Continuous Cropping, Fertilization, and Organic Manure Application Effects on Potassium in an Alfisol under Arid Conditions

Effects of continuous cropping and addition of organic manures (farmyard manure, FYM, and groundnut shells, GNS) along with inorganic fertilizers on nonexchangeable potassium (K) release kinetics in a K-deficient Alfisol were studied in a 20-year manurial experiment under arid conditions. There was a depletion in available K under continuous cropping without K input (control) as compared to other treatments such as 100% nitrogen-phosphorus-potassium (NPK), 50% NPK + 4 metric tons (MT) groundnut shells ha-1, 50% NPK + 4 MT FYM ha-1, and 100% organic (i.e., 5 MT FYM ha-1). Over 20 years of cropping without K input, available K was reduced from 155 kg ha-1 (in 1985) to 82 kg ha-1 (in 2005), showing a negative balance of 73 kg ha-1. Soil in control plots showed available K in the deficient range (