Maize (Zea mays L.) Grain Yield Response to by-Plant Nitrogen Fertilization.

Crop yields are affected by the rate and method of nitrogen (N) fertilizer application.  This study was conducted to determine the effects of applying N rates by plant, based on mid-season predictions of maize grain yield potential.  The mid-season sidedress application N rate was determined using NDVI sensor readings, plant height, and distance between plants (competition factor).  The effects of by plant N rate were investigated at the R.L. Westerman Irrigation Research Facility near Stillwater, Oklahoma on a Pulaski fine sandy loam (coarse-loamy, mixed, superactive, nonacid, thermic Udic Ustifluvents), at the Eastern Research Station near Haskell, Oklahoma on a Taloka silt loam (fine, mixed, active, thermic Mollic Albaqualfs), and at Hennessey, Oklahoma on a Bethany silt loam (fine, mixed, thermic Pachic Paleustolls).  Significant grain yield differences have been observed at the by plant level, demonstrating plant to plant variability.  This work suggests the need for application of N by plant to obtain optimum yields and that will be needed to maximize returns on investment.