Managing Runoff Water Quality from Recently Manured, Furrow-Irrigated Fields
- R. D. Lentz * and
- D. T. Westermann
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 ∼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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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