Department of Plant Sciences

Potassium (K) efficiency and physiological mechanisms of two cotton cultivars (Gossypium hirsutum L.) were studied in 2007 using a pot experiment at different K levels (-K and +K). The results showed significant differences in K efficiency between the two genotypes (Genotype 103, a high K efficiency and high yield potential genotype; and genotype 122, a low K efficiency and low yield potential genotype). Genotype 103 had higher boll numbers, lower boll shed rate and higher lint yield. The lint yield of genotype 103 was 1.83 times that of genotype 122 at ＋K treatment, and 2.57 times that of genotype 122 at －K treatment. However, K concentrations in different parts of genotype 103 were lower than that in genotype 122. This suggests that genotype 103 maintained its normal physiological function with low K concentration. Genotype 122 showed poor growth with higher K concentration in the tissues yet lower ability to absorb and utilize soil K. In both genotypes, K application significantly increased fiber uniformity, strength, length and micronaire. At same K level, genotype 103 had higher lint percent and moderate fiber length, length uniformity, strength, elongation and micronaire, whereas genotype 122 had higher fiber length, micronaire and moderate lint percent, length uniformity, strength, and lower elongation.