Response of leaf characteristics of BT cotton plants to ratio of nitrogen, phosphorus, and potassium

Application of nitrogen (N), phosphorous (P) and potassium (K) is an important practice for cotton (Gossypium hirsutum L.) production and is a useful tool to enhance cotton plant growth and physiological activities, especially during boll setting and boll development. This study investigated the effects of the ratio of N, P, and K on physiological parameters of leaves during boll development using Bacillus thuringiensis (Bt) cotton cultivars Siza 1 and Sikang 1. As compared with the treatment without P and K application, combined application of N, P and K significantly increased chlorophyll a content by 5.7% and 14.6%, chlorophyll b content by 22.6% and 3.8%, carotenoids content by 14.7% and 9.9%, soluble proteins by 0.6% and 17.5% as well as soluble sugar by 16.8% and 7.9% in the two growing seasons. Similarly, catalase was enhanced by 10.0% and 14.6%, peroxidase by 45.5% and 47.5%, superoxide dismutase contents by 4.9% and 42.2%, and seed cotton yield by 29.2% and 18.7%, respectively. Our study indicated that combined application of N, P, and K at appropriate ratios enhanced the activity of physiological parameters and yield and the ratio of 1:0.6:0.9 considerably performed best for Sikang 1 cultivar amongst all treatments. (author)