Evaluation of Irrigation and Fertilization Strategies to Improve Irrigation and Nitrogen Water Use Efficiencies in Cotton

A three-year study was initiated at the University of Georgia’s Stripling Irrigation Research Park (SIRP) to evaluate a combination of irrigation and fertilization strategies to improve irrigation and nitrogen water use efficiencies in cotton.  The study has three fertilization strategies x three irrigation strategies for a total of nine treatments.  Each treatment has three replicates.  The study is conducted using a randomized block design with twenty-seven 48 x 48 ft plots.  The plots are irrigated with a VRI-enabled lateral-move irrigation system.  The three irrigation scheduling treatments are the SmartIrrigation Cotton App, soil water tension thresholds as measured by the University of Georgia Smart Sensor Array (UGA SSA), and the UGA Extension Checkbook or calendar method.  The three fertilization treatments are traditional (20 lb N/ac at planting and one 85 lb N/ac liquid side-dress application), fertigation (20 lb N/ac at planting, 85 lb N/ac in 3 fertigation events), and using NDVI to apply the Clemson algorithm for estimating the amount of liquid N applied at side-dress.  NDVI is calculated from reflectance measured with a UAV-mounted multispectral sensor.  Cotton was planted in a heavy rye residue using strip tillage.  Soil cores were collected in 6 in increments to 36 in prior to planting, four times during the growing season, and after harvest to quantify soil N.  Whole plant samples were collected four times during the growing season and segmented to quantify N concentrations within the plant.  This paper will present the results from the first year of the project and provide early conclusions on the performance of the nine treatments.