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Effect of N Rate and Placement on No-Tillage Cotton

D.D. Howard


Information on nitrogen (N) application methods for no-tillage (NT) cotton production is limited. Research was initiated on a Loring silt loam at the Milan Experiment Station in 1994. The experimental design was a RCB with treatments replicated five times. N rates of 0, 30, 60, 90, and 120 lb/A were broadcast, injected, and split applied to NT cotton. The cultivar 'D&PL 50' was planted by mid-April in 4 row (40 inches) by 30 feet plots. Surface residues were old cotton stalks and spring killed weeds. The broadcast and injected N rates were applied immediately after planting. The split rate plots were fertilized with 60 lb/A N at planting with 30 and 60 lbs/A N applied a month later. Plots were fertilized with 40 lb/A P2O5, and 60 lb/A K2O, using 0-46-0 and 0-0-60. Ammonium nitrate was the broadcast N source and UAN the injected N source.

Two year average NT cotton lint yields were increased by increasing the N rate. Yields were unaffected by method of application. A year-by-N rate interaction affected lint yields. In 1994, yields were increased with N through the 120 lb/A rate. Yields in 1994 were excellent in relation to 1995. The 1995 yields were increased with N through the 60 lb/A rate and were reduced by applying 120 lbs/A. Yields were unaffected by different application methods. The advantage of injection application method is to apply the N sources below surface residues reducing immobilization. This research indicates that surface residues on these plots were insufficient to immobilization sufficient N to reduce yields. As would be expected responses to the higher N rates occurred during a year of greatest yield. This research will be continued evaluating NT cotton produced on either small grain or corn residues.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 1394 - 1395
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998