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Nitrification Inhibitor Evaluation on Cotton. I. Rate and Time of N Application

York, A. C., Tucker, M. R.
Agronomy journal 1985 v.77 no.3 pp. 403-406
coastal plains, fertilizer application, Gossypium hirsutum, nitrification inhibitors, nitrogen, North Carolina
Most cotton (Gossypium hirsutum L.) in the southeastern USA is grown on sandy soils that are subject to extensive N leaching. Split applications of N are normally utilized to reduce leaching losses. Even with split applications, however, leaching can still subject the crop to periods of N deficiency which can lead to yield reductions. Experiments were conducted at three sites (Typic and Plinthic Palendults soils) in 3 years to determine if at-planting application of a nitrification inhibitor (NI), either etridiazol [5-ethoxy-3-(trichloromethyl)-l,2,4-thiadiazole] or nitrapyrin [2-chloro-6-(trichloromethyljpyridine], would allow for reduced N application rates and/or eliminate the need for split N applications. Urea was incorporated at three rates (65,100, and 135 or 45,90, and 135 kg N ha⁻¹), either all applied at planting or as a split application with 22 kg N ha⁻¹ at planting and the remainder sidedressed at the early square stage. Etridiazol or nitrapyrin, each at 0.56 kg ha,⁻¹ was incorporated with the at-planting urea. Leaf N content at the early square and peak flowering stages, stand counts, lint yield, and fiber length and micronaire were recorded. Neither NI affected lint yield, fiber length, or micronaire. Etridiazol reduced stands 6% and increased leaf N content 9% at the early square stage at one of three sites. Nitrogen application rates and N application time did not affect fiber length or micronaire. Increasing N application rates reduced stands when all N was applied at planting. Yield response to N application rates and N application time varied by location and appeared to be related to rainfall patterns and N carryover from previous crops. Neither NI affected crop response to N application rates or N application time.