Biogenic amorphous silica as main driver for plant available water in soils

Abstract

More frequent and longer drought periods are predicted threatening agricultural yield. the capacity of soils to hold water is a highly important factor controlling drought stress intensity for plants. Biogenic amorphous silica (bASi) pools in soils are in the range of 0-6% and are suggested to help plants to resist drought. In agricultural soils, bASi pools declined to values of ~1% or lower) due to yearly crop harvest, decreasing water holding capacity of the soils. Here, we assessed the contribution of bASi to water holding capacity (WHC) of soil. Consequently, ASi was mixed at different rates (0, 1, 5 or 15%) with different soils. Afterwards, the retention curve of the soils was determined via Hyprop method. Here we show that bASi increases the soil water holding capacity substantially, by forming silica gels with a water content at saturation higher than 700%. An increase of bASi by 1% or 5% (weight) increased the water content at any water potential and plant available water increased by up to > 40% or > 60%, respectively. Our results suggest that soil management should be modified to increase bASi content, enhancing available water in soils and potentially decreasing drought stress for plants in terrestrial ecosystems.

Silicon Cycling in Soils Revisited

“…This increase in water-holding capacity by ASi might be explained by a silica gel formation from polysilicic acid or colloidal amorphous silica, in the pH range of 4 to 7 with a maximum at pH 5 [ 277 ]. Most recently, amorphous silica has been shown to strongly increase the water-holding capacity and plant-available water in soils [ 213 ]. It was shown that an increase in ASi by 1% or 5% (by weight) increased plant-available water by up to >40% or >60%, respectively [ 213 ].…”

“…Most recently, amorphous silica has been shown to strongly increase the water-holding capacity and plant-available water in soils [ 213 ]. It was shown that an increase in ASi by 1% or 5% (by weight) increased plant-available water by up to >40% or >60%, respectively [ 213 ]. However, a comprehensive picture of the effect of ASi contents on the water-holding capacity of soils is still missing.…”

“…Conditions with high Si concen- Overall, the above-mentioned literature suggests that ASi is a dominant fraction of andosols/andisols. This high share of ASi might at least partly explain why andosols/andisols exhibit such a high water-holding capacity and nutrient availability (especially non-allophane andosols), properties which have been attributed to ASi and silicic acid originating from ASi [127,212,213] (see below). Only under low or high (<5 and >7) soil pH of andosols/andisols can a high concentration of Al in soil pore water readily leading to a formation of allophane be assumed [207,214], which suggests a minor role of ASi at low soil pH.…”

An Overview on the Potential of Silicon in Promoting Defence Against Biotic and Abiotic Stresses in Sugarcane

“…However, water-holding capacity of soil is a vital factor which controls the intensity of drought stress in plants. A recent study revealed that most of the effect of Si on drought is happening in the soil and the plant effect may be only a consequence of those soil effects (Schaller et al 2020).…”

Geo-Agriculture: Reviewing Opportunities through Which the Geosphere Can Help Address Emerging Crop Production Challenges

“…Silicon is now widely recognised for its diverse modes of supporting plant growth under drought conditions [106]. An increase in biogenic amorphous silica from 1 wt % to 5 wt % in soil can increase the plant-available water content by >60% [107]. Silicates are transported through roots with water as dissolved silicic acid and deposited in cell lumens, cell walls, and intercellular spaces of roots and leaves as amorphous hydrated silica (SiO 2 •H 2 O) [108].…”