Variable Rate Nitrogen Application in Corn Fields Applied with Manure
Peter Anthony
The number of farmers applying manure to corn fields is increasing. However, how to manage nitrogen (N) in such fields is very challenging, due to the uneven distribution of manure applied and the variability in nutrient content and availability during the growing season. What is more challenging is when cover crops are also planted in such fields. Little has been reported on the within-field variability in optimal sidedress N rates and the potential of variable rate sidedress N application in corn fields that have received manure applications with/without cover crops.
The overall goal of this project is to conduct on farm trials in commercial corn fields receiving manure applications with/without cover crops to evaluate the potential benefits of variable rate N application in Minnesota. On-farm N rate trials will be conducted in three fields at the Anthony Farms in St. Peter each year. Five different N rates (specific rates to be determined according to each field’s situation) will be applied at V8-V9 in two fields (one with manure and cover crops, the other with manure but no cover crops), and each field will be delineated into grids of 66 ft wide and 150-200 ft long. One grid will have one N rate, and four grids next to each other covering the four N rates form a block. The treatments will be randomly arranged in each block and the block will be replicated across each field. In the third field with manure and cover crops, the remote sensing and calibration strip-based precision N management technology developed will be evaluated using strip trials replicated across the field. PlanetScope satellite remote sensing images will be used to monitor corn growth conditions before and after variable rate sidedress N applications. Geospatial analysis will be performed to determine within-field variability in soil N supplies (from manure, residual soil N, soil organic matter mineralization, and/or cover crops), optimal sidedress N rates, and the potential benefits of variable rate N sidedress application in comparison with uniform N application or no N application.
The results of this project will provide important guidelines for precision N management of corn in fields with manure application and/or cover crops in Minnesota.
