Water retention in sandy substrates modified by cross‐linked polymeric microgels and their complexes with a linear cationic polymer

New synthetic soil conditioners for anti‐erosion protection of soils in the form of microgel copolymers of N‐isopropylacrylamide and acrylic acid (PAA#) and their interpolyelectrolyte complexes (IPEC#) with different surface charges are tested for optimization of water retention and porous structure in two samples of soil substrates. Water retention curves (WRCs) are used as a fundamental thermodynamic indicator of water holding capacity in soil substrates treated by new polymeric materials. Soil‐hydrological constants, as well as specific surface parameters and pore distribution curves are calculated from the WRCs using the van Genuhten model and the Voronin method in the author's modification. PAA# and anionic IPEC# with high swelling degree at a dose of 1% (by weight) increase field water capacity, available soil water range and specific surface area by 5–6 times for quartz sand, along with reorganizing its structure towards micropore dominance. For loamy sand, the same treatment was less effective with a twofold increase in field moisture capacity, double or triple increase of specific surface area, and an almost constant range of available soil water due to the strong increase of wilting point parameter. Weakly swelling linear polyacrylic acid and cationic IPEC# did not significantly affect properties of both mineral substrates. New soil conditioners, cross‐linked polycomplexes, form microgels in water solution. A method for testing the water‐retaining properties of microgels in soil is described. Microgel and its negative complex have a high ability to retain water in sand/soil, however, cationic complex and linear polymer analogue do not affect the water retention by sand/soil.