Acid-Base Buffering Assessment and Directions of Silicon Compound Transformation in Sod-Podzolic Soil when Used Various Siliceous Rocks
Authors: Kozlov A. V. , Kulikova A. H. 
Published: April 2024

The variability of the main indicators of acid-base buffering of sod-podzolic light-loamy soil was investigated, and the dynamics of the content of monomers and polymers of silicic acid and acid-soluble silica compounds in the soil under conditions of reclamation doses of various siliceous rocks (diatomite, zeolite and bentonite clay 3, 6, 12 t/ha) was described. Zeolite rock and bentonite had a positive effect on the anti-acid buffering ability of the soil, shifting the H+/OH–equilibrium of the system by more than 160 and 20, respectively, depending on the applied dose of the material. The effect of diatomite was manifested in the anti-alkaline region of soil buffering, due to which the H+/OH–-equilibrium index decreased by almost 40%. Against the background of the use of diatom rock and bentonite clay, the content of silicic acid monomers in the soil increased by more than 5 and 4 times, respectively, against the background of the use of zeolite – by more than 2 times. The content of silicic acid polymers in the soil increased up to 3 and 4 times with the use of zeolite and bentonite rocks, respectively. At the same time, the introduction of diatomite into the soil contributed to an increase in the content of H4SiO4 polymers by 5–10 times, depending on the dose of the material. The content of the acid-soluble fraction of silicon compounds in the soil increased by 1.4–2.8 times against the background of different doses of the studied rocks and, in general, had a different dependence depending on the composition of each of them. Based on the revealed irregularities in the content and dynamics of mobile silicon compounds in the soil (monomers and polymers of silicic acids, acid-soluble silica fractions), the characteristic is given and the value of the first proposed indicators describing their dynamic state and directions of transformation – the potential for the formation of monomers (M-ASi) and polymers (P–ASi) is disclosed. H4SiO4, the degree of polymerization (Pm-VSi) and depolymerization (Dm-VSi) of silicic acid, the total content of the loose-amorphous silica fraction (Si-AMF) and the degree of amorphousness of the Si-containing mineral phase of the soil (AMF-VSi). The study of the influence of silicon materials in conditions of sod-podzolic soil revealed that, depending on the qualitative composition and dose of silicon rock, the M-ASi index can increase by 30–80%, and the P-ASi index can be in the range of increase from 0.3 to 3.0 or more times. The processes of polymerization of silicic acid and the decomposition of its polymers into monomers, expressed respectively by Pm-VSi and Dm-VSi, can also actively increase against the background of the interaction of soil with rocks, the measure of change of which is expressed in the order of 10–40% deviation relative to the control. The total content of loose-amorphous silica fraction in the soil, expressed by the SiAMF index, can be determined by the composition of each siliceous rock used as a meliorant. If, when using diatomite, the indicator can decrease by almost 30%, then when using zeolite and bentonite clay, it can increase by 30–100%, depending on the dose. Similarly, the indicator of the degree of amorphousness of the silicon-containing part of the soil substance (AMF-VSi) can also change.