Using UAVs and NDVI Readings to Predict Grower N Rates in North Carolina Cotton

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Virginia Tech

This research project was completed in conjunction with an ongoing research effort in Virginia cotton using remote sensing to predict nitrogen (N) application rates. It was conducted to provide additional N prescription data by Unmanned Aerial Vehicle (UAV) for Northeastern, North Carolina. The study was conducted in Scotland Neck, Halifax County, NC (36.1331597, -77.5026541). This county produces 95,000 bales during in 2021 (USDA NASS, 2022). As one of the largest acreage counties in NC, it was ideal for the UAV study and its algorithm creation. The objective was to determine if N rates prescribed by NDVI readings from a UAV flight resulted in improved and/or similar cotton yields than grower standard N rates in North Carolina and Virginia cotton. There were two treatments during the study with the first being the grower practice of N fertilization and the second being UAV determined N application rate at five weeks after planting (5WAP) with four replications of each treatment. The UAV was flown at 5WAP to determine N rates needed at lay-by/top dress. Nitrogen was applied at a grower standard rate of 92 lbs. N/acre on four control replications and at a UAV prescription rate of 114 lbs. N/acre on four test replications. Harvested acres were summed, bale weights were taken, and lint samples were collected time of harvest. The lint samples were micro-ginned at the Tidewater Research station in Suffolk, Virginia for lint percentage. Nitrogen prescription provided by UAV resulted in an 83 lbs. lint/acre increase over the grower standard, though not statistically different. At a 42.7% turnout, the grower standard N application resulted in a yield of 1,806 lbs. lint/acre and the UAV prescribed N resulted in a yield of 1,889 lbs. lint/acre. This trial will be used as part of a larger data set to encourage validation of UAV prescribed N.