Effect of Potassium Application Methods on Antioxidant Enzyme Activities, Yield, and Potassium Use Efficiency of Cotton

With application of modern cotton (Gossyium hirsutum L.) varieties including Bt (Bacillus thuringiensis) transgenic cotton, premature senescence caused by potassium (K) deficiency has become an important problem in cotton production in the Yellow River Valley of China. Field trials were conducted in 2009 and 2010 using Lumianyan 28. Four treatments consisting of no potassium (CK), basal application of potassium sulfate (T1), split application (1/2 basal dressing and 1/2 top-dressing at blossom-ing and boll forming stage) of potassium sulfate (T2), basal application of controlled-released compound fertilizers (T3) were designed. The same amount of potassium was applied with 150 kg K2O ha–1 in each fertilizer treatment. The results indicated that application of potassium significantly increased chlorophyll and soluble protein contents, superoxide dismutase (SOD) and cata-lase (CAT) activities (at the leaf ages of 30, 40, and 60 days), seed cotton yield and lint yield, as compared with CK. Moreover, application of potassium produced significantly lower malondialdehyde (MDA) content and peoxidase (POD) activity (at the leaf ages of 30 and 45 days), as compared with CK. Split application (1/2 basal dressing and 1/2 top-dressing at blossoming and boll forming stage) of potassium sulfate significantly increased soluble protein content (at the leaf ages of 30, 40, and 60 days), SOD (at the leaf ages of 15, 30, and 45 days) and CAT (at the leaf ages of 15 and 30 days) activities, seed cotton yield, lint yield and potassium use efficiency, and produced significantly lower MDA content (at the leaf ages of 30, 45, and 60 days) and POD acti- vity (at the leaf age of 30 days), as compared with basal application of potassium sulfate and controlled-released compound ferti- lizers, respectively. As far as high yield and high efficiency concerned in the experiment, the most appropriate potassium fertiliza-tion for recommendation is treatment T2 with split application (1/2 basal dressing and 1/2 top-dressing at blossoming and boll forming stage) of potassium sulfate.