33-1 Active Canopy Sensing and Soil Nitrogen Content for Corn Nitrogen Management in Minnesota.

See more from this Division: ASA Section: Agronomic Production Systems
See more from this Session: Sensor Based Nutrient Management (includes student competition)

Monday, November 7, 2016: 8:00 AM
Phoenix Convention Center North, Room 126 B

Gabriel Dias Paiao, Minnesota, University of Minnesota, Roseville, MN, Fabian G. Fernandez, Dept. of Soil Water and Climate, University of Minnesota, St Paul, MN, Daniel E. Kaiser, Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN and Jared A. Spackman, Dept. of Soil Water and Climate, University of Minnesota, Lauderdale, MN
Abstract:

Active canopy sensors have been proposed as a tool to improve corn (Zea mays L.) nitrogen (N) management, but little has been done to improve sensor’s performance using soil N content. The objectives of this study are to compare the effectiveness of various canopy sensing tools and to evaluate the usefulness of soil N content to improve sensor’s predictive power to estimate grain yield and determine in-season N needs. Six to seven N rates at 35 to 45 kg urea-N ha-1 increments were pre-plant applied in 12 sites throughout Minnesota. Canopy sensing measurements were obtained at V4, V8, V12 and R1 development stages with SPAD, RapidSCAN (RS-NDVI/RS-NDRE) and GreenSeeker (GS-NDVI) and soil (0-30 and 30-60 cm) ammonium- and nitrate-N concentration at V4. Grain yield was determined at harvest. Regardless of the tool, sensing at V4 resulted in poor predictive power for grain yield and N needs. GS-NDVI and RS-NDVI were outperformed by the SPAD meter and RS-NDRE at all the sensing stages. The SPAD meter presented consistent predictive power from V8 to R1 with mean R2 values ranging from 0.62 to 0.70 for yield prediction and from 0.57 to 0.60 for in-season N rate predictions. Sensing at V12 with RS-NDRE provided the highest predictive power for grain yield (R2=0.82) and N needs, with slight underestimations of the N requirements (2 Kg N ha-1) and a sensor relative critical value of 0.99. The 0-30 cm soil nitrate concentration was as good, or better, than any other combination of ammonium, nitrate, and soil depth at improving sensor-based estimations of grain yield and in-season N needs. Soil nitrate as a covariate was especially useful early in development (V4) where yield prediction with RS-NDRE improved from R2 of 0.37 to 0.70 and N rate prediction improved from R2 of 0.22 to 0.75.  The combination of canopy sensing and soil N status hold promise to improve corn N management.

See more from this Division: ASA Section: Agronomic Production Systems
See more from this Session: Sensor Based Nutrient Management (includes student competition)

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