In-Season Nitrogen Management of Sub-Surface Drip Irrigated Corn.
Richard Ferguson and S. Irmak. Univ of Nebraska, Dept of Agronomy & Horticulture, Lincoln, NE 68583-0724
Supplies of irrigation water have declined in recent years in the Great Plains due to multiple years of drought and increasing competition for limited water. Consequently, producers are exploring options to increase irrigation water use efficiency. Sub-surface drip irrigation (SDI) has been used for many years on higher value crops, but has historically not been cost effective for commodity grains such as corn. A research study was conducted in 2004-2006 at the South Central Agricultural Laboratory in Nebraska to investigate irrigation and fertilizer nitrogen (N) management practices for SDI corn. Treatments included irrigation scheduling to meet 100, 75 and 50% of ET, and N scheduling of 75% preplant/25% fertigation, 25% preplant/75% fertigation, or 25% preplant/balance reactive. Reactive N scheduling was determined by chlorophyll meter measurements relative to a reference treatment between V8 and R1 growth stages. SDI treatments were compared to the current practice of furrow irrigation with preplant N application. In 2004, excessive soil residual nitrate-N from the drought-stressed crop the previous year prevented implementation of N treatments. In 2005, there were no significant differences in grain yield among N management strategies, with an average yield of 12.8 Mg ha-1. However, fertilizer N applied with the reactive approach was slightly less than other approaches, and resulted in a trend for less residual nitrate-N to a depth of 2 m. There was also a trend for less residual nitrate-N with all SDI treatments compared to furrow irrigation, while grain yield from furrow and 100% ET SDI treatments were the same. In both 2004 and 2005, grain yield tended to be optimized at 75% ET with SDI application, indicating greater water use efficiency with SDI placement.