Managing Runoff Water Quality from Recently Manured, Furrow-Irrigated Fields

摘要

Nutrient losses in furrow irrigation runoff potentially increase when soils are amended with manure. We evaluated the effects of tillage, water-soluble polyacrylamide (WSPAM), and irrigation management on runoff water quality during the first furrow irrigation on a calcareous silt loam soil that had received 45 Mg ha(-1) (dry wt.) dairy manure applied in the fall. In Exp. 1, the amended soil was rototilled and irrigated that fall; furrow inflows were either treated with 10 mg L-1 WSPAM injected into furrow inflows only during furrow advance (Fall-WSPAM), or were untreated (Fall-Control). In Exp. 2, the first irrigation on the amended soil was delayed until the following spring and treatments included rototilled WSPAM (Spring-WSPAM), with WSPAM applied as in Exp. 1, and untreated rototilled (Spring-Control) or moldboard-plowed soils (Spring-Plow). Experiment 3 also delayed irrigation until spring and compared conventional vs. buried lateral furrow irrigation systems. We measured sediment, dissolved organic C (DOC), NO3-N, NH4-N, dissolved reactive P (DRP), and total P (TP) concentrations in irrigation furrow runoff. Runoff mass losses from Fall-Control furrows were relatively large: sediment, 4505 kg ha-1; DOC, 10.7 kg ha(-1); NO3-N, 28.1 g ha(-1); NH4-N, 68.1 g ha(-1); DRP, 132 g ha(-1); and TP, 3381 g ha(-1). Delaying the first irrigation until spring or treating the fall irrigation with WSPAM reduced runoff component losses by 80 to 100% relative to Fall-Control. The Spring-Plow treatment reduced runoff DRP mass losses by similar to 60% compared with Spring-Control. The buried lateral furrow system decreased runoff mass losses for sediment, DOC, and TP by >80% relative to conventional irrigation. This research demonstrated that several management practices may be successfully used to substantially reduce offsite nutrient transport during the first irrigation on furrow-irrigated, manure-amended fields.