The Influence of Enhanced Efficiency Fertilizers On Nitrate Leaching From Irrigated Maize.

Nitrogen fertilizer can be a challenge to manage on coarse-textured irrigated soils for maize production. Enhanced efficiency nitrogen fertilizers have the potential to protect against N loss via multiple pathways. Over a five year period, a study in Nebraska evaluated various enhanced efficiency fertilizers for their potential to increase nitrogen fertilizer use efficiency and reduce nitrate leaching. Granular matrix water potential sensors were installed at multiple depths in the root zone to estimate unsaturated water flux, and porous ceramic suction lysimeters were installed at the bottom of the root zone to measure pore water nitrate concentration. Together these measurements can provide an estimate of nitrate leaching. In two of the five years of the study, weather damaged the crop by flooding or hail, rendering data of limited use. In a year with high potential for ammonia volatilization (2009), less fertilizer N was available for crop uptake or leaching. In a year with a wet spring and early summer and high potential for leaching, nitrate-N leaching loss exceeded 250 kg N ha-1 for some treatments. In all years, polymer-coated urea was the N source least prone to either leaching or volatile loss. Other N sources or additives reduced N loss potential relative to UAN, but to a lesser extent than polymer-coated urea. In 2009 and 2010, grain yield and fertilizer N uptake were significantly higher for polymer-coated urea than for other fertilizer sources.