Plant-available Si Research Articles

Silica Accumulation in Potato (Solanum tuberosum L.) Plants and Implications for Potato Yield Performance-Results from Field Experiments in Northeast Germany.

The potato is the most important non-cereal food crop, and thus improving potato growth and yield is the focus of agricultural researchers and practitioners worldwide. Several studies reported beneficial effects of silicon (Si) fertilization on potato performance, although plant species from the family Solanaceae are generally considered to be non-Si-accumulating. We used results from two field experiments in the temperate zone to gain insight into silica accumulation in potato plants, as well as corresponding long-term potato yield performance. We found relatively low Si contents in potato leaves and roots (up to 0.08% and 0.3% in the dry mass, respectively) and negligible Si contents in potato tuber skin and tuber flesh for plants grown in soils with different concentrations of plant-available Si (field experiment 1). Moreover, potato yield was not correlated to plant-available Si concentrations in soils in the long term (1965-2015, field experiment 2). Based on our results, we ascribe the beneficial effects of Si fertilization on potato growth and yield performance reported in previous studies mainly to antifungal/osmotic effects of foliar-applied Si fertilizers and to changes in physicochemical soil properties (e.g., enhanced phosphorus availability and water-holding capacity) caused by soil-applied Si fertilizers.

Impact of earthworms on soil Si availability and wheat Si concentration in low- and high-Si soils

Silicon (Si) is a beneficial element known to increase growth and the stress resistance of plants, including resistance against drought. However, as with many other elements, only a small fraction of Si in soils is available for plant uptake. Plant-available Si originates either from the weathering of soil minerals or from the dissolution of phytoliths in plant litter. It is known that soil fauna plays a role in both processes that contribute to the availability of Si in the soil. However, very little is known about the interactions between the weathering of soil minerals and the dissolution of Si by earthworms from phytoliths and subsequent Si uptake by plants. In greenhouse pot experiments, this study investigated the effect of an epigeic earthworm species (Dendrobaena veneta) on Si availability and uptake by wheat (Triticum aestivum) grown in soils with high or low Si availability. In addition, Si-rich plant litter (wheat straw) was added to the topsoil in some treatments. The addition of plant litter significantly increased the available Si in the soil. Plant litter addition was positively correlated with the Si concentration in wheat in low-Si soil, but not in high-Si soil. Earthworms increased Si availability in soil and casts of the low-Si soil and partly of the high-Si soil, but not Si uptake by wheat. These results suggest that earthworms play an important role in regulating the Si status of soils and may influence Si uptake by plants, especially in soils with initially low Si content and when earthworm population densities are high.

Silicon in paddy fields: Benefits for rice production and the potential of rice phytoliths for biogeochemical carbon sequestration

Silicon (Si) biogeochemical cycling is beneficial for crop productivity and carbon (C) sequestration in agricultural ecosystem, thus offering a nonnegligible role in alleviating global warming and food crisis. Compared with other crops, rice plants have a greater quantity of phytolith production, because they are able to take up a lot of Si. However, it remains unclear on Si supply capacity of paddy soils across the world, general rice yield-increasing effect after Si fertilizer addition, and factors affecting phytolith production and potential of phytolith C sequestration in paddy fields. This study used a meta-analysis of >3500 data from 87 studies to investigate Si supply capacity of global paddy soils and elaborate the benefits of Si regarding rice productivity and phytolith C sequestration in paddy fields. Analytical results showed that the Si supply capacity of paddy soils was insufficient in the major rice producing countries/regions. Dealing with this predicament, Si fertilization was an effective strategy to supply plant-available Si to improve rice productivity. Our meta-analysis results further revealed that Si fertilization led to the average increasing rate of 36 % and 39 % in rice yield and biomass, which could reach up to 52 % and 46 % with the increasing doses of Si fertilizer, respectively. Especially, this strategy also improved the potential of phytolith C sequestration through the increased phytolith content and rice biomass, despite that this potential might have a decline in old paddy soils (≥ 7000 year) compared to in young paddy soils (≤ 1000 year) due to the slow migration and dissolution of phytoliths at millennial scale. Our findings thus indicate that a deep investigation on the benefits of Si in agroecosystem will further improve our understanding on regulating crop production and the potential of biogeochemical C sequestration within phytoliths in global cropland.

Earthworms impact the availability of Si to plants in northern Vietnamese paddy fields

Silicon (Si) is an essential element for the growth and development of rice plants, playing a crucial role in their overall health and productivity. This study aimed to measure earthworm's impact on Si dynamics in northern Vietnam's paddy fields. The properties of earthworm casts from 23 different sites were compared to the surrounding topsoil. The results showed that the casts were enriched in biogenic silica (herein phytoliths) and plant-available Si (measured through acid acetic extraction, SiAC) compared to the reference topsoil. Also, casts had a higher sand content, while their carbon content was similar to the reference soils. This suggests a possible preference for sand particles by earthworms (e.g., for grinding plant material within their gizzards) and/or the consumption of soil from another layer enriched in sand content. The influence of earthworms on Si dynamics was found to be dependent on the soil's environmental properties. In soils with low fertility (characterized by a higher proportion of sand and lower concentrations of C and oxides), earthworms increased the concentration of SiAC. However, beyond a certain level, the effect of earthworms on Si availability became neutral. While this study highlights the critical role of earthworms in paddy fields, further research is needed to understand how earthworms enhance the concentration in SiAC in the topsoil, and the consequences to rice growth and resistance to environmental hazards.

Effects of turning rainforest into oil-palm plantations on silicon pools in soils within the first 20 years after the transformation

Potential effects of land-use/land-cover (LULC) transformation from lowland rainforest into oil-palm plantations on silicon (Si) pools in tropical soils remain poorly understood, although appropriate levels of plant-available Si in soils may contribute to maintain high crop yields and increase the vitality and drought resistance of oil palms. Therefore, the aim of our study was to identify possible effects of such LULC change on soil Si pools. For this purpose, we compared soil Si pools under lowland rainforest and ca. 20 year-old oil-palm plantations in Jambi Province, Indonesia. The investigated soils were Acrisols and Stagnosols, in which we quantified six different soil Si pools following a sequential extraction procedure to evaluate, whether 20 years of oil-palm cultivation has led to a depletion of these soil Si pools. The considered pools included mobile Si, adsorbed Si, Si bound in soil organic matter (SOM), Si included in pedogenic oxides and hydroxides, and Si in amorphous silica of biogenic and pedogenic origin. Finally, we also determined total Si. All oil-palm plantations established on sloping terrain and Acrisols only showed decreased Si stocks of mobile Si, adsorbed Si and SOM-bound Si; those established in floodplains and Stagnosols had decreased stocks of SOM-bound Si and biogenic-amorphous silica. Lower Si stocks were mostly attributed to a missing “stable” phytolith pool in the subsoil and less organic matter in topsoils under oil-palm plantations. When comparing well-drained and riparian areas, flooding seemed to increase phytolith dissolution. We conclude that 20 years of oil-palm cultivation has not yet led to a significant depletion of soil Si pools. As topsoils comprise the highest concentrations of SOM-bound Si and Si in amorphous silica of biogenic origin but are susceptible to erosion and surface runoff under managed oil-palm plantations, it would be advisable to instate specific management practices that maintain organic-rich and well-aired topsoils on oil-palm plantations.

Estimating oil-palm Si storage, Si return to soils, and Si losses through harvest in smallholder oil-palm plantations of Sumatra, Indonesia

Abstract. Most plant-available Si in strongly desilicated soils is provided through litter decomposition and subsequent phytolith dissolution. The importance of silicon (Si) cycling in tropical soil–plant systems raised the question of whether oil-palm (Elaeis guineensis Jacq.) cultivation alters Si cycling. As oil palms are considered Si hyper-accumulators, we hypothesized that much Si is stored in the above-ground biomass of oil palms with time. Furthermore, the system might lose considerable amounts of Si every year through fruit-bunch harvest. To test these hypotheses, we analysed Si concentrations in fruit-bunch stalks, fruit pulp and kernels, leaflets, rachises, and frond bases of mature oil palms on eight smallholder oil-palm plantations in Sumatra, Indonesia. We estimated Si storage in the total above-ground biomass of oil palms, Si return to soils through decomposing pruned palm fronds, and Si losses from the system through harvest. Leaflets of oil-palm fronds had a mean Si concentration of > 1 wt %. All other analysed plant parts had < 0.5 wt % Si. According to our estimates, a single palm tree stored about 4–5 kg Si in its total above-ground biomass. A smallholder oil-palm plantation stored at least 550 kg Si ha−1 in the palm trees' above-ground biomass. Pruned palm fronds returned 111–131 kg of Si ha−1 to topsoils each year. Fruit-bunch harvest corresponded to an annual Si export of 32–72 kg Si ha−1 in 2015 and 2018. Greater Si losses (of at least 550 kg Si ha−1) would occur from the system if oil-palm stems were removed from plantations prior to replanting. Therefore, it is advisable to leave oil-palm stems on the plantations, e.g. by distributing chipped stem parts across the plantation at the end of a plantation cycle (∼ 25 years).

Silicon modification improves biochar’s ability to mitigate cadmium toxicity in tomato by enhancing root colonization of plant-beneficial bacteria

Modification of biochar, such as impregnation with minerals, can improve biochar’s efficacy to mitigate heavy metal toxicity in plants. Biochar amendments can alter plant rhizosphere microbiome, which has profound effects on plant growth and fitness. Here, we tested whether rhizosphere microbiome is involved in the ability of silicon (Si)-modified biochar to mitigate cadmium toxicity in tomato (Solanum lycopersicum L.). We demonstrated that Si modification altered biochar’s physico-chemical properties and enhanced its ability to mitigate cadmium toxicity in tomato. Particularly, the Si-modified biochar contained higher content of Si and increased plant-available Si content in the soil. The rhizosphere microbiome transplant experiment showed that changes in rhizosphere microbiome contributed to the mitigation of cadmium toxicity by biochar amendments. The raw biochar and Si-modified biochar differently altered tomato rhizosphere bacterial community composition. Both biochars, especially the Si-modified biochar, promoted specific bacterial taxa (e.g., Sphingomonas, Lysobacter and Pseudomonas spp.). Subsequent culturing found these promoted bacteria could mitigate cadmium toxicity in tomato. Moreover, both biochars stimulated tomato to recruit plant-beneficial bacteria with Si-modified biochar having stronger stimulatory effects, indicating that the positive effects of biochar on plant-beneficial bacteria was partially mediated via the host plant. Overall, Si modification enhanced biochar’s ability to mitigate cadmium toxicity, which was linked to the stimulatory effects on plant-beneficial bacteria.

Citrate-modified biochar for simultaneous and efficient plant-available silicon release and copper adsorption: Performance and mechanisms

Silicon (Si) deficiency and heavy metals (HMs) pollution are common for farmland soil because of long-term intensive farming. In this study, a novel citrate-modified biochar (C-BC) was introduced as a soil conditioner to simultaneously increase the amount of plant-available Si (PASi) and immobilize HMs. The maximum amount of PASi released was 33.00 mg⋅g−1 from C-BC pre-treated with 0.1 mol⋅L−1 citrate (C-BC0.1). A formation–transport coupling mechanism for increasing the amount of PASi released was developed. Stable Si in the biomass was pyrolyzed to give silicate that was relatively mobile via nucleophilic attack of citrate and hydrolysis of amorphous Si. Silicate species were then released through the porous surface and widening cracks caused by pyrolysis. At citrate concentrations >0.1 mol⋅L−1, the surface and cracks were easily blocked by precipitates formed during pyrolysis. The ability of C-BC to remove HMs was assessed using Cu as an example. C-BC0.1 was optimal for adsorbing Cu, and the maximum adsorption capacity was 271.73 mg⋅g−1. The Cu adsorption mechanism mainly involved surface precipitation, surface complexation, electrostatic attraction and hydrogen bonding. Our research provides important implications for simultaneously addressing Si deficiency and HMs contaminant problems by these materials for soil amendment in agro-ecosystem.

Spatial distribution of plant-available silicon and its controlling factors in paddy fields of China

Silicon (Si) is beneficial for rice health and production by alleviating various biotic and abiotic stresses. However, the continual export of grain off-farm may result in Si deficiency for rice plants. The current levels of plant available Si (PASi) in rice paddies in China remain unclear, as do the factors that control PASi content in these soils. We conducted a nationwide sampling campaign across the paddy fields of China between 2016 and 2019, and used calcium chloride extractable Si (Si-CaCl2) and buffered acetate extractable Si (Si-NaAc, pH = 4) to quantify PASi. We show that Si-CaCl2 pool was mainly influenced by mean annual temperature (MAT), soil salinity, soil organic carbon (SOC), mean annual precipitation (MAP), and soil pH, suggesting both pedological and biological control mechanisms. However, the Si-NaAc pool was influenced most by soil pH, MAT and MAP, implying pedological control. Compared to data from the 1990s, the Si-NaAc content decreased by 14.1% on a national scale with an annual decline rate of 0.54%. Based on our investigation, at least 65% of China’s paddy fields are deficient in PASi, which is an increase in area of ~15% over the last 20 years. The principal regions where PASi deficiency was recorded are mainly located in southern China, with the levels of Si deficiency lowering as the paddy fields are located further north. The continual off-site removal of PASi from rice grain and straw will need to be addressed through the use of Si-fertilizers, including organic amendments, to maintain a productive and sustainable rice industry in China.

Silicon uptake and isotope fractionation dynamics by crop species

Abstract. That silicon is an important element in global biogeochemical cycles is widely recognised. Recently, its relevance for global crop production has gained increasing attention in light of possible deficits in plant-available Si in soil. Silicon is beneficial for plant growth and is taken up in considerable amounts by crops like rice or wheat. However, plants differ in the way they take up silicic acid from soil solution, with some species rejecting silicic acid while others actively incorporate it. Yet because the processes governing Si uptake and regulation are not fully understood, these classifications are subject to intense debate. To gain a new perspective on the processes involved, we investigated the dependence of silicon stable isotope fractionation on silicon uptake strategy, transpiration, water use, and Si transfer efficiency. Crop plants with rejective (tomato, Solanum lycopersicum, and mustard, Sinapis alba) and active (spring wheat, Triticum aestivum) Si uptake were hydroponically grown for 6 weeks. Using inductively coupled plasma mass spectrometry, the silicon concentration and isotopic composition of the nutrient solution, the roots, and the shoots were determined. We found that measured Si uptake does not correlate with the amount of transpired water and is thus distinct from Si incorporation expected for unspecific passive uptake. We interpret this lack of correlation to indicate a highly selective Si uptake mechanism. All three species preferentially incorporated light 28Si, with a fractionation factor 1000×ln (α) of −0.33 ‰ (tomato), −0.55 ‰ (mustard), and −0.43 ‰ (wheat) between growth medium and bulk plant. Thus, even though the rates of active and passive Si root uptake differ, the physico-chemical processes governing Si uptake and stable isotope fractionation do not. We suggest that isotope fractionation during root uptake is governed by a diffusion process. In contrast, the transport of silicic acid from the roots to the shoots depends on the amount of silicon previously precipitated in the roots and the presence of active transporters in the root endodermis, facilitating Si transport into the shoots. Plants with significant biogenic silica precipitation in roots (mustard and wheat) preferentially transport silicon depleted in 28Si into their shoots. If biogenic silica is not precipitated in the roots, Si transport is dominated by a diffusion process, and hence light silicon 28Si is preferentially transported into the tomato shoots. This stable Si isotope fingerprinting of the processes that transfer biogenic silica between the roots and shoots has the potential to track Si availability and recycling in soils and to provide a monitor for efficient use of plant-available Si in agricultural production.

Agriculture increases the bioavailability of silicon, a beneficial element for crop, in temperate soils

Crops may take benefits from silicon (Si) uptake in soil. Plant available Si (PAS) can be affected by natural weathering processes or by anthropogenic forces such as agriculture. The soil parameters that control the pool of PAS are still poorly documented, particularly in temperate climates. In this study, we documented PAS in France, based on statistical analysis of Si extracted by CaCl2 (SiCaCl2) and topsoil characteristics from an extensive dataset. We showed that cultivation increased SiCaCl2 for soils developed on sediments, that cover 73% of France. This increase is due to liming for non-carbonated soils on sediments that are slightly acidic to acidic when non-cultivated. The analysis performed on non-cultivated soils confirmed that SiCaCl2 increased with the < 2 µm fraction and pH but only for soils with a < 2 µm fraction ranging from 50 to 325 g kg−1. This increase may be explained by the < 2 µm fraction mineralogy, i.e. nature of the clay minerals and iron oxide content. Finally, we suggest that 4% of French soils used for wheat cultivation could be deficient in SiCaCl2.

Enhanced solubilization of insoluble silicate from quartz and zeolite minerals by selected Aspergillus and Trichoderma species

Silicon (Si) is a major component of sand, silt and clay particles of soils. Available silica as silicic acid (H4SiO4) present in soil solution is considerably low, only in the range of 3.5–40.0 mg Si L-1. To improve plant-available Si in the soil, silicate-solubilizing fungi (SSF) are potentially important in solubilizing insoluble forms of silicate (SiO2). The objectives of this study were to determine silicate solubilizing capacity and organic acid produced by seven SSF isolates on Bunt and Rovira media by using 0.25% (w/v) magnesium trisilicate (Mg2O8Si3), quartz, and zeolite as a silica source. Determination of SSF isolates potential in Si solubilization was carried out in a completely randomized design with three silica sources and three replicates. The results indicated that all SSF were capable of producing acetic, citrate, and oxalic acids and enhancing the solubilization of insoluble silicates. Trichoderma polysporum and Aspergillus niger BCCF194 were the best isolates of SSF. Furthermore, there was significantly (p&lt;0.05) positive correlation between solubilizing silicate capacity by using quartz or zeolite as a silica source on Bunt and Rovira media with incubation time (R2 = 0.79-0.99) and citric acid production (R2= 0.97-0.99) from T. polysporum and A. niger BCCF194

Regulation of As and Cd accumulation in rice by simultaneous application of lime or gypsum with Si-rich materials.

Calcium (Ca) and silicon (Si) have been found to reduce inorganic pollutant accumulation by agricultural plants. Arsenic (As) and cadmium (Cd) are the most common and dangerous inorganic pollutants in cultivated soil that often present simultaneously. Due to difference in chemical properties of As and Cd, concurrent minimizing their uptake poses a problem. The effect of two types of Si fertilizers and Si-treated metallurgical slag applied with or without limestone or gypsum on the As and Cd accumulation by rice was investigated in medium-polluted paddy soils in field test. Application of Ca- and Si-rich substances reduced the grain As by 16 to 68% and the grain Cd by 30 to 56% with increasing yield by 16.6 to 31.0%. The root-to-grain transport of As and Cd depended on the plant-available Si supply in the soil. Soil-applied Si resulted in diminished As and Cd translocation inside plant tissue and decreased the pollutant mobility in the soil. The combination of Ca- and Si-rich substances reinforced the reduction in both the pollutant mobility in soil and accumulation by rice grain. Silicon-rich materials mainly impacted both As and Cd translocation into the grain, whereas Ca-rich substances demonstrated a more remarkable effect on the pollutant mobility in the soil. Limestone showed a higher decrease in the mobility of Cd, while gypsum was more efficient in the case of As. Thus, for minimizing pollutant accumulation by rice grain, the combination of Si fertilizer with limestone or gypsum could be recommended in the co-contaminated soil with prevailing Cd or As, respectively.

Effects of silicon amendments on grapevine, soil and wine

Replacing Bordeaux broth and synthetic fungicides by less invasive approaches of fungal disease control remains a challenge for both conventional and organic viticulture. Silicon (Si) application has been proposed as a viable alternative for the control of pathogens and other stresses in agriculture. In a three-year field trial, we tested the effect of foliar and soil application of colloidal silicon on its availability in vineyard soil and pants, the performance and quality of yield, and finally, the control of powdery mildew for grapevine cv. Grüner Veltliner. Soil application of colloidal silicon increased plant-available Si, but only foliar application increased the total silicon concentrations in leaves, yield, and cluster weight. Moreover, the wine produced from the silica-treated grapes were ranked better in sensory evaluations. Our findings provide evidence for the potential of at least partially replacing conventional fungicides, rendering viticulture more sustainable in terms of soil protection and biodiversity. Silicon applications are low in costs and comply with the principles of organic wine production.

Silicon recycling through rice residue management does not prevent silicon depletion in paddy rice cultivation

Silicon (Si) is known to help plants mitigate environmental stresses and nutrient deficits. In some regions, the limited plant-available Si in soils can have detrimental effects on yields. Crop residue recycling is used to maintain the amount of plant-available Si in soils. However, the effect of crop residue management practices on Si availability to plants remains largely understudied. Here, we study the effects of three different rice residue management practices on Si-depleted rice fields in northern Vietnam. These management practices were (1) the direct incorporation of rice residues into soils, (2) burning in the field, and (3) use as fodder for animals, followed by composting of the obtained manure, and subsequent application to the field. We analyzed different Si reservoirs in soils and the content of plant-Si under these different practices. Our results show correlations between plant Si content and the different soil Si reservoirs, in particular with Si trapped in soil organic material (SiOrg; R2 = 0.68, n = 18, p < 10–4). However, we found no significant difference between the three residue management practices with respect to plant-available Si in soils and to the content of plant-Si. Moreover, our data suggest that strongly Si-depleted rice-cultivation systems proportionally lose Si through grain harvesting twice as fast as less Si-depleted systems because of the enhanced relative Si accumulation in grain. This loss cannot be mitigated by the recycling of rice residues, which suggests that the recycling of rice residues has only a limited effect in extremely Si-depleted rice-cultivation systems.

Effect of Crop Rotations and Continuous Fertilization on the Status of Silicon (Si) Available in Soil in a 97-Year Permanent Experiment

ABSTRACT This work aims to study the status of silicon (Si) as a plant nutrient in the soil of Bahtim long-term field experiment in Egypt under the effect of crop rotations system and continuous fertilization. The experiment has been set up since 1912 based on two main factors: (1) crop rotations: mono-cropping (MC), two-year rotation (2Y-R), and three-year rotation (3Y-R), and (2) Fertilization: mineral nitrogen N, phosphorus P, potassium K, and organic farmyard manure FYM. Available N, P, K, and Si in soil were estimated. Productivity of soil was evaluated using Berseem (Trifolium alexndrinum L.) cultivated and harvested in 2019. The plant-available Si (PAS) in soil decreased significantly compared to the control C in case of MC by 70.26%, 2Y-R by 85.09%, and 3Y-R by 92.65% in the direction of N > NP > NPK. Mineral fertilization decreased the PAS significantly by 12.84% N, 29.52% NP, 78.45% NPK compared to the control C in the order of MC > 2Y-R > 3Y-R. Berseem yield (t ha−1) increased significantly compared with the control C following the order C < N < NP < NPK. The most significant increase in the yield was recorded for the NPK treatments by 224.04%, and 200% in case of MC, 2Y-R, 3Y-R, respectively.

Exogenous Application of Different Silicon Sources and Potassium Reduces Pink Stem Borer Damage and Improves Photosynthesis, Yield and Related Parameters in Wheat

Silicon (Si) and potassium are known to impart tolerance against numerous biotic stresses in crop plants. A study was conducted to determine the effect of diatomaceous earth (DE), a soil-applied Si source and soluble silicic acid, a foliar applied Si source at two levels of potassium for their efficacy against pink stem borer (PSB) incidence and damage in wheat under field conditions for two seasons. The effect of these Si sources and potassium levels on photosynthesis, yield, and related parameters were also studied. Soil application of DE @ 300 kg ha−1 significantly decreased the PSB incidence with the lowest percent white ear damage and recorded the highest grain yield of 3.31 t ha−1. Both soil and foliar applied Si sources along with potassium @ 36 kg ha−1 significantly enhanced the net photosynthesis rate, stomatal conductance, water use efficiency, intercellular CO2 concentration, spike length, spike weight, number of grains per spike, 1000 grains weight and significantly decreased the transpiration rate in contrast to untreated control (no Si application) and insecticidal check. Soil applied Si sources significantly enhanced plant-available Si content in soil solution and thereby Si content in stem tissues of wheat plants in contrast to foliar-applied Si sources. Maximum Benefit: Cost ratio (2.03) was recorded with soil application of DE @ 150 kg ha−1 which was more than recommended insecticidal check (1.74). Both Si sources proved significantly superior to insecticidal check in managing PSB in wheat under field conditions and improved photosynthesis, yield and related parameters, which can be integrated with other practices for sustainable, eco-friendly management of PSB in wheat.

Effect of biochars, biogenic, and inorganic amendments on dissolution and kinetic release of phytoavailable silicon in texturally different soils under submerged conditions

Extensive cropping leads to higher removal of silicon (Si) from the soils and makes it a limiting element for various crops. Application of silicic acid (H4SiO4) has limited scope due to high cost, low solubility, and high polymerization. The biogenic sources of Si are alternative to silicic acid (H4SiO4) and Si release from these sources is a function of different soil properties like pH, redox potential, texture etc. Kinetics release of plant available Si (PASi) from various organic and inorganic sources was evaluated in texturally different soils such as sandy loam (SL), sandy clay loam (SCL), and clay (CL) under a 60-day incubation study. Our findings suggest that the highest cumulative release of Si (cSi) was observed in SCL (47.6 mg/L) in control sets without any amendments. The highest cSi release among plant residue amendments was observed by bamboo leaves (340 mg/L) and rice husk (RH) (301 mg/L) in SL and SCL soils, respectively. Among biochar amendments, the rice husk biochar (RHB) released the maximum quantity (246.55 and 243.9 mg/L) of Si in SCL and CL soils respectively. Among the ashes, sugarcane bagasse ash had the highest release (316 mg/L) of Si in SCL and RHA which yielded 235.2 Si mg/L in CL soil for 60days. Silicon release kinetics for these sets of systems showed a diffusive behavior of Si being released from amendments primarily dependent on soil type.

Agronomic Efficiency of Feldspar, Quartz Silica, and Zeolite as Silicon (Si) Fertilizers in Sandy Soil

ABSTRACT Partial replacement of synthetic chemical fertilizers by naturally occurring alternatives is environmentally recommended. Feldspars (F), quartz silica (S), and zeolites (Z) are silicon (Si)-rich minerals that may be utilized as Si fertilizers. This study aims to assess the agronomic efficiency (AE) of the mentioned minerals as Si fertilizers and to estimate Si-use efficiency (Si-UE) in sandy soil. A field experiment was carried out (summer seasons of 2016 and 2017) in which F, S, and Z were mixed with surface soil in an application rate 500 mg kg−1 soil with and without potassium humate (K-H, 2 mg kg−1 soil). Treatments were distributed in a complete randomized block design (CRBD) with three replicates including control before cultivation of soybean (Glycine max L.). Yield (kg ha−1) of soybean, available Si (mg kg−1) in soil and uptake (mg kg−1) of N, P, K, Cu, Fe, Mn, Zn, and Si by soybean seeds and straw were estimated. The most significant increase was by 67.87% followed by 38.69% was recorded for the S and S K-H treatments, compared to the control. Same treatments showed nonsignificant decrease in the available Si (mg kg−1) that may refer to partial replenishment of plant available Si (PAS) in soil and avoid significant deficiency. Silica treatments resulted in the most significant increase in the uptake (mg kg−1 soil) of Si, N, P, K, Cu, Fe, Mn, and Zn by seeds and almost by straw. Silica was more efficient agronomically than feldspar and zeolite. Absorption of more biocompatible Si-organo species may depend on Si source.

Silicon (Si) use efficiency in sandy soil amended by Si-loaded hydrogel

ABSTRACTSilicon (Si) plays an essential role in the mineral nutrition of plants. This creates a need to improve tools can provide plant-available Si (PAS) and increase its use efficiency (UE), especially under sandy soil conditions. This study was conducted to estimate Si use efficiency (Si-UE) in sandy soil treated by a hydrogel (water-absorbing polymer) loaded by Si. A field experiment was carried out using a hydrogel (H, 0.7 g kg−1 soil) that was mixed with quartz silica (S, 98.4% SiO2) to give HS homogenous mixtures with three mixing ratios 1:0.5 (HS1), 1:1 (HS2) and 1:1.5 (HS3). The HS mixture was sprayed by potassium humate solution (K-humate, 0.5 mL g−1 hydrogel) to obtain HS1K, HS2K, and HS3K treatments. All treatments were mixed with soil subsurface before wheat (Triticum aestivumL.) cultivation. Results showed that wheat yield and seed yield (t ha−1) increased significantly by applied treatments compared to the control C in the range 9.52–23.80% and 2.59–30.60%, respectively. The HS3 treatment significantly increased the total nitrogen N (mg kg−1) in seeds by 34.99%, phosphorus P by 17.46%, and potassium K by 4.84%. Available Si in soil (mg kg−1) increased in the order HS1 < HS2 < HS3, and with K-humate in the order HS1K < HS2K < HS3K. Total Si (g kg−1) in wheat seeds increased significantly in the order HS1 < HS2 < HS3, and HS1K < HS2K < HS3K with K-humate. Silicon use efficiency may decrease as the rate of applied Si increases.