Nitrogen fertilizer management for subsurface drip-irrigated cotton

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Title: Nitrogen fertilizer management for subsurface drip-irrigated cotton
Author: Yabaji, Rajkumari
Abstract: Subsurface drip irrigation (SDI ) systems for cotton production greatly minimize water constraints , and nitrogen (N ) management becomes the main priority . Injecting N fertilizer into SDI systems should in theory be as efficient as is the irrigation delivery system . However , previous research by the Texas A &M University – Texas Agricultural Experiment Station Soil Fertility Program at Lubbock , TX has indicated that plant uptake of N fertilizer in SDI cotton is < 50 % of injected N . The research aims to improve N fertilizer management in SDI cotton . The research was conducted at Halfway , 2004 and Lubbock 2005 . 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 minimizing nitrification and denitrification losses . We also aimed to fine -tune the timing of N fertigation by comparing the fertilizer injection of both the sources of fertilizers from 15 June to 15 July and from 15 June to 30 July in 2004 at Halfway . At Lubbock we injected N fertilizer from 20 June to 22 July and from 20 June to 12 August . We also tested spectral reflectance -based timing of N fertigation from 20 June to 12 August at Lubbock , 2005 . Our results showed that lint yields with UAN plus ATS did not differ from UAN alone . Timing of N fertilizer injection 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 28 kg N ha -1 that was realized with the reflectance -based treatment (N rate was 72 kg N ha -1 ) relative to the other N -fertilized treatments , which received 102 kg N ha -1 Recovery efficiency of injected N averaged 63 % . In this study we also made direct measurements of denitrification using vented chambers and an acetylene inhibition method . We compared three treatments , control , soil NO3 - test -based UAN injection , and spectral reflectance -based UAN injection . Three chamber measurements were made in each plot . Samples were analyzed for N2O on a GC fitted with a PID detector . Denitrification fluxes in the SDI system were measurable , but not agronomically significant .
URI: http : / /hdl .handle .net /2346 /17248
Date: 2006-08

Citation

Nitrogen fertilizer management for subsurface drip-irrigated cotton. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /17248 .

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