Gel-Forming Soil Conditioners of Combined Action: Laboratory Tests for Functionality and Stability.

The research analyzes technological properties and stability of innovative gel-forming polymeric materials for complex soil conditioning. These materials combine improvements in the water retention, dispersity, hydraulic properties, anti-erosion and anti-pathogenic protection of the soil along with a high resistance to negative environmental factors (osmotic stress, compression in the pores, microbial biodegradation). Laboratory analysis was based on an original system of instrumental methods, new mathematical models, and the criteria and gradations of the quality of gels and their compositions with mineral soil substrates. The new materials have a technologically optimal degree of swelling (200−600 kg/kg in pure water and saline solutions with 1−3 g/L TDS), high values of surface energy (>130 kJ/kg), specific surface area (>600 m2/g), threshold of gel collapse (>80 mmol/L), half-life (>5 years), and a powerful fungicidal effect (EC50 biocides doses of 10−60 ppm). Due to these properties, the new gel-forming materials, in small doses of 0.1−0.3% increased the water retention and dispersity of sandy substrates to the level of loams, reduced the saturated hydraulic conductivity 20−140 times, suppressed the evaporation 2−4 times, and formed a windproof soil crust (strength up to 100 kPa). These new methodological developments and recommendations are useful for the complex laboratory testing of hydrogels in small (5−10 g) soil samples.

Gel-Forming Soil Conditioners of Combined Action: Field Trials in Agriculture and Urban Landscaping.

The article summarizes multivariate field trials of gel-forming soil conditioners for agriculture and urban landscaping in various climatic conditions from arid (O.A.E., Uzbekistan) to humid (Moscow region, Russia). The field test program included environmental monitoring of weather data, temperature, water-air regimes, salinity, alkalinity, and biological activity of various soils (sandy and loamy sandy Arenosols, Retisols, loamy Serozems), productivity and yield of plants (lawns, vegetables) and their quality, including pathogen infestation. The evolutionary line of polymer superabsorbents from radiation-crosslinked polyacrylamide (1995) to the patented "Aquapastus" material (2014-2020) with amphiphilic fillers and biocidal additives demonstrated not only success, but also the main problems of using hydrogels in soils (biodegradation, osmotic collapse, etc.), as well as their technological solutions. Along with innovative materials, our know-how consisted in the intelligent soil design of capillary barriers for water accumulation and antipathogenic and antielectrolyte protection of the rhizosphere. Gel-forming polymer conditioners and new technologies of their application increase the productivity of plant crops and the quality of biomass by 30-50%, with a 1.3-2-fold saving of water resources and reliable protection of the topsoil from pathogens and secondary salinization. The results can be useful to a wide range of specialists from chemical technologists to agronomists and landscapers.