ИСТИНА

There are two main directions of applying polyelectrolytes as soil amendments: the first one is to use linear polymers. When the soil surface is treated with their solutions, polymer-soil coatings are formed that protect the soil from erosion. However, linear polymers do not directly improve the water-holding capacity of soils. The second direction is associated with the use of hydrophilic cross-linked polymers of network structure, which form hydrogels capable of long-term moisture retention, when swollen in an aqueous medium. They improve the water regime of soils, prevent water evaporation and its gravitational runoff. But such amendments do not have the ability to stabilize the soil structure and do not contribute to the improvement of the mechanical stability of soil. At the same time, there are only few examples of polymeric conditioners with combined effect on soils, which are capable of solving both described problems. This work highlights a super-light-crosslinked copolymer of acrylamide, potassium acrylate, containing biodegradable starch fragments (AM- AK-Starch #), as a multifunctional soil amendment. The content of the crosslinking agent, N, N-methylene-bis-acrylamide, amounted 0.036% by weight. The polymer was synthesized by radical polymerization in a block and milled after drying, with granules of <0.25 mm diameter. We used a commercial copolymer of acrylamide and potassium acrylate, containing 0.2 wt% of the crosslinking agent, with granules of the same size as a comparison sample. The content of carboxyl groups in copolymers, determined by potentiometric titration, amounted 2.2 ∙ 10-3 mol / g for commercial sample and 6.4 ∙ 10-3 mol / g for AM-AK-Starch #. It was shown that the swelling properties of cross-linked polyelectrolytes strongly depend on the conditions of spatial restrictions. In the absence of such restrictions, the copolymer with a high content of carboxyl groups and a lower proportion of a crosslinking agent, AM-AK-Starch#, exhibited higher swelling ratio. When copolymers are placed in the bulk of soil substrates, the advantage has passed to commercial sample, which contains a smaller amount of carboxyl groups, but a larger proportion of the crosslinking agent. The effect obtained is associated with the contribution of the stiffness of the polymer network to polyelectrolyte swelling under conditions of limited space and external pressure. At the same time, both copolymers increased the range of moisture available to plants in sand and soil with low hydrophysical characteristics to the level of well-aggregated fertile loamy soils at application rates of ~ 0.15-0.8 wt%. When 1 wt% AM-AK-Starch # suspension was sprayed over the soil surface, protective coatings were formed, resisting the action of storm wind and water streams. Commercial sample was not able to form protective coatings. This work was supported by the Russian Foundation for Basic Research (grant number 19-29-05036 MK).