Tuesday, November 14, 2006 - 8:00 AM
191-1
Spectral Reflectance Based Nitrogen Management for Subsurface Drip Irrigated Cotton.
Subsurface drip irrigation (SDI) systems for cotton production greatly minimizes water constraints, and nitrogen management becomes the main priority. Injecting N fertilizer into SDI systems should in theory be as efficient as the irrigation delivery system itself is. However, previous research by the Texas A&M University – Texas Agric. Exp., Stn. Soil Fertility Program at Lubbock, TX has indicated that plant uptake of N fertilizer in SDI cotton is < 50 % of injected N. This research aims to improve N fertilizer management in SDI cotton. We tested two fluid N fertilizer sources: urea ammonium nitrate (UAN) vis a vis UAN plus ammonium thiosulfate (ATS). The ATS source theoretically acts as an N stabilizer against nitrification and denitrification losses. We also aimed to fine-tune the timing of N fertigation by comparing UAN injection from 20 June to 22 July with UAN injection from 20 June to 12 August. Finally, we tested spectral reflectance-based timing of N fertigation from 20 June to 12 August. Our results showed that lint yields with UAN plus ATS did not differ from UAN alone. Timing of N fertilizer injection also did not affect lint yields. Lint yield with the reflectance-based treatment was not significantly different from yields with the other N-fertilized treatments. The most encouraging result of this study was the savings of 25 lb N/ac that was realized with the reflectance-based treatment (N rate was 65 lb N/ac) relative to the other N-fertilized treatments, which received 90 lb N/ac. Recovery efficiency of injected N averaged 63%. Second year results will be presented.
Recorded presentation