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Nitrification Inhibitor Evaluation on Cotton. II. Inhibitor Incorporation Depth and N Placement

York, A. C., Tucker, M. R.
Agronomy journal 1985 v.77 no.3 pp. 407-411
Gossypium hirsutum, nitrogen fertilizers, nitrification inhibitors, North Carolina
The use of nitrification inhibitors (NIs) in the Southeast has given inconsistent results. Because application techniques may afTect the efficacy of NIs, a 3-year experiment with cotton (Gossypium hirsutum L.) was conducted on a sandy, low organic matter soil (Arenic Paleudults) to evaluate the efficacy of etridiazol [5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole] and nitrapyrin [2-chloro-6-(trichlorometlyl) pyridine] when N was broadcast and deeply incorporated or applied as a 36-cm band over the row surface. The NIs, tankmixed with trifluralin (α,α,α-trifluor0-2,6-dinitro-N,N-dipropyl-p-to-luidine) herbicide, were deeply incorporated with a disk prior to bed formation or shallowly incorporated with a rolling cultivar after bed formation. Regardless of N placement method or NI incorporation depth, neither inhibitor affected cotton yield, percent lint, fiber quality, or leaf N, P, K, Ca, Mg, Fe, Mn, Zn, Cu, or B contents. Split N applications, with one-third at planting and the remainder sidedressed at the early square stage, increased N-use efficiency in 2 of 3 years. Nitrogen placement did not affect cotton yield, fiber quality, or leaf nutrient content. Surface-banding the N reduced stands by 9 to 20%. As compared to shallow incorporation, deep incorporation of trifluralin reduced cotton yield 6 to 17% and leaf K content at the peak flowering stage 7 to 24%, but did not affect fiber quality. Deep incorporation of trifluralin, combined with either surface-banded N or application of all N at planting, reduced cotton stands in 2 of 3 years.