Effect of water deficit and soil-applied potassium on partitioning and the efficiency of foliar-applied potassium in cotton

Information has been lacking about whether K deficiency, water-deficit stress, and foliar-applied K interact to affect K partitioning, physiological processes, and growth in cotton (Gossypium hirsutum L.), which are integral to the development of seedcotton yield and fiber quality. It was hypothesized that reported inconsistent yield responses to soil- and foliar-applied K fertilizers could be related to water-deficit stress, which affects physiological processes, partitioning of K, and plant growth. Field studies were conducted in 1999--2002 using eight treatment combinations of well-watered or dryland conditions, high or low soil K, and with or without foliar-applied K arranged in a split-split plot design with five to six replications.;Across site-years, lint yield increased 6.2% due to soil-applied K under irrigated conditions but no increase was observed under dryland conditions. Across site-years, foliar-applied K increased lint yield most under low soil-K (5.1%) and under dryland (7.3%) conditions. Foliar-applied K increased lint yield primarily by increasing the weight of bolls, particularly in dryland plots. Foliar-applied K increased the number of seeds per hectare; however, the response was not affected by water-deficit stress. Climatic variation between seasons governed the degree to which lint yield and components of yield responded to water-deficit stress.;Soil-applied K and water-deficit stress did not consistently affect fiber quality. Fiber length and uniformity were increased by foliar-applied K irrespective of the soil K and water treatments. Water-deficit stress increased fiber micronaire but decreased fiber elongation response to foliar-applied K. Foliar-applied K increased low-canopy fiber elongation, mid-canopy fiber elongation and micronaire, and upper-canopy fiber elongation, and micronaire irrespective of the soil K and water levels. Soil-K level, water level and site-year factors regulated the response of low-canopy fiber strength, and upper-canopy fiber length to foliar-applied K. Soil-applied K increased low-canopy fiber elongation, mid-canopy fiber uniformity, and upper-canopy fiber uniformity irrespective of the water level. Observations across multiple site-years supported our hypothesis that the fiber quality response of cotton to soil and foliar-applied K fertilizers can be related to water-deficit stress in Arkansas.;Concentrations of glucose, fructose, and sucrose in leaves were reduced by foliar-applied K in low-soil K plots under water-deficit but not well-watered conditions. Foliar-applied K increased chlorophyll and ATP production in leaves irrespective of the water and soil-K treatments. (Abstract shortened by UMI.)...