A series of biopolymers added to irrigation water were tested for their efficacy in reducing shear-induced erosion
in a laboratory-scale mini-furrow. Suspensions of chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed
cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm, respectively, reduced suspended solids by more
than 80%. None of these biopolymers, however, exhibited the > 90% runoff sediment reduction shown by the present
industry standard, synthetic polyacrylamide polymers, PAM. PAM is effective at concentrations as low as 5 ppm. In
field tests, chitosan solutions were only marginally effective in reducing runoff from the end of a 137 m long furrow,
with indications that results were dependent on the length of the furrow. Sediment runoff of some clay-rich Northern
California soils was reduced by up to 85% by increasing the concentration of exchangeable calcium to > 2.5mM.
Calcium improved the sedimentation of the polyelectrolytic polymers in this study
