Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 12, 2010
Publication Date: August 2, 2010
Citation: Lentz, R.D., Lehrsch, G.A. 2010. Nutrients in runoff from a furrow-irrigated field after incorporating inorganic fertilizer or manure. Journal of Environmental Quality. 39:1402-1415(2010). Interpretive Summary: Use of dairy manure to supply crop nutrients is gaining broader acceptance as the cost of fertilizer rises; however, few have studied how manure amended soils may influence the water quality of runoff from furrow irrigated fields. In this two-year study we established furrow irrigated field plots that were treated with inorganic nitrogen fertilizer, manure, or left untreated. During subsequent furrow irrigations, we measured nutrient concentrations and mass losses in runoff. The research showed that both inorganic nitrogen fertilizer and manure increased runoff nitrate concentrations and losses from furrow irrigated plots. Compared to controls, manure treatment also increased dissolved phosphate and potassium concentrations in runoff. Mass losses for the phosphate and potassium were 2.0 to 2.4 times greater in manure treatments than in controls. In furrow irrigated soils, the effect of nutrient additions on runoff water quality varies with the nutrient, amount and timing of application, and whether inorganic fertilizer or manure was applied. This information will 1) help environmental stewards better understand the potential impacts of irrigated farm management on runoff water quality and 2) guide the development of practices that will reduce the impact of agricultural runoff on surface waters.
Technical Abstract: Use of dairy manure to supply crop nutrients is gaining broader acceptance as the cost of fertilizer rises; however, there are concerns regarding manure’s effect on water quality. In 2003 and 2004, we measured sediment, NO3-N, NH4-N, K, dissolved reactive P (DRP), and total P (TP) concentrations in runoff from furrow irrigated field plots (6-7 irrigations/y). Annual treatments included: (M) 13 to 34 Mg/ha stockpiled dairy manure; (F) 78 to 195 kg N/ha inorganic N fertilizer; or (C) control--no amendment. Available N in manure applied each year was similar to amounts applied in fertilizer. Constituent concentrations (mg/L) in runoff ranged widely: sediment, 10 to 50,000; NO3-N, 0 to 4.07; NH4-N, 0 to 2.28; K, 3.6 to 46.4; DRP, 0.02 to 14.3; and TP, 0.03 to 41.5. Fertilizer and manure treatments increased irrigation mean values for NO3-N runoff concentrations (C=0.21, F=0.26, M=0.30 mg/L) and mass losses (C=0.33, F=0.42, M=0.50 kg/ha) relative to controls. Manure treatment also increased mean irrigation runoff DRP (C=0.08, F=0.09, M=0.19 mg/L) and K concentrations (C=0.62, F=0.79, M=1.13 mg/L) compared to controls. Average DRP and K runoff mass losses were 2.0x to 2.4x greater in manure treatments than in controls. Nutrient amendments did not affect season-long cumulative infiltration or seasonal runoff mass losses for sediment or TP. Runoff DRP and inorganic N losses appeared to be influenced more by the timing of the amendment application and environmental conditions, than by the quantity of nutrients applied. Incorporation of nutrients, whether from fertilizer or manure, into furrow irrigated soils can potentially increase nutrient losses in irrigation runoff, depending on the nutrient, amount and timing of application, and whether inorganic fertilizer or manure was applied.