Interrelationships of Yields with Canopy NDVI, Plant Height, and Leaf Nitrogen

Innovative nitrogen (N) management systems and practices that can manage N more efficiently are needed to increase grower profitability due to substantially increased N prices and tighter environmental regulations during the last several years. The objectives of this study were to 1) determine the optimal N fertilizer application rates and timings for high-yielding cotton production systems in Tennessee; and 2) investigate the relationships among lint yield, canopy normalized difference vegetation index (NDVI), plant height, and leaf N concentration at key growing stages. A field trial was conducted at Jackson and Milan, TN from 2008 to 2009. Five N application rates of 0, 40, 80, 120, 160, and 200 lb N/acre and two N application timings (at plant, and between first square and first bloom) were evaluated in field plots (12.7 ft × 30 ft) in a randomized complete block design with four replicates. The following measurements were taken on an individual plot basis: Soil nitrate before cotton planting and after harvest; canopy NDVI readings, plant height, and leaf N concentrations at the beginning of bloom, mid of bloom, and the end of bloom; and lint yield at harvest. Relationships among lint yield, NDVI, crop N, and plant height were determined using different regression models.