Variable Rate Nitrogen Application in Cotton Using Commercially Available Satellite and Aircraft Imagery.

The majority of the cotton farmers in the Texas High Plains use the nitrogen (N) application rate advised by researchers for this region, which is about 50 lbs N/acre for each bale anticipated at harvest.  With an expected yield of around 2 bales/acre, this would indicate an application rate of 100 lbs N/acre.  This is split into two applications of 50 lbs/acre before planting, and 50 lbs/acre at around two months after planting.  The objective of this study was to develop procedures for variable rate N side dress application in irrigated cotton fields based on multispectral satellite or aircraft imagery.  This study was carried out in cooperation with Brosch Farms near Slaton, Texas. Our focus this year was to establish N side-dressing recommendations based on remotely sensed estimates of crop ground cover (GC) made in the fields around 2 months after planting (an initial blanket N application was made before planting).  The experimental design was a randomized block design with split plots.  The main plot treatments were the different GC zones and the subplots were assigned three N treatments (0, 30 and 60lbs N/acre). In Stage 2 of the project (planned for next year), the previously developed N recommendations will be used to establish variable-rate N application prescriptions that will be used on the entire fields based on remote sensing imagery.  The result of this study will be a practical, cost-effective methodology for farmers and crop consultants to use variable-rate N fertilization in cotton.