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Summary of Cotton Yield Response to Foliar Applications of Potassium Nitrate and Urea

M. Wayne Ebelhar and Joe O. Ware


Potassium (K) deficiency symptoms have been observed in fast-fruiting, early- maturing cotton (Gossypium hirsutum L.) cultivars across the Cotton Belt. Research was conducted across the Cotton Belt to evaluate foliar K applications for increasing cotton lint production. Several factors including the interaction of foliar potassium nitrate (KNO3) and urea at different levels of soil-applied K were evaluated at various locations and many continue to be researched in some areas. In Mississippi, along with the Beltwide protocol, additional treatments were included in subsequent years to examine the interaction of plant growth regulators with foliar KNO3 and urea. The objectives of these studies were 1) to determine lint yield response to foliar KNO3 and urea with different levels of soil-applied K and 2) to evaluate the interaction of foliar KNO3 and urea applications with plant growth regulators (mepiquat chloride and PGR-IV). A 3-year study was conducted from 1991 to 1993 on a Dundee silt loam at the Delta Research and Extension Center at Stoneville, MS. Treatments included 0, 50, 75, and 100 lb K/A soil-applied with either foliar-applied KNO3 or urea. There were no significant yield difference with either foliar-applied KNO3 or urea in any of the three years. No K deficiencies were evident, and maturity was unaffected by treatment. In 1994, a 2-year study was begun to continue the evaluation of foliar K and also introduced plant growth regulators into the system. There was no significant interaction between the main effect factors (foliar-applied nutrients, mepiquat chloride and PGR-IV). When averaged across foliar systems, there was no significant lint yield increase with PGR-IV in either year. When averaged across years and foliar systems, mepiquat chloride increased lint yields by 4% (33 lb lint/A). The foliar systems had no significant effect on lint yield in either 1994 or 1995 but when averaged across years and plant growth regulators, both foliar-applied urea and foliar-applied KNO3 increased lint yields by 5 to 6% (47 and 42 lb lint/A, respectively).

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 683 - 688
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998