Effect of Treating Field Spatial Variability in Winter Wheat at Different Resolutions

ABSTRACT

This study was conducted to determine the scale at which spatial variability should be treated using an in-season nitrogen fertilization optimization algorithm (NFOA). Treatments included variable nitrogen (N) rate applications at three resolutions (0.84, 13.4, and 26.8 m²), two treatments of 90 kg N ha⁻¹ fixed rate applied preplant or midseason, and a check plot. Treatments were arranged in a completely randomized design with three replications established at two locations for three years. On average, the NFOA-based N rates achieved a higher N use efficiency (NUE) of 41% compared with only 33% of the 90 kg N ha⁻¹ fixed rate applied midseason. The highest NUE among the NFOA-based N rate treatments was 56% at 13.4 m² resolution. These benefits were attributed to a large reduction in NFOA-based N rate recommendations. Determining midseason N rate requirements using NFOA at 13.4 m² resolution resulted in increased NUE and net return to N fertilizer.

Keywords:

• yield potential
• nitrogen fertilization optimization algorithm
• resolution
• spatial variability
• nitrogen use efficiency

ACKNOWLEDGMENTS

Contribution from the Oklahoma Agricultural Experiment Station.