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