Gutstein, Y.

The ability of Acala-type cotton cultivars to respond to soil-K of different levels of availability and to 0 - 1050 kg soil-applied and 2 kg foliar-applied potassium sulfate per ha, was investigated in field experiments at three locations. The reproductive yield and fiber characteristics revealed an obvious cultivar differential response ability to different levels of soil-K availability. Acala 1517 C, compared with A.4-42, possesses a very restricted ability of response to low-available soil-K (ΔF=-4159 cal. M-1); however, its ability improves and even exceeds that of A.4-42 at high levels of availability (ΔF=-2920 cal. M-1). The two cultivars also responded differentially to potassium sulfate applied to a poor K-reserve soil type; A.1517 C responded to an exclusively higher fertilizer rate range than A.4-42. Foliar-applied K had a slight effect (A.4-42), was ineffective or even negatively affected reproductive yield (A.1517 C), at low initial soil-K availability. However, significantly positive responses to this method of application were obtained with both cultivars at an initial relatively high K-availability. In this condition, the yield effect of 2 kg foliar-applied potassium sulfate per ha equaled (A.4-42) or even exceeded (A.1517 C) that of 350 kg per ha of soil-applied fertilizer. The differential cultivar ability to take up low available-K also expressed itself in a more pronounced detrimental effect on the fiber characteristics of A.1517 C, than on those of A.4-42. K-application improved all fiber properties tested, in particular fineness, maturity and strength. K decreased fineness by up to 33% in A.1517 C and up to 6.2% in the easy K-cropper A.4-42, and balanced off the very pronounced opposite effects of nitrogen and phosphorus on this characteristic. © 1972 Dr. W. Junk N.V.