Irrigated water, polymer application in

In the past decade, water-soluble polyacrylamide (PAM) was identified as an environmentally safe and highly effective erosion preventing and infiltration enhancing polymer when applied in furrow irrigation water at 1 mg L-1 - 10 mg L-1 , i.e., 1 ppm- 10 ppm.[1-9] Various polymers and biopolymers have long been recognized as viable soil conditioners because they stabilize soil surface structure and pore continuity. The new strategy of adding the conditioner, high molecular weight anionic PAM, to irrigation water in the first several hours of irrigation implies a significant costs savings over traditional application methods, in which hundreds of kilograms per hectare of soil additives are tilled into the entire (15 cm deep) soil surface layer. By adding PAM to the irrigation water, soil structure is improved in the important 1-5 mm thick layer at the soil/water interface of the 25%-30% of field surface contacted by flowing water. In 1995, the U.S. Natural Resource Conservation Service (NRCS) published a PAM-use conservation practice standard for PAM-use in irrigation water." 01 A 3-year study[21 applying these standards showed that PAM at dosage rates of 1 kg ha-1 -2 kg ha-1 per irrigation eliminated 94% (80%-99% range) of sediment loss in furrow irrigation runoff, while increasing infiltration 15%-50%. Seasonal application rates using the NRCS standard typically total 3 kg ha -1 -5 kg ha-1 . As PAM-use is one of the most effective and economical technologies for reducing soil-runoff, it has branched into stabilization of construction sites and road cuts, with formal statewide application standards set in Wisconsin and several southern states. Recent studies with biopolymers such as charged polysaccharides,[11-143 whey," 51 and industrial cellulose derivatives[11.141 introduce potential biopolymer alternatives to PAM