Soil-Based, Field-Specific Nitrogen Fertilizer Recommendations in Corn.

Current research findings will highlight research focused on correlating and calibrating a soil-based N test for the determination of field-specific N fertilizer recommendations in Mid-South irrigated corn (Zea mays L.) production. Nitrogen response trials were established throughout the primary corn producing regions of Arkansas from 2013 to 2016. Nitrogen fertilizer rates ranged from 0 to 360 kg N ha^-1 and were split applied between an at-planting and two in-season applications. Soil samples were collected in 15 cm increments down to a depth of 60 cm prior at the V4-V6 growth stage and were analyzed for alkaline-hydrolyzable N, NH₄-N, and NO₃-N. Our results have demonstrated the ability of using both organic and inorganic-N to accurately determine site-specific N recommendations for furrow-irrigated Mid-South corn production. Current pre-sidedress NO₃-N recommendations for corn production in the Mid-West do not appear to apply for Mid-South production systems. There were several sites within these trials that continued to have a positive response to the addition of N fertilizer even when there was greater than 21 mg NO₃-N kg soil^-1 to a depth of 30 cm. Calibration of several different soil test methods including soil NO₃-N showed strong relationships for predicting N fertilizer needs to achieve 95% relative grain yield. Similar to other researchers, soil-based N tests for corn production are tightly linked to soil texture and drainage classification.