RESPONSE OF COTTON GROWTH AND PRODUCTIVITY TO APPLICATION OF POTASSIUM AND ZINC UNDER NORMAL AND LATE SOWING DATES

Abstract

Two field experiments were carried out in Sakha Agric. Res. Sta., Kafr El-Sheikh Governorate, Egypt during two growing seasons (2007 and 2008) using the Egyptian cotton cultivar Giza 86 (G. barbadense, L.), to study the response of cotton growth and productivity to application of potassium and zinc under two planting dates. The experimental design was split-plot with four replications. The main-plots were assigned to two planting dates, i.e., normal planting date on March 30th and late planting date on April 30th. The sub-plots included six potassium and zinc fertilization treatments i.e., two soil application levels (24 and 48 kg K2O/fed.) alone or with the foliar application of zinc at the level of 0.5 g Zn SO4/liter. Potassium was also tried as foliar application at the level of 5 kg K2SO4/fed. alone or with the abovementioned level of zinc. Soil added potassium was applied at thinning, while foliar added one was partly sprayed at the beginning of flowering and two weeks later. Zinc was sprayed once at beginning of flowering. The results indicated that sowing date gave significant effects on all growth parameters; no. of open bolls/plant, boll weight, no. of plants/fed. at harvest, seed index and seed cotton yield/fed., upper half mean length, micronaire reading, reflectance and yellowness in favour of early planting. Sowing date did not exhibit any significant on lint %, uniformity index, fiber strength and fiber elongation % in both seasons. Foliar application of potassium along with the foliar application of zinc gave a significant increase in plant height at harvest, no. of nodes/plant, no. of sympodia/plant, no. of open bolls/plant, boll weight, seed index and seed cotton yield (ken./fed.) as compared with the other fertilization treatments. The efficiency use of heat units by cotton plants increased in favour of normal sowing rather than in late sowings. The foliar application of potassium and zinc treatments did not exhibit any significant effect on all fiber quality traits in both seasons. It could be concluded that the foliar application of 5 Kg K2SO4/fed. sprayed partly twice + foliar application of 0.5 g ZnSO4/L once at beginning of flowering stage could be recommended to increase the yield and its components under normal or late sowing dates., for Giza 86 variety, under Sakha region condition at Kafr El-Sheikh Governorate.