Fractions of Soil Potassium and their Depthwise Distribution under Long-Term Nutrient Management Practices in Semiarid Alfisols in India

A field experiment was conducted on a long-term experimental plot during two consecutive rabi seasons of 2016-17 and 2017-18 at the college farm, College of Agriculture, Rajendranagar, Hyderabad, PJTSAU. The experimental soil was non-saline, neutral in reaction with sandy loam texture. Different forms of soil potassium were studied with six different nutrient management practices in randomized block design with four replications. The results of pooled data of two years study revealed that significantly higher contents of water soluble potassium (17.77 mg kg-1), exchangeable potassium (568 mg kg-1), nonexchangeable potassium (999 mg kg-1) and Total potassium (1.80%) in surface layer (0-15 cm) at flowering were recorded with integrated application of 50% N through FYM and 50% N through chemical fertilizers and it was on par with treatment applied 100% RDF through chemical fertilisers and significantly superior over other organic nutrient management treatments. A similar trend was observed at all soil depths (15-30, 30-45, 45-60 cm) and all the contents were decreased from flowering to harvest. All potassium forms decreased with increasing the depth except non exchangeable K. All the fractions were found to be significant in surface layer (0-15 cm). The contribution of different forms of soil K to Total K was in the order of non-exchangeable K> exchangeable K> water soluble K and similar trend was observed in all soil layers.