Seasonal Changes in Estimated Nitrogen Response in Winter Wheat (Triticum aestivum L.)

Abstract

In 2014 246,618,023 ha of wheat was harvested around the world where wheat made up roughly 8% of land area where crop cultivation is possible. Nitrogen use efficiency (NUE) for cereal crop production is near 33% which can be improved to help with production costs and to diminish potential offsite losses of nitrogen (N) fertilizer. The objective of this work was to use sequential NDVI measurements from two long-term nutrient management experiments to illustrate growth changes over the life cycle with NDVI, known to be a good indicator of total plant biomass. A further evaluation of the response index (RI) of N over one cropping cycle in winter wheat was performed. The RI was determined by dividing the NDVI from the high N rate plot by the NDVI from the 0-N check plot (RI NDVI). Sensor NDVI readings were collected weekly for three months. This approach was hoped to expand our knowledge of mapping wheat growth stages using sequential NDVI data. definitive differences in RINDVI were observed over time, and that peaked for Experiment 222, but less so for Experiment 502 where at lower N rates (< = 90 kg N ha-1); this peak tended to occur, when 120 days from planting to sensing, where growth was possible, had occurred. For Experiment 502, declining slopes for RI’s over time, computed with lower N rates, suggests that N in the soil system was being depleted and that the rates were clearly not sufficient to provide for plant demand for N mid to later season. Compared to results of past studies the maximum NDVI’s collected were lower, which could be due to a poor plant stand or planting.