Plant Growth, Yield Components, Economic Responses, and Soil Indigenous K Uptake of Two Cotton Genotypes with Different K-Efficiencies

HG103, a high K-efficiency cotton cultivar with high-yield potential, and LG122, a low K-efficiency cotton cultivar with low-yield potential were used to study the genotypic variation on yield, economic responses, and soil indigenous K exploitation for cotton in pot and field conditions in 2006 and 2007. Results indicated that both the cultivars differed significantly in the rate of translocation of dry matter into reproductive organs and the time of running into reproductive stage. Cotton yield and economic parameters of HG103 were much better than LG122. Potassium content in cotton shells reached the highest level at maturity stage for both genotypes. Results also showed that the K content in each plant part of HG103 was lower than that of LG122. The two genotypes showed different efficiencies and abilities on absorbing soil rapidly available K and slowly available K. LG122 showed higher absorption of K rate than HG103 after K fertilization, but on the contrary, HG103 uptake more soil indigenous K than LG122 in no K fertilization treatment. This result indicated that HG103 could tolerant and absorb more soil indigenous K than LG122, under condition of soil K stress. LG122 could grow well and absorb more K nutrient when soil K supply is sufficient. Our results demonstrated that higher K content in plant tissues and higher K uptake by plant may not an exclusive condition for high yield planting with K fertilization. Earlier translocation of more dry matters into reproductive organs is one of the key mechanisms of high K use efficiency in cotton.