Improving infiltration of irrigated Mediterranean soils with polyacrylamide

The effects of continuous (1.0 mg/l) and concentrated (10 mg/l) irrigation water-added polyacrylamide (PAM) on infiltration of a highly erodible Medit erranean soil were studied using recirculating furrow infiltrometers. Polya crylamide avoided the seal formation observed in the wetted surface of the control furrow and helped to maintain higher infiltration rates for both PA M treatments. Mean final cumulative infiltration for the continuous and con centrated PAM experiments increased by 20 and 14%, respectively, as the res ult of reduced seal formation and surface sealing. Steady-state furrow infi ltration rates, evaluated with disc infiltrometers 15 h after irrigation an d under soil water tensions of 40 and 100 mm, confirmed the infiltration be nefit of PAM treatments. Unsaturated hydraulic conductivity calculated unde r the same tensions revealed that the PAM-treated furrows were about 95% mo re permeable than the control. Polyacrylamide application also increased av erage saturated conductivity by 168% because of more unblocked pores in the treated furrows. The ability of PAM to influence surface soil conditions a nd improve infiltration can greatly enhance management of irrigated Mediter ranean soils by allowing longer irrigation and higher inflow rates. Applica tion of 10 mg/l in the inflow only during the advance phase of the irrigati on can reduce labour, and ensures that loss of PAM from furrow tail water i s minimized and that quantities applied during the season are reduced. (C) 2000 Silsoe Research Institute.