Biopolymer additives for the reduction of soil erosion losses during irrigation

High molecular weight, synthetic polyacrylamides (PAM) are relatively large, water soluble polymers that are used increasingly by farmers to prevent erosion and increase infiltration during irrigation. A lab-scale erosion test was conducted to screen biopolymer solutions for a similar efficacy in reducing shear-induced erosion. In lab-scale mini-furrow tests, chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm respectively, reduced suspended solids in the runoff water from test soil. None of these biopolymers, however, exhibited the >90% runoff sediment reduction shown by PAM at concentrations as low as 5 ppm. Preliminary field tests results showed that chitosan solutions were only marginally effective in reducing runoff from a 137m long furrow. There were indications that results were dependent on the length of the furrow. Erosion of some clay-rich soils from Northern California was reduced up to 85% by increasing the concentration of exchangeable calcium to >2.5mMole, with or without the addition of polymer additives.