Nitrogen uptake efficiency in maize production using irrigation water high in nitrate

Abstract

In order to achieve efficient use of nitrogen (N) and minimize pollution potentials, producers of irrigated maize (Zea mays L.) must make the best use of N from all sources. This study was conducted to evaluate crop utilization of nitrate in irrigation water and the effect N fertilizer has on N use efficiencies of this nitrate under irrigated maize production. The study site is representative of a large portion of the Central Platte Valley of Nebraska where ground water nitrate-N (NO₃-N) concentrations over 10 mg L⁻¹ are common. Microplots were established to accommodate four fertilizer N rates (0, 50, 100, and 150 kg ha⁻¹) receiving irrigation water containing three levels of NO₃-N (0, 10, 20 mg L⁻¹). Stable isotope¹⁵N was applied as a tracer in the irrigation water for treatments containing 10 and 20 mg L⁻¹ NO₃-N. Plots that did not receive nitrate in the irrigation water where tagged with¹⁵N fertilizer as a sidedress treatment. Sidedressed N fertilizer significantly reduced irrigation-N uptake efficiencies. When residual N uptake is added to first year plant usage, total irrigation NO₃-N uptake efficiencies are similar to total sidedress N fertilizer uptake efficiencies for our cropping system over the two year period. Efficiency of irrigation-N use depends on crop needs and availability of N from other sources during the irrigation season.