Potassium Supply Strategy for Enhancing Productivity and Nutrient Use Efficiency in FCV Tobacco grown in Northern Light Soils of Andhra Pradesh

Abstract

Flue Cured Virginia (FCV) tobacco, an important high value commercial crop in India, is preferentially grown on light textured soils for better quality and exports. However, light textured soils are characterized with low potassium (K) reserves, poor K retention and high vulnerability to K leaching. Of all the essential nutrients, K is taken up in the largest amount by tobacco grown in irrigated Northern Light Soils (NLS) region of Andhra Pradesh. The large requirement coupled with low efficiency of applied K calls for evolving a K supply strategy that ensures optimum K nutrition of the crop and enhances K use efficiency. A field investigation was carried out for two consecutive Rabi seasons to evaluate potassium supply strategies for their effects on productivity and nutrient use efficiency of irrigated FCV tobacco on a sandy loam soil (Alfisol). The experiment comprising eight K supply strategies varying in rate, number of splits and timing of K applications was laid out in a randomized block design with three replications. Results indicated that K application either at 120 or 80 kg K2O ha-1 led to significant increase in green leaf yield, cured leaf and grade index of FCV tobacco over the no-fertilizer control and NP fertilizer use alone. K application in 4 equal splits (1:1:1:1) at 10, 25, 40 and 70 days after transplanting (DAT) resulted in higher yields as compared to its addition in 3 splits (1:2:1) at 10, 25 and 40 DAT or 25, 40 and 70 DAT. Nutrient uptake and use efficiency by tobacco was promoted by K application in 4 splits in contrast to its addition in 3 splits. All plots receiving K application maintained higher K availability as compared to the control and minus-K plots. The soil K availability was more or less similar for 120 kg K2O-1 and 80 kg K2O-1 with the identical K application strategies. Over all, the K application in 4 splits (1:1:1:1) timed at 10, 25, 40 and 70 DAT is the right K supply strategy for higher productivity and enhanced K use efficiency in irrigated FCV tobacco grown on light textured soils.