Predicting Optimal Nitrogen Rate Using NDVI and Uav's in the Upper Southeast Coastal Plain

A study was initiated in 2020 at three locations in Virginia to evaluate the using of normalized difference vegetative index (NDVI) in the Upper Southeast Coastal Plain cotton growing regions. The objective of the study was to evaluate handheld and UAV mounted cameras which measure NDVI at various days after planting and predict the optimum N application at side-dress to maximize lint yield. The study measured NDVI at 5, 6 and 7 weeks after planting (WAP) with a Trimble Handheld Greenseeker® and Micasense Altum® multispectral camera mount on a UAV platform. A modified algorithm from Clemson University was used to predict the optimum side-dress N application rates which were applied at 8 WAP. Cotton petiole nitrate-N samples were collected during the 1^st week of bloom as an in-season indicator of N status and to ensure that predict side-dress N rates were optimum. The NDVI measurements were also used to develop a NDVI growth curve model that will then be supplemented into the prediction algorithm for optimum N application rate. Initial results were that the algorithm from Clemson over estimated optimum N application due to early season growth and lagging NDVI. A NDVI growth curve for the Upper Southeast Coastal Plain is needed to more finely tune the algorithm for this region.