Effects of Soil and Foliar Potassium Fertilizer Application on Cotton of Varied Maturity

For improving potassium fertilizer management of irrigated öcotton, the effects of foliar, and soil potassium appliction on two cotton culivars from 2004 to 2008 growing seasion in Zaradid soil series (silt loam soil) in Roudasht Agricultural Experiment Station (32o, 35' N, 52o, 20' E; 1420 m elevation) in Esfahan Province was studied. The experiment was a randomized complete block, with factorial split plot arrangement, with four replicates. The main plots were factorial combination of two cotton cultivars of different maturity (Varamin an intermediate, and B557 a relaviely short seasion cultivar) and foliar appliction of potasium and water, and the subplots were appliction of 0, 150 and 300 kg ha-1 K2O as potasium solfate. The initail available soil potassium during the experimental years was ranging from 200 to 300 mg kg-1 by amonium aceetate mehod. The results shows that the effect of foliar and soil potassium application on seed-cotton yield is relatively small due to initially high soil potassium level. The averaged four years seed-cotton yield, was 3085, kg ha-1. The average maximum annuall seed cotton-yield of Varamin and B557 cultivar (3462 and 2997 kg ha-1) were obtained by combined soil appliction of 150 kg ha-1 K2O, and foliar potasium appliction. The averaged minimum annual seed-cotton yield of Varamin (3082 kg ha-1) were obtained from combined soil application of 300 kg ha-1 K2O, and foiliar potassium application, and for B557 cultivar (2789 kg ha-1) without any soil and foliar potassium application, respectively. The effect of year on seed-cooton yield was significnt due to the annual and seasional fluctuation of irigation water salanity (ranging from less than 2 dS m-1 to greater than 10 dS m-1). The effect of folair potassium application on seed-cotton yield was not significant however; in three out of four years the seed-cotton yield in foliar potassium treatment was higher than foilar water treatment. In every 2 years of 4 years experiment soil application of 300 kg ha-1 potassium and no application of potassium resulted in the lowest seed-cotton yield. During four years of study, the averge highest seed-cotton yield for both caltivars were obtained from combind soil application of 150 kg ha-1 K2O and folair potasium application treatment. Comparing seed-cotton yield in potasium and none-potasium treatemts combined soil (150 kg ha-1 K2O) and foliar application of potassium is recommended