Impact of NPK Fertilizer Levels on Soil Properties and Potassium Fractions in Lateritic Soil of Coastal Maharashtra

An investigation was carried out in cluster bean during the Rabi season of 2021-2022 in the lateritic soil of coastal Maharashtra to assess the changes in soil properties, potassium (K) balance and K content as influenced by different fertilizer doses. The experiment involved nine treatments that were replicated three times in a randomized block design. The findings demonstrated that application of 40:60:60 NPK (kg ha-1) significantly enhanced availability of K in soil i.e., exchangeable K (85.70 mg kg-1) as well as non-exchangeable K (243.44 mg kg-1), whereas highest water-soluble K (5.12 mg kg-1), lattice K (4862.26 mg kg-1) and total K (5183.00 mg kg-1) was observed with 60:40:60 NPK (kg ha-1) fertilizer dose. The dominance sequence of the various K fractions was as follows: total K > lattice K > non-exchangeable K > available K > exchangeable K > water-soluble K. The results showed that available nitrogen, phosphorus, and potassium had a positive and significant relationship with organic carbon. The results indicated that applying balanced potassic fertilizers can improve the chemical properties of soil. Moreover, highly significant and positive correlations have been noted between water-soluble, exchangeable, non-exchangeable, lattice and total K, suggesting dynamic equilibrium among the different fractions of K. The application of 40:60:60::N:P2O5:K2O (kg ha-1) proved to be most helpful in enhancing K fractions in lateritic soil of the coastal region of Maharashtra, considering the most available potassium forms as well as improvement in the availability of nutrients.