Simplified and Advanced Sentinel-2-Based Precision Nitrogen Management of Wheat

This study compares simplified and advanced precision nitrogen (N) fertilization approaches for winter wheat relying on Sentinel-2 NDVI, grain yield maps, and protein content. Five N fertilization treatments were compared: (1) a standard rate, calculated by a typical N balance (Flat-N); (2) a variable rate calculated using a simplified linear model, adopting a proportional strategy (NDVI directly related) (Var-N-dir); (3) a variable rate calculated using a simplified linear model, adopting a compensative strategy (NDVI inversely related) (Var-N-inv); (4) a variable rate calculated using the AgroSat model (Var-N-Agrosat); and (5) a variable rate calculated applying the Agricolus model (Var-N-Agricolus). The study was carried out in four fields over two cropping seasons with a randomized blocks design. Results indicate that the weather remains the main factor influencing yield, as it typically happens in a rainfed crop. No substantial differences in crop yield were observed among the N fertilization models within each year and experimental location. However, in the more favorable season, the low-input direct model (Var-N-dir) resulted as the best choice, providing the higher NUE (nitrogen use efficiency) value. In the less favorable season, results showed a better performance of the advanced models (Var-N-Agricolus and Var-N-Agrosat), which limited yield losses and reduced intra-field variability, with relevant importance given to the increasing frequency of abnormal climate phenomena. In general, all these VRT approaches allowed reduction of the excess of fertilizers, preservation of the environment, and saving money.

Automated summary

This study compared simplified and advanced precision nitrogen fertilization approaches for winter wheat using Sentinel-2 NDVI, grain yield maps, and protein content. Five N fertilization treatments were evaluated, with results indicating that weather was the main factor influencing yield. While no substantial differences in crop yield were observed among the N fertilization models within each year and experimental location, the low-input direct model (Var-N-dir) yielded the highest nitrogen use efficiency in more favorable seasons, while the advanced models (Var-N-Agricolus and Var-N-Agrosat) performed better in less favorable seasons. Overall, all these variable rate technology (VRT) approaches allowed for reduced excess fertilizers, environmental preservation, and cost savings.