Lysimeter Study of Nitrogen Fertilizer and Irrigation Rates on Quality of Recharge Water and Corn Yield

Abstract

Abstract Accrual of NO 3 ‐N to groundwater as a result of agricultural practices is a focus of environmental concern. This inquiry was conducted to quantify precisely in a replicated experiment the rate of N loading to groundwater resulting from inputs of N and irrigation water to corn ( Zea mays L.). Input levels were designed to balance potential for high production with minimum loading of NO 3 ‐N to groundwater. Four large (2.4 by 2.4 m and 2.3 m deep) drainage lysimeters with reconstructed Hecla loamy fine sand (Aquic Haploborolls) were employed in this southeast North Dakota study. Grain yields at N fertilizer rates of 95 and 145 kg/ha were 10.3 and 11.3 Mg/ha, respectively. Differences in yield due to irrigation and irrigation by N interaction were nonsignificant. There was no residual effect of N fertilizer on yield. The higher irrigation rate caused increases in drainage of water within about 30 d. The higher rate of N fertilizer, however, was not reflected by increased concentration of NO 3 ‐N in the drainage water until 325 d after application. The increased concentrations then persisted to 500 d. Flow‐weighted means of NO 3 ‐N concentrations for this period were 8.6 and 12.3 mg/L for the low and high N rates, respectively. For this soil and climate, irrigation and N management can be tailored to produce NO 3 ‐N concentrations below 10 mg/L with continuous corn. However, the 5:1 economic return produced by 50 kg/ha of incremental N fertilizer means that producers are unlikely to adopt the needed practices without incentives.