Nutrient Release Pattern and Soil Enzyme Activities of Calcareous Soil as Influenced by Phosphate Rich Organic Manure

A study was conducted at Post Graduate Laboratory, Division of Soil Science, College of Agriculture, Pune to study the nutrient release pattern and soil enzyme activities of calcareous soil as influenced by various levels of phosphorus using organic and inorganic sources. The experiment was conducted in randomized block design with seven treatments replicated three times. The treatments comprised as T1- Absolute control, T2 - RDF (50:75:45 N: P2O5:K2O kg ha-1) through DAP, T3 - RDF (50:75:45 N: P2O5: K2O kg ha-1) through SSP, T4- 25 % P2O5 through PROM, T5- 50% P2O5 through PROM, T6 -75% P2O5 through PROM and T7 -100% P2O5 through PROM and RDF of soybean was used for incubation. The study demonstrated that applying 100% P2O5through Phosphate Rich Organic Manure (PROM) significantly improved soil poperties, by reducing soil pH and calcium carbonate, increasing organic carbon, and enhancing the availability of macronutrients (nitrogen, phosphorus, potassium) and micronutrients (iron, manganese, zinc, copper). Enzyme activities, including urease, dehydrogenase and alkaline phosphatase were improved in calcareous soils, correlating positively with nutrient availability, particularly with phosphorus and micronutrients such as iron and manganese. PROM application was more effective than chemical fertilizers in promoting nutrient mobilization and improving soil enzyme activity over a 120-day incubation period. Strong correlations were observed between enzyme activity and micronutrient availability, especially in treatments receiving 100% P2O5through PROM, indicating its potential to enhance both nutrient cycling and soil fertility.