Variable-rate nitrogen fertilization of winter wheat under high spatial resolution

• Published in: Precision agriculture 2018-06, Vol.19 (3), p.570-587
• Main Authors: Stamatiadis, S., Schepers, J. S., Evangelou, E., Tsadilas, C., Glampedakis, A., Glampedakis, M., Dercas, N., Spyropoulos, N., Dalezios, N. R., Eskridge, K.
• Format: Article
• Language: English
• Subjects: Agricultural practices; Agricultural production; Agriculture; Atmospheric Sciences; Biomedical and Life Sciences; Chemistry and Earth Sciences; Computer Science; Crop yield; Crops; Data processing; Economics; Environmental impact; Farmers; Fertilization; Fertilizers; Grain; Leaching; Life Sciences; Nitrogen; Performance assessment; Physics; Precipitation; Profitability; Remote Sensing/Photogrammetry; Seasons; Sensors; Signal processing; Soil analysis; Soil Science & Conservation; Soil water; Spatial data; Spatial discrimination; Spatial resolution; Statistics for Engineering; Triticum aestivum; Water balance; Wheat; Winter; Winter wheat
• ISSN: 1385-2256; 1573-1618
• DOI: 10.1007/s11119-017-9540-7

Variable-rate application (VRA) addresses in-field variation in soil nitrogen (N) availability and crop response, and as such is a tool for more effective site-specific management. This study assessed the performance of a VRA system for on-the-go delivery of granular fertilizer in 7-m wide and 200-m long strips of a 2.4-ha wheat field. A randomized complete block design consisted of three treatment strips (a preplant uniform application of 100 kg N/ha, a preplant + in-season uniform farmer rate of 212 kg N/ha and a preplant + in-season VRA) within four blocks. The VRA prototype consisted of Crop Circle ACS-430 active canopy sensors, a GeoScout X data logger that processed the geospatial data to convey a real-time N rate signal (1 Hz) to a Gandy Orbit Air 66FSC spreader through a Raven SCS 660 controller. Crop monitoring included analysis of in-season soil and plant samples, water balance and grain yield. VRA delivered an economic optimum N rate using 72% less in-season N or 38% less total N (131 kg N/ha) than that applied by the farmer (212 kg N/ha). The reduction of total N inputs came about without any yield losses and translated to 58% N-use efficiency in comparison to 44% of the farmer practice and 52% of the preplant control. VRA also provided a much higher revenue over fertilizer costs, €68/ha and €118/ha higher than the preplant control and the farmer practice, respectively. The return of VRA per unit of N was equal to that of the large preplant application due to low leaching losses. Overall, the high-resolution VRA was superior in terms of environmental benefits and profitability with the least uncertainty to the farmer.