Binary Soil Ameliorants Composed of Synthetic Polyanion and Natural Humates

Abstract

Polymer-based soil ameliorants are considered effective tools to protect soil from wind and water erosion. In the article, five promising modern ameliorants were examined: hydrolyzed polyacrylonitrile (HYPAN, synthetic polyanion), two commercial humic products (potassium humates) and two binary mixtures composed of HYPAN and humates at 10/1 wt/wt ratio, with a special attention to their effects on soil structuring, anti-erosion and hydrophysical properties. The polymers were dissolved in water and the resulting aqueous formulations were 1) sprayed on the surface or 2) injected into the sandy loam soil. The obtained polymer-soil constructs were comprehensively tested for mechanical strength, aggregate composition, anti-erosion stability, water retention capacity and biocompatibility with the following main conclusions. When sprayed over the soil, the formulations penetrate the soil to a depth of 0.5 cm. Drying the soil with deposited polymers results in polymer-soil coatings with mechanical strength varied from 0.7–1.3 kg/cm² for humates to 4.1–6.7 kg/cm² for HYPAN-based formulations. HYPAN coatings provide a 100% soil resistance at an air flow speed of 72 km/h and only 5–7% loss of soil when re-watering. Treatment of soil with HYPAN-based formulations results in a higher water capacity, better retention of water and increased content of agronomically valuable aggregates 0.25–1 mm in size from 34 to 51 wt %. Addition of humates to HYPAN solutions stimulates plants growth. The results obtained are important to develop polymer ameliorants with anti-erosion, water-retaining and biostimulating properties.