Adjusting midseason nitrogen rate using a sensor-based optimization algorithm to increase use efficiency in corn

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.