Preventing Soil Erosion with Polymer Additives
1999
Orts, William J. | Sojka, Robert E. | Glenn, Gregory M. | Gross, Richard A.
The agricultural use of polyacrylamide, PAM, as an additive in irrigation water has grown rapidly since commercial introduction in 1995, with over l million acres treated in 1998. PAM provides both economic and environmental benefits by improving water infiltration and reducing up to 98% of erosion induced soil losses -- a yearly saving of tons of topsoil per acre. With as little as 5 ppm of PAM in the first irrigation water to run across the field, soil cohesion increases enough to prevent particle detachment and erosion. Stable soil/polymer flocs result from PAM's high molecular weight (typically > 12 million) and its affinity to soil via coulombic and Van der Waals attraction. Although water soluble linear PAM is the only class of commercial polymer presently used to reduce erosion during irrigation, other polymer additives have shown some potential. Biopolymers such as chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils reduce shear-induced erosion; however concentrations at least 6-10 times higher than PAM are required to obtain the > 90% runoff sediment reduction shown by commercial PAM. The application of PAM in agricultural irrigation water and potential biopolymer alternatives to PAM are discussed.
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