Using Active Canopy Sensing to Adjust Nitrogen Application Rate in Corn
2012
Barker, D. W. | Sawyer, J. E.
Remote sensing that uses active sensors continue to be tested as an N stress detection method and provide in-season rate adjustments to corn (Zea mays L.). The objectives of the study were to use active canopy sensing to vary in-season N application at the V10 corn growth stage and compare applied N rate, grain yield, and nitrogen use efficiency (NUE) with N applied before planting. A fertilizer N rate study was conducted in 2009 and 2010 near Ames, IA. Pre-plant N rates were 0 to 270 kg N ha⁻¹ and then sensor-based rates were applied in-season at the V10 corn growth stage. Rainfall events occurred 3 to 5 d after N application each year, providing corn response to the in-season applied N and increasing relative corn canopy biomass by the V13 growth stage. The pre-plant applied nitrogen (PP-N) 270 kg N ha⁻¹ rate used as the N-reference did not result in the highest green normalized difference vegetative index (GNDVI) or produce the highest grain yields. The pre-plant plus sensor applied nitrogen (PP+S-N) recovered corn yield from plant N stress at V10. The best yield recovery with deficit pre-plant N and sensor-directed N application rate occurred each year when no pre-plant N had been applied. Overall, economic optimum nitrogen rate (EONR) and NUE in PP-N and PP+S-N were the same. The PP+S-N application does give corn growers options for addressing in-season N deficiency and protect yield potential when corn N need is uncertain or when soil N losses are unavoidable.
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