Impact of Long-term Use of Fertilizers and Manure on Distribution of Soil-inorganic Phosphorus Fractions in a Vertisol

The field experiment was conducted during the kharif season under the AICRP on Long-Term Fertilizer Experiment at the Research Farm, Department of Soil Science and Agricultural Chemistry, JNKVV, Jabalpur (M.P.), India. The investigation was carried out to assess the distribution of P fractions in Vertisol after the harvesting of the soybean crop. Eight treatments were imposed with four replications in a simple randomized block design. The treatments were applied in combination with different doses of fertilizer viz., T1 (50% NPK), T2 (100% NPK), T3 (150% NPK), T4 (100% N), T5 (100% NP), T6 (100% NPK+FYM), T7 (100% NPK-S), and T8 (control). Through the findings, the soil pH and electrical conductivity (dS m-1) did not show significant changes even after the long-term application of various fertilizer levels compared to their initial values. The treatment with 100% NPK + FYM exhibited the highest organic carbon (g kg-1) content and available N, P, and K (kg ha-1) content over the control. The various forms of phosphorus in the soil were observed in the following order: Ca-P > Fe-P > Al-P > Occluded-P > Saloid-P . The Ca-P content was highest when 100% NPK fertilizer and farmyard manure (FYM) were used together. The analysis showed that the presence of saloid-P significantly influences the availability of phosphorus in Vertisol soil. Based on the current investigation, it is recommended to use integrated nutrient management, which includes both 100% NPK fertilizer and FYM, to prevent phosphorus deficiency in soybean cultivation in Vertisol.