Sorption competition with natural organic matter as mechanism controlling silicon mobility in soil

Abstract

Growing evidence of silicon (Si) playing an important role in plant health and the global carbon cycle triggered research on its biogeochemistry. In terrestrial soil ecosystems, sorption of silicic acid (H4SiO4) to mineral surfaces is a main control on Si mobility. We examined the competitive sorption of Si, dissolved organic matter, and phosphorus in forest floor leachates (pH 4.1–4.7) to goethite, in order to assess its effects on Si mobility at weathering fronts in acidic topsoil, a decisive zone of nutrient turnover in soil. In batch sorption experiments, we varied the extent of competition between solutes by varying the amount of added goethite (α-FeOOH) and the Si pre-loading of the goethite surfaces. Results suggest weaker competitive strength of Si than of dissolved organic matter and ortho-phosphate. Under highly competitive conditions, hardly any dissolved Si (< 2%) but much of the dissolved organic carbon (48–80%) was sorbed. Pre-loading the goethite surfaces with monomeric Si hardly decreased the sorption of organic carbon and phosphate, whereas up to about 50% of the Si was released from surfaces into solutions, indicating competitive displacement from sorption sites. We conclude sorption competition with dissolved organic matter and other strongly sorbing solutes can promote Si leaching in soil. Such effects should thus be considered in conceptual models on soil Si transport, distribution, and phytoavailability.

How much carbon can be added to soil by sorption?

“…The black line is the median Q sp and the gray shading represents the 5th and 95th percentile range excluded Gelisols and Histosols from this analysis because they were poorly represented in the laboratory sorption experiments, high-latitude profiles from other soil orders were estimated to have consistently low Q sp , implying that most mineral sites are already occupied by organic C. Treating grid cells as independent, there is a weak, negative correlation (q = 0.27) between Q sp in units of stock and total organic carbon stock (kg m -2 ), suggesting that soils with high initial organic C stocks will have less capacity to accrue more C via sorption. The negative influence of organic matter on sorption of various chemical species has been observed in previous sorption experiments (Johnson and Todd 1983;Klotzbücher et al 2020;Redman et al 2002).…”

Silicon Cycling in Soils Revisited

“…The occurrence and concentration of silicic acid in solution is regulated by: (i) polymerization/depolymerization; (ii) complexation of silicic acid with inorganic and organic ligands; but also by (iii) adsorption/desorption to or from mineral or organic surfaces [72]. The binding strength of monosilicic acid to, e.g., goethite, at short reaction times is low [73]. Adsorption of polysilicic acid to mineral surfaces is much faster (some minutes) compared to sorption of monosilicic acid (sorption within weeks), because polysilicic acid has a higher binding affinity than monosilicic acid [61].…”

Silica nanoparticles as novel sustainable approach for plant growth and crop protection

“…Phytoavailability of Si depends on numerous parameters such as Si quantity in soil, organic material, soil pH, and soil humidity. Plants uptake Si through two expected systems, such as active and passive transportation, based on plant varieties (Klotzbücher et al, 2020). Quite a few plant varieties are identified for their passive uptake of Si as grasses (Attia and Elhawat, 2021;Ryalls et al, 2018).…”