Potassium Balance under Soybean–wheat Cropping System in a 44 Year Old Long Term Fertilizer Experiment on a Vertisol
Priyanka Pathariya, B.S. Dwivedi, Ajay Kumar Dwivedi, Risikesh Thakur, Muneshwar Singh, S. Sarvade
Abstract
Applications of fertilizers alone and in combination with organic manure significantly increased the organic carbon, available nitrogen, phosphorous, potassium, and K fractions, i.e., water soluble-K, exchangeable-K, non-exchangeable-K, lattice-K, and total-K in both surface and subsurface soils and without K input (100% NP & 100% N). Among the various K fractions, lattice K was the dominant K fraction. The highest values of these fractions were found in 100% NPK + 5 t FYM ha−1. The relative contents of these fractions were in order, lattice-K > non-exchangeable K > exchangeable K > water soluble K, and these were higher in surface than the subsurface soils. Correlation studies revealed significant positive relationship of organic carbon and available N, P, and K with different K fractions in surface and subsurface soils. Furthermore, the minimum depletion of the K rate was recorded in 100% NPK + FYM (−2.25 kg ha−1 yr−1) to that of other treatments, while control showed a maximum K depletion rate (−3.86 kg ha−1 yr−1). Apparent K balance in soil was the lowest, −61 kg ha−1 yr−1, in control plot followed by −165 kg ha−1 yr−1 in the treatment of 100% NPK + FYM. Hence, much attention is required for potassium fertilizers to maintain the K status of soil and to prevent K mining.