A contemporary overview of silicon availability in agricultural soils

Abstract

Our current understanding of silicon (Si) availability in agricultural soils is reviewed and knowledge gaps are highlighted. Silicon is a beneficial rather than essential plant nutrient and yield responses to its application have been frequently demonstrated in Si-accumulator crops such as rice and sugarcane. These crops are typically grown on highly weathered (desilicated) soils where soil solution Si concentrations are low. Increased yields are the result of simultaneous increases in plant tolerance to a wide range of biotic (plant pathogens, insect pests) and abiotic (water shortage, excess salts, metal toxicities) stresses. Traditionally, soil solution Si is viewed as being supplied by dissolution of primary and secondary minerals and buffered by adsorption/desorption of silicate onto Al and Fe hydrous oxide surfaces. In recent years it has become recognized that phytogenic cycling of Si [uptake of Si by plants, formation of phytogenic silica (SiO 2 × nH 2 O) mainly in leaves and subsequent return of this silica to soils in plant litter] is the main determinant of soil solution Si concentrations in natural forests and grasslands. Considerable diminution of the phytogenic Si pool in agricultural soils is likely due to regular removal of Si in harvested products. A range of extractants (unbuffered salts, acetate-based solutions, and acids) can provide valuable information on the Si status of soils and the likelihood of a yield response in rice and sugarcane. The most common Si fertilizers used are industrial byproducts (e.g., blast furnace slag, steel slag, ferromanganous slag, Ca slag). Since agriculture promotes soil desilication and Si is presently being promoted as a broad spectrum plant prophylactic, the future use of Si in agriculture is likely to increase. Aspects that require future research include the role of specific adsorption of silicate onto hydrous oxides, the significance of phytogenic Si in agricultural soils, the extent of loss of phytogenic Si due to crop harvest, the role of hydroxyaluminosilicate formation in fertilized soils, and the effect of soil pH on Si availability.

Physiological Maturation in Seeds of Sweet Soghum for Foliar Fertilisation With Silicate

“…These plants have the capacity to accumulate this mineral in leaf and stem tissue (SOUSA et al, 2013;HAYNES, 2014), promoting indirect beneficial effects, such as resistance to pests, diseases, water scarcity and lodging, and better photosynthetic conditioning, as already demonstrated in sugarcane, maize, rice and grain sorghum (PEREIRA et al, 2004;BARBOSA et al, 2008;SOUSA et al, 2010;SOUSA;KORNDÖRFER;WANGEN, 2010).…”

“…Superscript letters compare varieties within each harvest period and indicate statistical difference by Tukey's test at 5%. Silicate fertilisers are commonly associated with plant protection against herbivory, infectious agents and environmental stress (HAYNES, 2014;GUNTZER;KELLER;MEUNIER, 2012), and avoid the expenditure of energy from plant metabolism on such protection (secondary metabolism), which is thereby better utilised in processes for the accumulation of primary metabolites, essential for the development of the panicles and seeds (SOUSA; KORNDÖRFER;WANGEN, 2010).…”

Managing Water and Soils to Achieve Adaptation and Reduce Methane Emissions and Arsenic Contamination in Asian Rice Production

“…The authors describe initial efforts to improve understanding of the genetic variation in silicon content across rice cultivars, while calling for additional research to identify rice germplasm with high shoot silicon and demonstrating enhanced efficiency of assimilating silicon from soils. The most common forms of silicon fertilizers are industrial byproducts, including the slag from steel mills and blast furnaces [312]. Several naturally occurring minerals are available, such as wollastonite, olivine, and diatomaceous earth, but the cost of mining and transport can exceed the incremental value of use in agriculture [312].…”

“…The most common forms of silicon fertilizers are industrial byproducts, including the slag from steel mills and blast furnaces [312]. Several naturally occurring minerals are available, such as wollastonite, olivine, and diatomaceous earth, but the cost of mining and transport can exceed the incremental value of use in agriculture [312]. A more affordable option might involve the composting of rice straw, for application to rice paddy fields [214].…”

Impact of PlantCatalyst® on Seed Germination and the Hydroponic Culture of Fresh Produce

“…The low concentration of Na 2 SiO 3 would have little effect on the osmolality of the germination solutions, compared to those used in normal seed priming experiments (Azeem et al, 2015;Sharma et al, 2014) and even though low concentrations of silicates have been shown to stimulate crop production, positive effects have only been demonstrated when plants are negatively environmentally impacted, such as when plants are under biotic or abiotic stresses (Azeem et al, 2015;Haynes, 2014).…”