Exploring soil amendment strategies with polyacrylamide to improve soil health and oat productivity in a dryland farming ecosystem: One-time versus repeated annual application

Degraded lands resulting from human and natural causes are widespread in arid and semiarid regions throughout the world. Polyacrylamide (PAM) soil amendments are increasingly used to remediate these degraded lands with the potential benefits on soil health and crop production. However, the scientific evidence of farm-scale use of one-time versus repeated application of PAM has not been reported. The specific objective of this research was to determine the effects of single versus multiple annual PAM application on (a) the dynamic changes in soil quality parameters and (b) oat crop productivity indicators in a dryland farming ecosystem. Our data illustrated that multiple years of annual application of PAM significantly increased soil profile water storage, whereas it reduced soil bulk density and electrical conductivity in the top (0-20 cm) and deeper layers (20-60 cm) over those for the control or single PAM application. The improved soil microecological environments led to increased activities of soil enzymes urease (up to 106%), invertase (94%), and catalase (45%). These in turn promoted soil nutrient turnover and availability (e.g., 76% higher soil alkaline N) and crop growth leading to the improvement in grain protein (up to 31%), protein yield (58%), and partial factor productivity of nitrogen (20%), than did the control treatment. Taken together, these soil and crop performance indicators suggest that repeated annual PAM application for a minimum of 2-3 years would be an effective strategy to combat drought and land degradation and foster sustainable crop production in dryland agriculture under a changing climate scenario.