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Cotton Response to Foliar Applied Urea and Triazone Nitrogen in South Texas

B.W. Wallace, F.M. Hons, R.P. Wiedenfeld


Upland cotton (Gossypium hirsutum) requires adequate nitrogen for optimum yields. One method of supplementing soil applied nitrogen is through foliar application. Foliar applications of urea nitrogen have been tried for many years across the cotton belt, but response has been highly variable. No published information has been available regarding nitrogen status indicators for irrigated cotton grown in the Rio Grande Valley of Texas. This study investigated various indicators of cotton N status and response to foliar applied N. Foliar N fertilizers investigated were urea and triazone, a relatively new product originally marketed by Triazone Division Arcadian Corporation for which little information is available for cotton. Studies were conducted for three years at Weslaco, Texas in a factorial treatment arrangement with four levels of soil applied N and three foliar treatments, none, triazone, and urea. In two of the three years, foliar applied urea resulted in a significant increase in seedcotton yield in the absence of soil applied N. There were no other significant differences due to foliar treatment. Foliar applied triazone N was ineffective at increasing seedcotton yields. The trend in all years indicated that foliar applied urea increased yield when plants were N deficient, with the yield increment diminishing as plants approached N sufficiency. Petiole nitrate-N agreed well with established models, but indicated that current models may be slightly low during the prebloom and early bloom period for irrigated cotton in the Rio Grande Valley. Total leaf N indicated that 3.5% N represented a deficient level at any time during the bloom period, and that optimum levels may be closer to 4.0% N. Nodes above white flower (NAWF), height to node ratio, and portable chlorophyll meter readings (SPAD) appeared to have very limited usefulness as N status indicators for this region.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 1361 - 1366
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998