Potassium Nutrition in Cotton: Genotypes, Boll Load, and Root Growth

L.D. Janes, D.M. Oosterhuis, F.M. Bourland, and R.W. McNew


The effects of foliar-applied potassium nitrate (KNO3) on cotton (Gossypium hirsutum L.) yields, lint quality, and K distribution in the plant have been documented at the University of Arkansas, but genotypic effects are not well understood. A field study was conducted in 1991, 1992 and 1993 at two locations in Arkansas to determine the effect of foliar-applied KNO3 on seed cotton yield, Verticillium wilt, root growth and K distribution in plants of six genotypes with widely differing maturities. Potassium nitrate was foliarly applied at 10 kg ha-1 at 2, 4, 6, and 8 weeks after the first-white-flower stage of growth. The experimental design was a randomized complete block with split plot and six replications. Foliar K was split within the genotype, and the high and low boll loads were further split within the K applications. Plant samples were collected from 1m of row at pin-head square, first flower, and 5 and 9 weeks after first flower. Growth analysis of the samples included total leaf area, plant height, number of main-stem nodes, plant dry weight with percentage K recorded for each plant component, and seedcotton. The foliar-K treatment tended to increase the K content for all cultivars, but not significantly. Root growth of different genotypes decreased during boll development but the relationship with K demand was not clear. In 1991 and 1993, there were no significant increases in yield from the foliar-applied KNO3, and no significant differences among cultivars. In 1992, foliar application of KNO3 significantly increased seedcotton yield in one cultivar. The plant growth showed no significant difference between foliar K and no foliar K treatments. Foliar-applied K tended to increased the total dry weight of all cultivars, but not significantly. Results indicated there were no consistent genotypic responses to foliar feeding with K. Boll load appeared to influence plant response to foliar K fertilization. This work will be continued in 1994 with emphasis on root growth and plant K requirements.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 1374
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998