Maize (Zea mays L.) Grain Yield and Nitrogen Uptake Response to Preplant Nitrogen Placement At Different Distances Away From the Row.

Equipment with RTK Global Positioning Systems correction can provide sub-inch accuracy for N application.   When nitrogen (N) is applied closer to the row, mid-season,  there is a positive response to grain yield. This study was conducted to evaluate the effect of preplant N placement at different distances from maize rows on grain yield, and nitrogen use efficiency (NUE).  Field studies were established at Lake Carl Blackwell (LCB), OK on a Pulaski fine sandy loam (coarse loamy, mixed, superactive, nonacid, Udic Ustifluvents) and at Hennessey, OK on a Bethany silt loam (fine, mixed, superactive, thermic Pachic Paleustolls).  Preplant N rates were 0, 56, 112, and 224 kg N ha^-1 with the 224 kg N ha^-1 used as a non-limiting reference.  Preplant distances from the row included 0, 7.6, 15.2, 25.4, 38.1 cm and were achieved by using an RTK equipped tractor. Treatments were arranged in a randomized complete block with 3 replications.

Expected results- Grain yield increased with closer preplant placement of N in relation maize row. Nitrogen applications further away from the row decreased N uptake, and NUE.  With the current accuracy and availability of RTK-GPS correction, preplant N applications should be made within 15 cm of where expected corn rows will be placed in order to increase N use efficiency.