Optimizing nitrogen management for soft red winter wheat yield, grain protein, and grain quality using precision agriculture and remote sensing techniques

The purpose of this research was to improve the management of soft red winter wheat (Triticum aestivum L.) in North Carolina. There were three issues addressed; the quality of the grain as affected by delayed harvest, explaining grain protein variability through nitrogen (N) management, and developing N recommendations at growth stage (GS) 30 using aerial color infrared (CIR) photography.; The impact of delayed harvest on grain yield, test weight, grain protein, and 20 milling and baking quality parameters was studied in three trials in 2002 and three trials in 2003. Yield was significantly reduced in three out of five trials due to dry, warm environments, possibly indicating shattering. Test weights were significantly reduced in five out of six trials and were positively correlated to the number of precipitation events and to the number of days between harvests, indicating the negative effects of wetting and drying cycles. Grain protein was not affected by delayed harvest. Of the 20 quality parameters investigated, flour falling number, clear flour, and farinograph breakdown times were significantly reduced due to delayed harvest, while grain deoxynivalenol (DON) levels increased with a delayed harvest.; Grain protein content in soft red winter wheat is highly variable across years and environments. A second study examined the effects of different nitrogen (N) fertilizer rates and times of application on grain protein variability. Seven different environments were utilized in this study. Though environment contributed about 23% of grain protein variability, the majority of that variability (52%) was attributed to N management. It was found that as grain protein levels increased at higher N rates, so did overall protein variability as indicated by the three stability indexes employed. In addition, applying the majority of total N at growth stage (GS) 30 decreased grain protein stability.; Site-specific N management systems using remote sensing techniques can potentially improve nitrogen use efficiency (NUE) in winter wheat. The objectives of the last study were to determine if in-season agronomic optimum N rate recommendations in soft red winter wheat at growth state (GS) 30 could be developed using spectral bands and indexes obtained from aerial color infrared (CIR) photography and to determine if and how biomass at GS 30 affected these relationships. (Abstract shortened by UMI.)...