Ameliorating Properties of Silsesquioxane Humic Systems: a Model Experimentтезисы доклада

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[1] Ameliorating properties of silsesquioxane humic systems: a model experiment / A. R. Ziganshina, O. I. Filippova, A. V. Yudina et al. // Book of Abstracts. Fourth International Conference of CIS IHSS on Humic Innovative Technologies From Molecular Analysis of Humic Substances – to Nature-like Technologies (HIT-2017). — ООО "КЛУБ ПЕЧАТИ" Москва, 2017. — P. 141–141. An increasing anthropogenic impact on agricultural land results in soil deterioration processes mainly due to soil structure degradation. Degradation of the soil structure of the arable horizon has been marked in the vast areas al over the world. The latter led to drastically reduced soil fertility due to poor conditions of crops growing. Therefore, searching for new methods of soil improvement aimed primarily at improving soil structure is of a great importance. An introduction the humic acids (HA) modified with siloxanes (so called silsesquioxane humic systems, Si-HA) seems to be one of the most promising approach. Despite the fact that the possibility of using Si-HA has already been shown earlier [1], there are still no studies aimed at comprehensive evaluate their ameliorative properties. So, the goal of our work was to conduct a comprehensive evaluation of Si-HA ameliorating properties including both evaluation of their effect on soil structure, their sorption on soil and their toxicity assessment towards higher plants and soil microflora as well. To reach this goal, a model experiments with soil samples of arable horizon of sodpodzolic soil (pH 5.3, OC 1.83%, N 0.12%) were saturated with HA or Si-HA at different rates followed by estimation of HA or Si-HA desorption from soil, measuring soil substrateinduced respiration (SIR) according to [2], estimation of stable microaggregates using laser analyzer of particle size Microtrac Bluewave (Microtrac, USA) and bioassay of soil water extracts using wheat seedlings. To follow alteration of soil humus composition, a ratio of CHA/CFA was also measured. Samples saturated with distilled water were used as blank ones. Si-HA was synthesized based on coal HA using (3-aminopropyl)triethoxysilane (APTES) according [1]. Our results demonstrated that additional stable microaggregates in the soil in the presence of Si-HA formed when the rate of Si-HA was 0.75% by weight of the soil or higher. That rate corresponded to humus content ca. 4% that is usually considered as optimum humus content in terms of humus’ properties as“soil glue” [3]. Si-HA sorbed mainly irreversible by soil, and the amount of desorbed organic carbon did not exceed 10% of the input. That finding was consistent with the concept of adsorption Si-HA due to the formation of siloxane bonds. The latter was indirectly confirmed also by closeness of CHA/CFA ratio in case with soil saturation with Si-HA to the blank values (0.760.03 for Si- HA versus 0.620.03 for blank), while soil saturation with unmodified HA resulted in significant increase in CHA/CFA ratio (1.080.19). Si-HA stimulated SIR (probably, due to release of nitrogen of amino groups of APTES) and were not toxic for wheat seedlings up to the rate 1.25% by weight of the soil. So, the obtained results allowed to conclude that further study of Si-HA as ameliorating soil agents is of great promise. References 1. Volikov A.B. et al. // Catena. 2016. 137:229–236. 2. Ananieva N.D et al. // Pochvovedenie. 2009. 9:108–1116. (in Russian) 3. Antipov-Karataev et al. // Soil aggregate and methods of its study. Academy of USSR Publisher. 1948. (in Russian) This research was supported by the Russian Science Foundation grant 16-14-00167.

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