Effect of potassium application on yield and nutrient uptake by cotton

The present investigation was carried out in Vertisols of Akola district of Maharashtra to ascertain the effect of potassium application on yield and nutrient uptake by Bt Cotton. This was carried out by conducting field experiments on research farm of Department of Soil Science and Agricultural Chemistry, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola and similarly on five farmer`s fields in intensive cotton growing area of Vertisols in Akola district during 2012-13 and 2013-14. The treatments comprised of various levels of potassium (0, 25, 50 kg K2O ha-1) applied through either MOP or SOP and additional foliar sprays of SOP @1.5 per cent at critical growth stages of cotton along with addition of equivalent quantity of sulphur through bensulf and control without potassium. It has been observed that despite the soils having high soil available potassium, the application of potassium was found to have significant response and improved the yield of cotton. It was observed that the increasing levels of potassium caused significant increase in yield of cotton. The lowest cotton yield was recorded at control where only nitrogen and phosphorous was applied without any potassium application. Application of K2O @ 25 kg ha-1 under farmer`s practice further increased the yields of cotton. Application of 50 kg K2O ha-1 has further increased the yields statistically over control indicating that cotton has shown response to application of potassium in Vertisols. However, the source of potassium viz, MOP and SOP used in the present study did not record statistically significant difference in the seed cotton yield. The number of bolls per plant was increased along with increase in the levels of potassium from 0, 25 and 50 kg K2O ha-1. Significant increase in boll weight has been observed due to application of potassium and the increase in levels of potassium also leads to increase in boll weight of cotton. The application of potassium @ 50 kg K2O ha-1 either through MOP or SOP irrespective of sources showed highest seed cotton yield and nutrient uptake. The yield of cotton was increased along with the increasing levels of potassium indicating necessity of balance nutrition (NP and K) under Vertisols. The foliar application of SOP @1.5% at flowering and boll development stage was beneficial to enhance seed cotton yield. The study also suggests the necessity of inclusion of application of potassium in the fertilization of cotton grown on Vertisols for increasing productivity as well as increasing nutrient uptake by cotton besides maintaining soil fertility and to arrest mining of potassium in soils.