Adjusting Midseason Nitrogen Rate Using a Sensor-Based Optimization Algorithm to Increase Use Efficiency in Corn

ABSTRACT

This study was conducted to formulate an in-season nitrogen (N) fertilization optimization algorithm (NFOA) to estimate midseason N rates that maximize corn (Zea mays L.) growth and minimize fertilizer inputs. Treatments included: a zero kg N ha⁻¹; three treatments of 134 kg N ha⁻¹ fixed rate applied in split, preplant, or sidedress; two treatments of 67 kg N ha⁻¹ fixed rate preplant or sidedress applied; three NFOA-based midseason N rates (RI-NFOA, RICV-NFOA, flat-RICV-NFOA) with (67 kg N ha⁻¹) and without preplant N; and two resolutions (0.34 and 2.32 m²) tested for RICV-NFOA only. With the 67 kg N ha⁻¹ preplant application, midseason RI-NFOA-based N rates resulted in an N use efficiency (NUE) of 65% while the 134 kg N ha⁻¹ fixed rate split applied had 56% NUE. Using the RICV-NFOA, NUE and net returns to N fertilizer were higher when spatial variability was treated at 2.32 m² resolution.

Keywords:

• Corn
• yield potential
• nitrogen fertilization optimization algorithm
• response index
• coefficient of variation
• normalized difference vegetation index

Notes

^±Date in month-day-year.

^§Lake Carl Blackwell.

^¶Sensing dates done between V8-V9 leaf growth stages.

^§Determination of critical CV was based from plant population.

^‡Average NDVI of NFOA treatments.

^†Adjusted in-season response index, determined by dividing average Normalized Difference Vegetation Index (NDVI) between V8-V9 leaf growth stage of Treatment 6 (134 kg ha⁻¹ preplant) by the Check plot. Adjustment was made using the equation (RI_NDVI× 1.64) - 0.528.

^§Response index at harvest, determined by dividing the grain yield of the highest preplant N fertilized plots by the Check plot.

^¥Critical CV used in the algorithm.

^¶Determined from the equation: critical CV = (−0.0003*plant population) + 36.315.

^¥Full description is presented in Table 2.

^¥Full description is presented in Table 2.

^¥Full description is presented in Table 2.

^§Estimated by subtracting the grain N uptake of the check plot from the fertilized plot, divided by the N rate applied.

^¥Full description is presented in Table 2.

^‡Determined by subtracting the cost of fertilizer from the gross income (grain yield due to N fertilizer application × price per unit grain).

^¥Full description is presented in Table 2.