we measured, snail abundance was the most likely mechanism for the response in bird abundances. Because we observed continued benefits of liming up to five years post-treatment, we concluded that liming is a very promising technique for restoring forest ecosystems impacted by acidic deposition. Discussion: We observed beneficial effects of liming at multiple ecosystem levels five years after lime was applied to study areas within and acidified forest and gained a better understanding of the links between soil conditions and other components of the forest ecosystem. With data from an additional two years after liming since our preliminary report [19], we continued to observe increases in soil pH, calcium availability, and bird abundance. We also observed unexpected results, with snail abundance initially increasing and then decreasing, although still remaining significantly more abundant than prior to liming. Some components of the forest ecosystem (e.g., millipede abundance and vegetation) did not respond or responded too slowly to liming to be observed in five years. These combined responses to liming indicate a strong bottom-up influence of soil nutrients in an acidified forest and a link between soil conditions and songbird abundance. Soils: The continued increases observed in soil pH, calcium, and magnesium five years after liming are promising and agree with other liming studies that one application of lime can continue to improve and maintain improved soil condition for a long time. In other studies, continued increases in these soil parameters have been observed beyond five years after dolomitic limestone application [10]. Also, based on models, dolomitic lime application is predicted to elevate soil-base cation levels for up to 50 years, with continued increases in the first 15 to 20 years, followed by a gradual decline [12]. The increases in soil pH brought average soil condition from below 4.0, which is considered too low to maintain healthy oak forests, to 4.7 and never exceeded normal soil conditions for forest soils in the area (no soils with pH > 7.0) [33]. Potential negative effects of liming on soils include decreases in potassium, resulting from displacement by Mg and Ca, and decreased phosphorus, resulting from the formation of insoluble Ca phosphates or uptake by plants [34–36]. Unlike in other liming studies, we observed no substantial effects of dolomitic lime application on soil P or K [10, 37].

See related topics and documents: Terrestrial Liming As a Restoration Technique for Acidified Forest Ecosystems.pdf

5.6 Calcium Silicate key to restoring forests

Adding calcium to the soil can help to reverse the decades-long decline of forests damaged by acid rain, according to a paper published in Environmental Science and Technology Letters

The paper presents the findings from a 15-year study of trees in the Hubbard Brook Experimental Forest in New Hampshire. In 1999, 40 tonnes of calcium silicate pellets were dispersed by helicopter over a 12-hectare section of the forest in which the trees showed declining growth rates and a high rate of unexpected deaths. Previous soil analysis had showed that it had half the normal level of calcium.

Researchers from the University of California, Berkeley and Syracuse University found that trees in the calcium-treated site grew more healthily, producing 21 percent more wood and 11 percent more leaves, when compared to trees that grew in a nearby control site.

‘It’s generally accepted that acid rain harms trees, but the value of our study is that it proves the causal link between the chronic loss of soil calcium caused by decades of acid rain and its impact on tree growth,’ said John Battles of UC Berkeley, who led the study. ‘The temporal and spatial scope of the study – 15 years and entire watersheds – is unique and makes the results convincing.’

November 2013, National Geographic (Article unavailable)

Related research papers:
Restoring soil calcium reverses forest decline.pdf
Decreased water flowing from a forest amended with calcium silicate.pdf
Soil chemical dynamics after calcium silicate addition to a northern hardwood forest

5.7 Photo Essay Of The Wollastonite Addition On Watershed 1 At Hubbard Brook

A photographic account of the application of wollastonite to sensitive forest and wetlands via helicopter aerial seeding.

Pictures: Photo essay of wollastonite application of Watershed 1.jpg
Archived website: Watershed 1 at Hubbard Brook:Calcium addition in October 1999

5.8 Calcium Watershed Addition

In this study, we propose to investigate the role of Ca2+ in regulating the structure and function of a northern hardwood forest. This will be accomplished by the experimental addition of wollastonite (CaSiO3), a readily weatherable Ca-silicate mineral, to watershed 1 (w1) at the HBEF. The dissolution of wollasonite will supply Ca2+, H4SiO4 and acid neutralizing capacity (ANC) to solution:

CaSiO3 + H2O + 2H+ = Ca2+ + H4SiO4

Observation

We suggest that supplying Ca2+ by the dissolution of a silicate mineral that is similar to the natural weathering source of this element in forest ecosystems throughout the Northeast is a much more experimentally sound treatment than adding CaCO3, as has been done in several previous studies (Adams and Dickson 1973; Nihlgard et al. 1988). Moreover, the wollastonite that we will use in this study has a distinct 87Sr/86Sr ratio compared to other sources at Hubbard Brook (e.g., precipitation, weatherable minerals). This stable isotopic tracer will enable us to trace the fate of the added Ca2+ in the ecosystem with exceptionally high sensitivity.

See related topics and documents: Calcium Watershed Addition.htm

5.9 Establishment of Calcium Silicate Treatment Plots on the Forests at Hubbard Brook, Bartlett, and Jeffers Brook

During the fall of 2011, plots in six stands of the MELNHE project were treated with calcium in the form of wollastonite (CaSiO3). The stands are in the Bartlett Experimental Forest (BEF), Hubbard Brook Experimental Forest (HBEF), and Jeffers Brook area. Adding Ca plots to the experiment was motivated by the established importance of Ca to the ecological functioning of forests in the White Mountains (Federer et al. 1989, Likens et al. 1996, Hamburg et al. 2003), including the recently-described increase in whole-watershed transpiration after the wollastonite experiment at the HBEF (Green et al., in preparation).

See related topics and documents: Establishment of Calcium Silicate Treatment Plots on the Forests at Hubbard Brook, Bartlett, and Jeffers Brook – Dec 2011.pdf

5.10 Summary Of The Wollastonite (CaSiO3) Addition To Watershed 1 At The Hubbard Brook Experimental Forest

Objective: The objective of the Watershed 1 (W1) manipulation at the Hubbard Brook Experimental Forest (HBEF) is to evaluate the role of Ca supply in regulating the structure and function of base-poor forest and aquatic ecosystems.

Method: The Ca content of soil was increased through the application of wollastonite (CaSiO3). The application rate of 1.2 metric tonnes Ca/ha was intended to increase the current base saturation of the soil from 10% to 19%. This latter value is thought to have been the base saturation of soil at the HBEF 50 years ago, before the advent of acidic deposition.

See related topics and documents: Wollastonite application of Watershed.htm

5.11 Changes in soil chemistry following a watershed-scale application of wollastonite (CaSiO3) at Hubbard Brook, New Hampshire, USA

Decades of acidic deposition in the northeastern United States is believed to have caused the loss of substantial amounts of calcium from forest soils. This process of ‘calcium depletion’ affected the chemistry of drainage waters in the region and may have impacted forest health. To study this phenomenon, we applied 45 Mg of wollastonite (1316 kg Ca ha-1) to watershed 1 (W1) at the Hubbard Brook Experimental Forest, in New Hampshire, USA in October, 1999. Exchangeable Ca (1 M NH4Cl) and soil pH increased significantly in the Oie and Oa horizons, and in the top 10 cm of the mineral soil, in samples collected 1, 3, and 7 years after treatment. Exchangeable acidity (1 M KCl) decreased significantly in the Oie and Oa horizons after treatment, but the effect in the upper mineral soil was not clear. Base saturation and effective cation exchange capacity (CECe) increased significantly after wollastonite application in all layers studied, primarily on the strength of the increased exchangeable Ca. We did not observe compensatory decreases in exchangeable Al, or other exchangeable cations, as initially hypothesized. Therefore, while wollastonite addition has improved the base status of W1 soils, it has not resulted in decreases in exchangeable Al.

Conclusions: Wollastonite addition resulted in persistent increases in the base status of soils at Hubbard Brook. Our results suggest that wollastonite may be a good alternative to traditional lime as a potential amendment for acidified soils in the northeastern United States. Wollastonite appears to offer a long-lasting release of Ca without the alkalinity ‘shock’ produced by lime.

See related topics and documents: Changes in soil chemistry following a watershed-scale application of wollastonite.pdf

5.12 Soil Chemical Dynamics after Calcium Silicate Addition to a Northern Hardwood Forest

Acidic deposition has resulted in the loss of available soil Ca from base-poor soils in the northeastern United States. In 1999, wollastonite (CaSiO3) was experimentally added to a watershed at the Hubbard Brook Experimental Forest in New Hampshire in an attempt to restore the base saturation of the soil to its estimated pre-acidification level. We measured the total Ca in the O horizon and the top 10 cm of mineral soil to track the fate of the added Ca. We also measured soil pH and exchangeable cations to assess the impact of the treatment on soil acidity. In the first 11 yr after treatment, Ca was transported downward through the forest floor and upper mineral soil in a progressive fashion. By Year 11, at least 650 kg ha−1 of the 1028 kg ha−1 of Ca that was added to the watershed was no longer in the O horizon or the top 10 cm of mineral soil. Soil pH and exchangeable Ca concentrations increased significantly in organic and mineral soils after treatment. Exchangeable H and Al concentrations decreased significantly. The pool of exchangeable Ca increased significantly after treatment, peaking in the O horizons 3 yr after treatment and in the upper mineral soil 7 yr after treatment. The pools of exchangeable Al and H steadily and significantly decreased through the study period. Only about 3% of the added Ca was exported from the watershed in stream water after 11 yr. Wollastonite treatment was thus an effective means of increasing available pools of Ca in this forest ecosystem.

See related topics and documents: Soil Chemical Dynamics after Calcium Silicate Addition to a Northern Hardwood Forest.pdf

5.13 Dissolution Of Wollastonite During The Experimental Manipulation Of Hubbard Brook Watershed 1

Powdered and pelletized wollastonite (CaSiO3) was applied to an 11.8 ha forested watershed at the Hubbard Brook Experimental Forest (HBEF) in northern New Hampshire, U.S.A. during October of 1999. The dissolution of wollastonite was studied using watershed solute mass balances, and a 87Sr/ 86Sr isotopic tracer. The wollastonite (87Sr/86Sr = 0.70554) that was deposited directly into the stream channel began to dissolve immediately, resulting in marked increases in stream water Ca concentrations and decreases in the 87Sr/86Sr ratios from pre-application values of 0.872 mg/L and 0.72032 to values of _2.6 mg/L and 0.71818 respectively. After one calendar year, 401 kg of the initial 631 kg of wollastonite applied to the stream channel was exported as stream dissolved load, and 230 kg remained within the stream channel as residual CaSiO3 and/or adsorbed on streambed exchange sites. Using previously established values for streambed Ca exchange capacity at the HBEF, the dissolution rate for wollastonite was found to be consistent with dissolution rates measured in laboratory experiments. Initially, Ca was released from the mineral lattice faster than Si, resulting in the development of a Ca depleted leached layer on mineral grains. The degree of preferential Ca release decreased with time and reached stoichiometric proportions after _6 months. Using Sr as a proxy for Ca, the Ca from wollastonite dissolution can be accurately tracked as it is transported through the aquatic and terrestrial ecosystems of this watershed.

Conclusions: The application of wollastonite to a forested watershed within the HBEF presents the opportunity to observe the dissolution of a well-studied silicate mineral in a natural environment. Stream Ca concentrations could be accurately attributed to either wollastonite dissolution or stream water background using the distinct 87Sr/86 Sr and Ca/Sr ratios of both the background stream water and the applied wollastonite.

After accounting for cation exchange within the stream channel bed materials, the dissolution rate determined in laboratory experiments is consistent with observed changes in stream chemistry as a result of the wollastonite application.

The analysis of Ca and Si from wollastonite dissolution suggests preferential release of Ca over Si in the initial stages of weathering, followed by a period of stoichiometric release, and finally a period of preferential Si release. This observation supports previous laboratory experimental results that demonstrated the development of a Ca-depleted surface layer during initial stages of mineral dissolution.

The proportion of Ca from wollastonite dissolution in any ecosystemm component can be quantified using the 87Sr/86Sr and Ca/Sr ratios. Thus, the movement of Ca released by wollastonite dissolution can be traced through the aquatic and terrestrial ecosystems, allowing us to study the pathways and rates of Ca transfer.

See related topics and documents: Dissolution of wollastonite during the experimental manipulation of Hubbard Brook Watershed.pdf

5.14 Effects of a whole-watershed calcium addition on the chemistry of stream storm events at the Hubbard Brook Experimental Forest in NH, USA

Patterns of storm runoff chemistry from a wollastonite (calcium-silicate mineral, CaSiO3) treated watershed (W1) were compared with a reference watershed (W6) at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire (NH), USA to investigate the role of Ca2+ supply in the acid–base status of stream chemistry.

In the summer of 2003, six storm events were studied in W1 and W6 to evaluate the effects of the wollastonite treatment on the episodic acidification of stream waters. Although mean values of Ca2+ concentrations decreased slightly from 33.8 to 31.7 μmol/L with increasing stream discharge in W1 during the events, the mean value of acid neutralizing capacity (ANC) was positive (1.2 μeq/L) during storm events, compared to negative values (−0.2 μeq/L) in W6. This pattern is presumably due to enhanced Ca2+ supply in W1 (20.7 to 29.0% of dissolved Ca2+ derived from the added wollastonite) to stream water as a result of interflow along shallow flowpaths. In addition, the application of wollastonite increased pH and dissolved silica (H4SiO4) concentrations, and decreased the concentration of inorganic monomeric Al (Ali) in W1 in comparison with W6 during storm events. Despite an increase in SO4 2− concentration, likely due to desorption of sulfate from soil after the treatment, the watershed showed an increase in ANC compared to the reference watershed, serving to mitigate episodic acidification.

See related topics and documents: The effects of a whole-watershed calcium addition on the chemistry of stream storm revents.pdf

5.15 Decreased water flowing from a forest amended with calcium silicate (Wollastonite)

Acid deposition during the 20th century caused widespread depletion of available soil calcium (Ca) throughout much of the industrialized world. To better understand how forest ecosystems respond to changes in a component of acidification stress, an 11.8-ha watershed was amended with wollastonite, a calcium silicate mineral, to restore available soil Ca to preindustrial levels through natural weathering. An unexpected outcome of the Ca amendment was a change in watershed hydrology; annual evapotranspiration increased by 25%, 18%, and 19%, respectively, for the 3 y following treatment before returning to pretreatment levels. During this period, the watershed retained Ca from the wollastonite, indicating a watershed-scale fertilization effect on transpiration. That response is unique in being a measured manipulation of watershed runoff attributable to fertilization, a response of similar magnitude to effects of deforestation. Our results suggest that past and future changes in available soil Ca concentrations have important and previously unrecognized implications for the water cycle.

See related topics and documents: Decreased water flowing from a forest amended with calcium silicate.pdf

5.16 Field Work for Transpiration Research Project Center for the Environment – Plymouth State University.website

In the fall of 1999, wollastonite (CaSiO3) was applied to a watershed at the Hubbard Brook Experimental Forest (HBEF). This appears to have stimulated ~20% of additional transpiration for three years. This unexpected response has been recently studied by CFE’s Mark Green and colleagues. The physiological cause of the increased transpiration or the transience of the response are not well understood because detailed data addressing forest transpiration were not collected.

A new fertilization study is beginning at the HBEF, Bartlett Experimental Forest, and at Jeffers Brook on the impacts of additional nitrogen, phosphorus, and calcium to forest dynamics. This study had not intended on collecting transpiration data, but given the recent discovery of the whole watershed transpiration response to wollastonite addition, Mark received funding from the National Science Foundation to fertilize forested research plots with wollastonite and collaborate with Michele Pruyn to collect sap flow data that will inform mechanisms responsible for the watershed 1 response to wollastonite addition.

See related topics and documents: https://campus.plymouth.edu/cfe/field-work-for-transpiration-research-project/

5.17 Regeneration ecology of sugar maple (Acer saccharum): seedling survival in relation to nutrition, site factors, and damage by insects and pathogens

The possible regeneration failure of sugar maple (Acer saccharum Marsh.) as part of their decline has been not well explored using field studies. We sought to clarify the roles of maternal effects and dynamics of early-season survival in contributing to the previously documented pattern of larger seedlings and higher seedling densities on a Ca-treated watershed (CAL) at Hubbard Brook Experimental Forest. We used a reciprocal seed planting experiment at four sites, two sites per watershed blocked by elevation. Regardless of maternity, sugar maple seedlings planted in CAL had higher survival than seedlings in the reference watershed. However, this advantage was not as clearly linked to the Ca amendment as in our previous work, probably, in part, because Ca availability has decreased over time. Maternal effects on seed chemistry and some seedling traits were detected, but these were not strong determinants of survival. Site was a good predictor of early seedling survival with litter layer depth, pathogen prevalence, and soil chemistry all contributing to the explanatory power of site. The strength of Ca,addition effects on sugar maple regeneration from seed depends on initial soil characteristics, application amounts, and interactions of the amendment with other factors such as leaf litter cycling, weather, and pathogens.

See related topics and documents: Regeneration ecology of sugar maple.pdf

5.18 Response Of Sugar Maple To Calcium Addition To Northern Hardwood Forest

Watershed budget studies at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, have demonstrated high calcium depletion of soil during the 20th century due, in part, to acid deposition. Over the past 25 years, tree growth (especially for sugar maple) has declined on the experimental watersheds at the HBEF. In October 1999, 0.85 Mg Ca/ha was added to Watershed 1 (W1) at the HBEF in the form of wollastonite (CaSiO3), a treatment that, by summer 2002, had raised the pH in the Oie horizon from 3.8 to 5.0 and, in the Oa horizon, from 3.9 to 4.2. We measured the response of sugar maple to the calcium fertilization treatment on W1.

Foliar calcium concentration of canopy sugar maples in W1 increased markedly beginning the second year after treatment, and foliar manganese declined in years four and five. By 2005, the crown condition of sugar maple was much healthier in the treated watershed as compared with the untreated reference watershed (W6). Following high seed production in 2000 and 2002, the density of sugar maple seedlings increased significantly on W1 in comparison with W6 in 2001 and 2003. Survivorship of the 2003 cohort through July 2005 was much higher on W1 (36.6%) than W6 (10.2%). In 2003, sugar maple germinants on W1 were ;50% larger than those in reference plots, and foliar chlorophyll concentrations were significantly greater (0.27 g/m2 vs. 0.23 g/m2 leaf area). Foliage and fine-root calcium concentrations were roughly twice as high, and manganese concentrations twice as low in the treated than the reference seedlings in 2003 and 2004. Mycorrhizal colonization of seedlings was also much greater in the treated (22.4% of root length) than the reference sites (4.4%). A similar, though less dramatic, difference was observed for mycorrhizal colonization of mature sugar maples (56% vs. 35%).

These results reinforce and extend other regional observations that sugar maple decline in the northeastern United States and southern Canada is caused in part by anthropogenic effects on soil calcium status, but the causal interactions among inorganic nutrition, physiological stress, mycorrhizal colonization, and seedling growth and health remain to be established.

See related topics and documents: Response of Sugar Maple to Calcium Addition in Northern Hardwood Forest.pdf

5.19 Watershed 1 calcium addition: response of sugar maple – 2007

Element budget studies using the small watershed approach at the HBEF demonstrated the magnitude of soil calcium depletion from these forest ecosystems that resulted from the combination of forest harvest and acid deposition during the 20th century. As a result, surface water acidification has occurred and over the past 25 years tree growth appears to have declined. In October 1999 0.85 Mg Ca/ha was added to experimental Watershed 1 in the form of the silicate mineral wollastonite (photos, right), with the objective of returning the calcium status and pH of the soil to pre-20th century levels over the following decade. By summer 2002 the treatment had raised the pH of the Oa horizon soil (humus layer) from 3.9 to 4.2.

Foliar Ca concentration of canopy sugar maples in W1 increased markedly beginning the second year after treatment and by 2005, the crown condition of sugar maple was much healthier in the treated watershed as compared with untreated reference watershed (W6). Following high seed production in 2000 and 2002, the density of sugar maple seedlings increased significantly on W1 in comparison with W6 in 2001 and 2003. Survivorship of the 2003 cohort through July 2005 was much higher on W1 (36.6%) than W6 (10.2%). Sugar maple germinants on W1 were about 50% larger than those in reference plots and foliage and fine root Ca concentrations were roughly twice as high. Mycorrhizal colonization of seedlings also was much greater in the treated (22.4% of root length) than the reference sites (4.4%). These results reinforce and extend other regional observations that sugar maple decline in the northeastern United States and southern Canada is caused in part by anthropogenic effects on soil Ca status, but the causal interactions among inorganic nutrition, physiological stress, mycorrhizal colonization and seedling growth and health remain to be established.

See related topics and documents: Watershed 1 calcium addition-fahey07.pdf

5.20 Calcium Fertilization Effects on Leaf Biochemistry of Northern Hardwood Trees

Acidic deposition has caused a depletion of calcium in Northern Forest soils. Calcium plays a vital role in the growth and productivity of forest trees. Several studies have demonstrated that calcium and other essential cations (ions with a positive charge) are available in less-than-adequate quantities in various forest ecosystems in the United States, including the Hubbard Brook Experimental Forest, a Long Term Ecological Research site in New Hampshire. An interdisciplinary team of scientists from institutions in New Hampshire, Vermont, Connecticut, New York, and Michigan established a long term study in which wollastonite (calcium silicate) was added to watershed 1 (WS1) at Hubbard Brook in 1999 to evaluate its effects on forest ecosystem functions. NSRC researchers analyzed the effects of calcium addition on soluble ions, chlorophyll, polyamines, and amino acids in tree foliage of three hardwood species (sugar maple, yellow birch, and American beech). They further examined these effects in relation to elevation at calcium-supplemented WS1 and untreated WS3 watersheds.

Foliar soluble calcium increased significantly in all species at mid and high elevations at calcium-supplemented WS1. This was accompanied by increases in soluble phosphorus, chlorophyll, and two amino acids, glutamate and glycine. Researchers also observed a decrease in other amino acids that are known metabolic indicators of physiological stress. In general, these changes were species-specific and were dependent on elevation. Comparison of metabolic data from these three species reinforces earlier findings that sugar maple is the most sensitive and American beech the least sensitive species to soil calcium limitation, and there was an increase in sensitivity with an increase in elevation.

See related topics and documents: Calcium Fertilization Effects on Leaf Biochemistry.pdf

5.21 Calcium Addition At The Hubbard Brook Experimental Forest Increases Sugar Storage, Antioxidant Activity And Cold Tolerance In Native Red Spruce

In fall (November 2005) and winter (February 2006), we collected current-year foliage of native red spruce (Picea rubens Sarg.) growing in a reference watershed and in a watershed treated in 1999 with wollastonite (CaSiO3, a slow release calcium source) to simulate preindustrial soil calcium concentrations (Ca-addition watershed) at the Hubbard Brook Experimental Forest (Thornton, NH). We analyzed nutrition, soluble sugar concentrations, ascorbate peroxidase (APX) activity and cold tolerance, to evaluate the basis of recent (2003) differences between watersheds in red spruce foliar winter injury. Foliar Ca and total sugar concentrations were significantly higher in trees in the Ca-addition watershed than in trees in the reference watershed during both fall (P = 0.037 and 0.035, respectively) and winter (P = 0.055 and 0.036, respectively). The Ca-addition treatment significantly increased foliar fructose and glucose concentrations in November (P =0.013 and 0.007, respectively) and foliar sucrose concentrations in winter (P = 0.040). Foliar APX activity was similar in trees in both watersheds during fall (P = 0.28), but higher in trees in the Ca-addition watershed during winter (P = 0.063). Cold tolerance of foliage was significantly greater in trees in the Ca-addition watershed than in trees in the reference watershed (P < 0.001). Our results suggest that low foliar sugar concentrations and APX activity, and reduced cold tolerance in trees in the reference watershed contributed to their high vulnerability to winter injury in 2003. Because the reference watershed reflects forest conditions in the region, the consequences of impaired physiological function caused by soil Ca depletion may have widespread implications for forest health.

See related topics and documents: Calcium addition at the Hubbard Brook Experimental Forest increases sugar storage, antioxidant activity and cold tolerance in native red spruce (Picea rubens).pdf

5.22 Four Times the Timber Volume for a Forest in Central Europe

The Barvarian Research and Experimental Institute for Forestry, Munich, Germany, 1986. Summary of the four page German study translated by Christian Campe. The original German version is available in the Forestry Research Packet through mail order.

This report contains information on fertilization with rock dust and its practical application. The widely used term “gesteinsmehl” refers to pulverized silicate rocks.

Results of the study showed:

• After 24 years the wood volume of the treated area was four times higher than in the untreated area.
• In the case of new pine seedlings remineralized with basalt rock dust, there were gains over the untreated area after the sixth year.
  The advantage only began to taper off after 60 years.

See related topics and documents: Four Times the Timber Volume for a Forest in Central Europe.pdf

 

5.23 Response of citrus to silicon soil amendments

While citrus may seem a ways off for some climates, this study shows the versatility of calcium silicates across a wide range of tree species. Increased tree vigour and root growth are clearly noted benefits.  Wollastonite has similar levels as magnesium, calcium and silicon as slag and is much cleaner with low and acceptable levels of heavy metals for long-term use.

Abstract:
Silicon (Si) is a basic mineral forming element and a beneficial nutrient for higher plants. Fertilization with soil amendments containing chemically activated Si has an effect on physical and chemical soil properties, including increased soil exchange capacity, improved water and air regimes, reduced Al, heavy metal and organic pollutant toxicities, optimized pH level of soil, and maintenance of nutrients in plant-available form. Improving plant Si nutrition has been shown to reinforce plant protection properties against diseases, in-sects, and other unfavorable conditions. Improving Si nutrition also aids in the initiation of root and fruit formation in higher plants. The object of this investigation was to deter-mine the response of citrus growing in South Florida to a Si soil amendment consisting of Ca-Mg slag. Both field and greenhouse experiments were conducted. A comparative study was made of Si compounds in the soil and of the Si status of citrus leaves. The resulting data showed that sandy soils are low in bio-geochemically active Si. A relationship was determined between the soil Si status and the leaf Si content and also tree vigor of ‘Valencia’ orange [Citrus sinensis (L.) Os-beck]. Optimization of Si nutrition was responsible for a significant increase in the mass of roots and green mass of germinated ‘Marsh’ grapefruit (Citrus paradisi Macf.) seedlings.

Here’s the full study: Response of citrus to silicon soil amendments.pdf

6. Disease suppression

6.1 Silicon Suppresses Fusarium Crown and Root Rot of Tomato

Abstract
Fusarium oxysporum f.sp. radicislycopersici, the causal agent of Fusarium crown and root rot (FCRR), is a serious soil-borne disease of tomato. Soil fumigation and host resistance may reduce the impact of this disease, but other alternative management strategies are needed because these options may not always be available or effective. The purpose of this study was to determine the potential of silicon (Si) to reduce the disease severity of FCRR. Seven-day-old seedlings of Bonny Best tomato, susceptible to FCRR, were transplanted in sand culture amended with HoaglandÕs nutrient solution with (+Si) or without ()Si) 100 mg Si ⁄ l. At 3 weeks after transplanting, three inoculum concentrations 0, 106 and 107 conidia ⁄ plant were used to inoculate the seedlings. Disease severity and silicon concentration were evaluated at 4 weeks after inoculation. Disease progress over time was investigated using the seedlings amended with Si or without Si and inoculated with 0 or 106 conidia ⁄ plant. Disease severity was evaluated at 2, 3, 4 and 6 weeks after inoculation. After rating disease, evaluated plants were divided into shoots and roots for silicon concentration analysis. Si significantly reduced the severity of FCRR on the stem of tomato at 4 weeks after inoculation. Results of disease progress suggested that the decrease in the disease severity of FCRR by Si amendment was probably due to a delay in onset in initial infection of roots and the movement of the pathogen from roots to stems. Si contents of roots and shoots were significantly higher in tomato plants supplied with Si than in those without Si. Moreover, the increase in the Si content of roots was significantly correlated with the reduction of disease severity of root, crown and stem, indicating a silicon-mediated resistance. Supplying Si to tomato seedlings can reduce the disease severity of FCRR, providing an alternative disease management strategy.

See related topics and documents: Fusarium Crown and Root Rot of Tomato.pdf

6.2 Silicon and plant disease resistance against pathogenic fungi

Abstract:
Silicon (Si) is a bioactive element associated with beneficial effects on mechanical and physiological properties of plants. Silicon alleviates abiotic and biotic stresses, and increases the resistance of plants to pathogenic fungi. Several studies have suggested that Si activates plant defence mechanisms, yet the exact nature of the interaction between the element and biochemical pathways leading to resistance remains unclear. Silicon possesses unique biochemical properties that may explain its bioactivity as a regulator of plant defence mechanisms. It can act as a modulator influencing the timing and extent of plant defence responses in a manner reminiscent of the role of secondary messengers in induced systemic resistance; it can also bind to hydroxyl groups of proteins strategically involved in signal transduction, or it can interfere with cationic co-factors of enzymes influencing pathogenesis-related events. Silicon may, therefore, interact with several key components of plant stress signalling systems leading to induced resistance. Ó 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

See related topics and documents: Silicon and plant disease resistance against pathogenic fungi.pdf

6.3 Applying Wollastonite to Soil to Adjust pH and Suppress Powdery Mildew on Pumpkin

Although not considered an essential nutrient, silicon (Si) can be beneficial to plants. Si accumulator species such as pumpkin (Cucurbita pepo var. pepo) can absorb Si from soil. Si uptake may reduce plant susceptibility to fungal diseases such as cucurbit powdery mildew (Podosphaera xanthii and Erysiphe cichoracearum). We previously reported that wollastonite, an Organic Materials Reviews Institute– approved natural mineral, can increase soil Si level, increase soil pH, provide pumpkin plants with Si, and increase their resistance to powdery mildew. In this study, we examined the optimum application rate of wollastonite for pumpkins grown in pots and exposed to cucurbit powdery mildew. We confirmed that wol- lastonite has liming capabilities similar to regular limestone. Regardless of the application rates, wollastonite and limestone showed similar effects on soil chemistry and plant mineral composition. Pumpkin plants grown with the lower doses of wollastonite amendments (3.13 and 6.25 tons/acre) had the greatest tissue Si concentrations and demonstrated the greatest disease resistance. We conclude that wollastonite is a useful material for organic cucurbit (Cucurbitaceae) growers who want to increase soil pH and improve plant resistance to powdery mildew at the same time. Applying wollastonite at rates beyond the amount required to achieve a desirable soil pH for pumpkin production did not further increase Si uptake, nor did it further suppress powdery mildew development.

See full article: Applying Wollastonite to Soil to Adjust pH and Suppress Powdery Mildew on Pumpkin.pdf

 

7. Cabon Sequestration

Read more about carbon sequestration and wollastonite in the Environmental Research section.

7.1 CO2 sequestration by wollastonite-amended agricultural soils – An Ontario field study

Terrestrial enhanced weathering is the spreading of silicate powder on land, and can sequester atmospheric CO2 through carbonation of calcium- and magnesium-rich minerals. When applied to soils, at suitable geochemical conditions, alkaline minerals lead to the accumulation of soil inorganic carbon as pedogenic carbonates. Agricultural land covers 37 % of the Earth’s land surface, thus offering a natural sink for atmospheric CO2. Wollastonite (CaSiO3) has been commercialized in Ontario as an agricultural soil amendment for several years, but it is not known if or how much CO2 is sequestered annually. In the present study, wollastonite-amended soils were collected from three commercial-scale fields located in Ontario: a leafy vegetable farm in the town of Paris (Field 1); a potato farm in the settlement of Alliston (Field 2); and a soybean farm in the city of Woodstock (Field 3). Chemical and mineralogical assessments of these soils were conducted to determine their carbonate content and the fate of the wollastonite. The soil inorganic carbon (SIC) content was higher in all soils that had been amended with wollastonite, compared to controls, and in Field 1 the SIC content was 2.6 times higher in soil amended thrice with wollastonite compared to a single application. Mineralogical analysis showed the presence of additional polymorphs of SiO2, which may originate from the wollastonite after the dissolution of calcium. This work provides further evidence, here for the first time at a regional scale, that soil amendment with alkaline silicates can be an effective geoengineering tool for climate change mitigation.

See full article: CO2 sequestration by wollastonite-amended agricultural soils – An Ontario field study.pdf

7.2 Urban Farming with Enhanced Rock Weathering As a Prospective Climate Stabilization Wedge

With no single carbon capture and sequestration solution able to limit the global temperature rise to 1.5−2.0 °C by 2100, additional climate stabilization measures are needed to complement current mitigation approaches. Urban farming presents an easy-to-adopt pathway toward carbon neutrality, unlocking extensive urban surface areas that can be leveraged to grow food while sequestering CO2. Urban farming involves extensive surface areas, such as roofs, balconies, and vertical spaces, allowing for soil presence and atmospheric carbon sequestration through air-to-soil contact. In this viewpoint we also advocate the incorporation of enhanced rock weathering (ERW) into urban farming, providing a further opportunity for this recognized negative emissions technology that is gaining momentum worldwide to gain greater utilization.

See full article: Urban Farming with Enhanced Rock Weathering As a Prospective Climate Stabilization Wedge

7.3 How Adding Rock Dust to Soil Could Help Get Carbon into the Ground – Yale E360

This is a profile of research in progress and references Canadian Wollastonite sponsored research carried out at the University of Guelph.

Researchers are finding that when pulverized rock is applied to agricultural fields, the soil pulls far more carbon from the air, and crop yields increase. More studies are underway, but some scientists say this method shows significant benefits for farmers and the climate.

See full article: How Adding Rock Dust to Soil Could Help Get Carbon into the Ground – Yale E360

7.4 Alkaline Mineral Soil Amendment: A Climate Change ‘Stabilization Wedge’

Extreme climate change due to heat-trapping gases, especially carbon dioxide, necessitates its mitigation. In this context, the carbon dioxide sequestration technology of enhanced weathering has for years been investigated, with a possible implementation strategy via alkaline mineral soil amendment being more recently proposed. Candidate materials for enhanced weathering include calcium and magnesium silicates, most notably those belonging to the olivine, pyroxene and serpentine groups of minerals, given their reactivity with CO2 and global availability. When these finely crushed silicate rocks are applied to the soil, the alkaline earth metal cations released during mineral weathering gradually react with carbonate anions and results in the formation of pedogenic carbonates, which, over time, and under the right conditions, can accumulate in the soil. This review paper critically reviews the available literature on alkaline mineral soil amendments and its potential to sequester enough CO2 to be considered a climate change ‘stabilization wedge’. Firstly, evidence of how agricultural soil can serve as a carbon sink in discussed, based on the observed accumulation of inorganic carbon in alkaline mineral-amended soils. Secondly, the impact of alkaline minerals on agricultural soil and crops, and the factors determining the rate of the weathering process are assessed. Lastly, the CO2 sequestration potential via alkaline mineral soil amendment is quantified according to an idealized shrinking core model, which shows that it has the potential to serve as a climate change stabilization wedge.

See full article: Alkaline Mineral Soil Amendment A Climate Stabilization ‘Wedge’.pdf

7.5 Characterization of Physically Fractionated Wollastonite-Amended Agricultural Soils

Wollastonite is a natural silicate mineral that can be used as an agricultural soil amendment. Once in the soil, this mineral undergoes weathering and carbonation reactions, and, under certain soil and field crop conditions, our previous work has shown that this practice leads to accumulation of inorganic carbon (calcium carbonate). Mineral carbonation is the carbon sequestration approach with the greatest potential for sequestration capacity and permanency. Agricultural lands offer vast areas onto which such minerals can be applied, while benefiting crops. This work illustrates a technique to separate wollastonite-containing soils into different fractions. These fractions are characterized separately to determine organic and inorganic content, as well as to determine the chemical and mineral composition. The aim is to detect the fate of wollastonite in agricultural soils, and the fate of weathering/carbonation products in the soil. The soils used in the study were collected from soybean and potato farmlands in Southern Ontario, and from an experimental pilot plot. Soil fractionation was done using sieving, and soil fractions were analyzed by a calcimeter, X-ray diffraction, and loss-on-ignition. Acid digested samples were measured by Inductively Coupled Plasma Mass Spectrometry. Carbonates and wollastonite were enriched by fractionation.

See full article: Characterization of Physically Fractionated Wollastonite-Amended Agricultural Soils.pdf

7.6 The contribution of agricultural lime to carbon dioxide emissions in the United States

Agricultural lime (aglime) is commonly applied to soils in the eastern U.S. to increase soil pH. Aglime includes crushed limestone (CaCO3) and crushed dolomite (MgCa(CO3)2). Following the supposition by the Intergovernmental Panel on Climate Change (IPCC) that all C in aglime is eventually released as CO2 to the atmosphere, the U.S. EPA estimated that 9 Tg (Teragram = 1012 g = 106 metric tonne) CO2 was emitted from an approximate 20 Tg of applied aglime in 2001. A review of historic data on aglime production and use indicates that 30 Tg may better represent the annual U.S. consumption of aglime. More importantly, our review of terrestrial and ocean C dynamics indicates that it is unlikely that all C from aglime is released to the atmosphere following application to soils. On the contrary, the primary pathway for aglime dissolution is reaction with carbonic acid (H2CO3) which results in uptake of CO2. Depending on soil pH and nitrogen fertilizer use, a fraction of aglime may react with strong acid sources such as nitric acid (HNO3), thereby releasing CO2. Data on soil leaching and river transport of calcium (Ca2+) and bicarbonate (HCO3) suggest that a significant portion of dissolved aglime constituents may leach through the soil and be transported by rivers to the ocean. Much of the fraction transported to the ocean will precipitate as CaCO3. Bicarbonate remaining in the soil profile is expected to release CO2 following re-acidification of the soil over time. Our analysis indicates that net CO2 emissions from the application of aglime is 0.059 Mg C per Mg limestone and 0.064 Mg C per Mg dolomite. This is in contrast to IPCC estimates of 0.12 and 0.13 Mg C per Mg limestone and dolomite, respectively. Based on our best estimate, the application of 20–30 Tg of aglime in the U.S., consisting of 80% limestone and 20% dolomite, would have resulted in a net 4.4–6.6 Tg CO2 emissions in 2001.

See full article: The contribution of agricultural lime to carbon dioxide emissions in the United States.pdf

7.7 Potential for large-scale CO2 removal via enhanced rock weathering with croplands

Enhanced silicate rock weathering (ERW), deployable with croplands, has potential use for atmospheric carbon dioxide (CO2) removal (CDR), which is now necessary to mitigate anthropogenic climate change1. ERW also has possible co-benefits for improved food and soil security, and reduced ocean acidification2–4. Here we use an integrated performance modelling approach to make an initial techno-economic assessment for 2050, quantifying how CDR potential and costs vary among nations in relation to business-as-usual energy policies and policies consistent with limiting future warming to 2 degrees Celsius5. China, India, the USA and Brazil have great potential to help achieve average global CDR goals of 0.5 to 2 gigatonnes of carbon dioxide (CO2) per year with extraction costs of approximately US$80–180 per tonne of CO2. These goals and costs are robust, regardless of future energy policies. Deployment within existing croplands offers opportunities to align agriculture and climate policy. However, success will depend upon overcoming political and social inertia to develop regulatory and incentive frameworks. We discuss the challenges and opportunities of ERW deployment, including the potential for excess industrial silicate materials (basalt mine overburden, concrete, and iron and steel slag) to obviate the need for new mining, as well as uncertainties in soil weathering rates and land–ocean transfer of weathered products.

See full article: Potential for large-scale CO2 removal via enhanced rock weathering with croplands.pdf

7.8 Optimizing Inorganic Carbon Sequestration and Crop Yield With Wollastonite Soil Amendment in a Microplot Study

Carbon dioxide (CO2) is a major greenhouse gas, and its concentration in the atmosphere is increasing continuously, hence there is an urgent need to reduce its level in the atmosphere. Soils offer a large natural sink to store CO2. This study focuses on sequestering CO2 in the agricultural soils as inorganic carbon, which can be accomplished by adding alkaline-earth silicates. Wollastonite is used in this study as a soil amendment, to sequester CO2 via the geochemical route of mineral carbonation. The first objective of the present study was to evaluate the effect of mixing a wide range of dosages of wollastonite, as a soil amendment, on the growth performance of two leguminous plants frequently used in agricultural sector: soybean and alfalfa. The plants were grown with different wollastonite dosages (3–20 kg·m−2 for soybean and 3–40 kg·m−2 for alfalfa), for a duration of 14 weeks in a microplot experiment in Ontario, Canada. The second objective was to find evidence of enhanced weathering of wollastonite in soil, in addition to the augmentation of inorganic carbon content in soil. For this, mineralogical assessment of the soils was performed using XRD and SEM-EDS analyses. Wollastonite increased the soybean yield by two-fold in the plot amended with 10 kg·m−2. At all dosages, wollastonite increased the alfalfa growth in terms of height and above-ground biomass dry weight, as well as root biomass. The rate of CO2 sequestration, at optimum wollastonite dosage, reached 0.08 kg CO2·m−2·month−1. XRD and SEM-EDS analyses indicated accumulation of calcite in wollastonite-amended soil and formation of other weathering products. The results obtained from this study help to understand the impact of wollastonite soil amendment on agronomy, and will aid in implementing such negative emissions technology by informing farmers and industry alike that the use of wollastonite contributes toward global climate change mitigation while supporting crop yield. The findings of this study add to the existing body of knowledge on enhanced weathering as an atmospheric CO2 removal technology, providing further evidence that wollastonite weathering in agricultural soils can lead to significant capacity for CO2 sequestration as inorganic carbon, while concurrently promoting plant growth.

See full article: Optimizing Inorganic Carbon Sequestration and Crop Yield With Wollastonite Soil Amendment in a Microplot Study.pdf

7.9 Calcium-mediated stabilisation of soil organic carbon

Soils play an essential role in the global cycling of carbon and understanding the stabilisation mechanisms behind the preservation of soil organic carbon (SOC) pools is of globally recognised significance. Until recently, research into SOC stabilisation has predominantly focused on acidic soil environments and the interactions between SOC and aluminium (Al) or iron (Fe). The interactions between SOC and calcium (Ca) have typically received less attention, with fewer studies conducted in alkaline soils. Although it has widely been established that exchangeable Ca (CaExch) positively correlates with SOC concentration and its resistance to oxidation, the exact mechanisms behind this relationship remain largely unidentified. This synthesis paper critically assesses available evidence on the potential role of Ca in the stabilisation of SOC and identifies research topics that warrant further investigation. Contrary to the common view of the chemistry of base cations in soils, chemical modelling indicates that Ca2? can readily exchange its hydration shell and create inner sphere complexes with organic functional groups. This review therefore argues that both inner- and outer-sphere bridging by Ca2? can play an active role in the stabilisation of SOC. Calcium carbonate (CaCO3) can influence occluded SOC stability through its role in the stabilisation of aggregates; however, it could also play an unaccounted role in the direct sorption and inclusion of SOC. Finally, this review highlights the importance of pH as a potential predictor of SOC stabilisation mechanisms mediated by Al- or Fe- to Ca, and their respective effects on SOC dynamics.

See full article: Calcium-mediated stabilisation of soil organic carbon.pdf

 

7.10 Assessment of the enhanced weathering potential of different silicate minerals to improve soil quality and sequester CO2

Abstract:

Enhanced weathering is a negative emission technology that involves the spread of crushed silicate minerals and rocks on land and water. When applied to agricultural soils, the resulting increase in soil pH and release of nutrients may co-benefit plant productivity. Silicate minerals and rocks differ in their enhanced weathering potential, i.e., their potential for both carbon dioxide (CO₂) sequestration and soil quality improvements. However, studies comparing silicate minerals and rocks for this dual potential are lacking. Therefore, we compared the enhanced weathering potential of olivine (Mg₂SiO₄), basalt, wollastonite (CaSiO₃), and two minerals that are novel in this context, anorthite (CaAl₂Si₂O₈) and albite (NaAlSi₃O₈). A down-flow soil column experiment was designed allowing for measurements on soils and leachate, and calculations of organic and inorganic carbon budgets. Our results showed comparatively high CO₂ capture by enhanced wollastonite and olivine weathering. Furthermore, CO₂ capture per m²specific surface area indicated potential for enhanced anorthite and albite weathering. Calculated carbon budgets showed that most treatments produced net CO₂ emissions from soils, likely related to the short duration of this experiment. All silicates generally improved soil quality, with soil nickel contents remaining below contamination limits. However, nickel concentrations in leachates from olivine-amended soils exceeded the groundwater threshold value, stressing the importance of monitoring nickel leaching. We found a relatively high enhanced weathering potential for wollastonite, while the potential for olivine may be constrained by nickel leaching. The promising results for anorthite and albite indicate the need to further quantify their enhanced weathering potential.

See full article: Assessment of the enhanced weathering potential of different silicate minerals.pdf

See our blog on this study

7.11 Mineral–Soil–Plant–Nutrient Synergisms of Enhanced Weathering for Agriculture: Short-Term Investigations Using Fast-Weathering Wollastonite Skarn

Enhanced weathering is a proposed carbon dioxide removal (CDR) strategy to accelerate natural carbon sequestration in soils via the amendment of silicate rocks to agricultural soils. Among the suitable silicates (such as basalt and olivine), the fast-weathering mineral wollastonite (CaSiO3) stands out. Not only does the use of wollastonite lead to rapid pedogenic carbonate formation in soils, it can be readily detected for verification of carbon sequestration, but its weathering within weeks to months influences soil chemistry and plant growth within the same crop cycle of its application. This enables a variety of short-term experimental agronomic studies to be conducted to demonstrate in an accelerated manner what could take years to be observed with more abundant but slower weathering silicates. This study presents the results of three studies that were conducted to investigate three distinct aspects of wollastonite skarn weathering in soils in the context of both agricultural and horticultural plants. The first study investigated the effect of a wide range of wollastonite skarn dosages in soil (1.5–10 wt.%) on the growth of green beans. The second study provides insights on the role of silicon (Si) release during silicate weathering on plant growth (soybeans and lettuce). The third study investigated the effect of wollastonite skarn on the growth of spring rye when added to soil alongside a nitrogen-based coated fertilizer. The results of these three studies provide further evidence that amending soil with crushed silicate rocks leads to climate-smart farming, resulting in inorganic carbon sequestration, as well as better plant growth in agricultural (soybean and spring rye) and horticultural (green bean and lettuce) crops. They also demonstrate the value of working with wollastonite skarn as a fast-weathering silicate rock to accelerate our understanding of the mineral–soil–plant–nutrient synergism of enhanced weathering.Enhanced weathering is a proposed carbon dioxide removal (CDR) strategy to accelerate natural carbon sequestration in soils via the amendment of silicate rocks to agricultural soils. Among the suitable silicates (such as basalt and olivine), the fast-weathering mineral wollastonite (CaSiO3) stands out. Not only does the use of wollastonite lead to rapid pedogenic carbonate formation in soils, it can be readily detected for verification of carbon sequestration, but its weathering within weeks to months influences soil chemistry and plant growth within the same crop cycle of its application. This enables a variety of short-term experimental agronomic studies to be conducted to demonstrate in an accelerated manner what could take years to be observed with more abundant but slower weathering silicates. This study presents the results of three studies that were conducted to investigate three distinct aspects of wollastonite skarn weathering in soils in the context of both agricultural and horticultural plants. The first study investigated the effect of a wide range of wollastonite skarn dosages in soil (1.5–10 wt.%) on the growth of green beans. The second study provides insights on the role of silicon (Si) release during silicate weathering on plant growth (soybeans and lettuce). The third study investigated the effect of wollastonite skarn on the growth of spring rye when added to soil alongside a nitrogen-based coated fertilizer. The results of these three studies provide further evidence that amending soil with crushed silicate rocks leads to climate-smart farming, resulting in inorganic carbon sequestration, as well as better plant growth in agricultural (soybean and spring rye) and horticultural (green bean and lettuce) crops. They also demonstrate the value of working with wollastonite skarn as a fast-weathering silicate rock to accelerate our understanding of the mineral–soil–plant–nutrient synergism of enhanced weathering.

Read the full study here: Mineral–Soil–Plant–Nutrient Synergisms of Enhanced Weathering for Agriculture: Short-Term Investigations Using Fast-Weathering Wollastonite Skarn.pdf 

8. Environmental Stress Tolerance

8.1 Functions of silicon in plant drought stress responses

Silicon (Si), the second most abundant element in Earth’s crust, exerts beneficial effects on the growth and productivity of a variety of plant species under various environmental conditions. However, the benefits of Si and its importance to plants are controversial due to differences among the species, genotypes, and the environmental conditions. Although Si has been widely reported to alleviate plant drought stress in both the Si-accumulating and non accumulating plants, the underlying mechanisms through which Si improves plant water status and maintains water balance remain unclear. The aim of this review is to summarize the morphoanatomical, physiological, biochemical, and molecular processes that are involved in plant water status that are regulated by Si in response to drought stress, especially the integrated modulation of Si-triggered drought stress responses in Si accumulators and intermediate- and excluder-type plants. The key mechanisms influencing the ability of Si to mitigate the effects of drought stress include enhancing water uptake and transport, regulating stomatal behavior and transpirational water loss, accumulating solutes and osmoregulatory substances, and inducing plant defense-associated with signaling events, consequently maintaining whole-plant water balance. This study evaluates the ability of Si to maintain water balance under drought stress conditions and suggests future research that is needed to implement the use of Si in agriculture. Considering the complex relationships between Si and different plant species, genotypes, and the environment, detailed studies are needed to understand the interactions between Si and plant responses under stress conditions.

See full article: Functions of silicon in plant drought stress responses.pdf

8.2 Calcium Addition At The Hubbard Brook Experimental Forest Increases Sugar Storage, Antioxidant Activity And Cold Tolerance In Native Red Spruce

Summary In fall (November 2005) and winter (February 2006), we collected current-year foliage of native red spruce (Picea rubens Sarg.) growing in a reference watershed and in a watershed treated in 1999 with wollastonite (CaSiO3, a slow-release calcium source) to simulate preindustrial soil calcium concentrations (Ca-addition watershed) at the Hubbard Brook Experimental Forest (Thornton, NH). We analyzed nutrition, soluble sugar concentrations, ascorbate peroxidase (APX) activity and cold tolerance, to evaluate the basis of recent (2003) differences between watersheds in red spruce foliar winter injury. Foliar Ca and total sugar concentrations were significantly higher in trees in the Ca-addition watershed than in trees in the reference watershed during both fall (P = 0.037 and 0.035, respectively) and winter (P = 0.055 and 0.036, respectively). The Ca-addition treatment significantly increased foliar fructose and glucose concentrations in November (P = 0.013 and 0.007, respectively) and foliar sucrose concentrations in winter (P = 0.040). Foliar APX activity was similar in trees in both watersheds during fall (P = 0.28), but higher in trees in the Ca-addition watershed during winter (P = 0.063). Cold tolerance of foliage was significantly greater in trees in the Ca-addition watershed than in trees in the reference watershed (P < 0.001). Our results suggest that low foliar sugar concentrations and APX activity, and reduced cold tolerance in trees in the reference watershed contributed to their high vulnerability to winter injury in 2003. Because the reference watershed reflects forest conditions in the region, the consequences of impaired physiological function caused by soil Ca depletion may have widespread implications for forest health.

See full article: Calcium addition increases sugar storage, antioxidant activity and cold tolerance in native red spruce (Picea rubens).pdf

8.3 Effects of Silicon on Growth, Yield and Fruit Quality of Cantaloupe under Drought Stress

Read more: Effects of Silicon on Growth, Yield and Fruit Quality of Silicon on Cantaloupe

 

9. Silicon Cycling

9.1 Silicon Cycling in Soils Revisited – 2021