Evaluation of Nitrogen and Irrigation Management for Corn Production using Water High in Nitrate

A field-calibrated computer model was used to study the interaction of nitrogen (N) and water management for corn (Zea mays L.) production on sandy soils in the central Platte Valley of Nebraska. Most irrigation in this area is with pumped groundwater which at many locations contains from 10 to 30 ppm (or more) of nitrate nitrogen (NO⁻₃-N). Simulation results were used to estimate the effects of irrigation management, N management, and the NO⁻₃-N concentration of the irrigation water upon N uptake by corn, the uptake efficiency of groundwater and fertilizer N, and the potential for pollution of groundwater with NO⁻₃-N. Nitrogen uptake was also partitioned according to N source (groundwater N, applied fertilizer N, and residual plus mineralized N). Simulation results showed that: 1)Nitrogen uptake was strongly influenced by the amount of fertilizer N and irrigation water applied, and to a lesser extent by the NO⁻₃-N concentration of the irrigation water. There was also a strong interaction of these parameters in determining N uptake. 2)The uptake efficiency of fertilizer N was very sensitive to excess irrigation and only slightly affected by the amount of fertilizer applied or the NO⁻₃-N concentration of the irrigation water. 3)The uptake efficiency of groundwater N was strongly affected by the amount of irrigation water applied and the NO⁻₃-N concentration of the water while the amount of fertilizer applied had a lesser effect. In general, groundwater uptake efficiencies were higher and more stable than fertilizer uptake efficiencies. 4)Excess irrigation increased N uptake from groundwater sources under certain conditions. The groundwater N contribution to uptake was large for irrigation water containing >10 ppm NO⁻₃-N and was primarily determined by the amount of irrigation and the NO⁻₃-N concentration. For 25 ppm NO⁻₃-N irrigation water and small fertilizer applications more N was extracted from the groundwater through irrigation than was lost due to leaching.