The release of nitrogen (N) from slow release N fertilizers (SRNF) is affected by soil microbial activity. However, several studies have shown variable results regarding the effect of microbial population size on the release of nutrient from slow release fertilizers. To understand this relationship clearly, changes in activities of two soil enzymes (urease and dehydrogenase), microbial population and available macronutrients viz nitrogen (N), phosphorus (P) and potassium (K) were assessed in an incubation study conducted under ambient condition. The six treatments were used for present investigation as control, 100% urea and crotonylidene diurea (CDU) @ 100, 75, 50 and 25% of recommended dose. The results indicated that the addition of N through commercially available urea and CDU as per general recommended dose of nutrients (GRDN) showed an increase in soil enzyme activity, microbial population, available N, P and K. The urease enzyme activity was found to be highest of nutrients in GRDN treatment at 60 days after addition (DAA) (39.55 μg NH4+-N/g soil/hr) and in 100% N through CDU (37.45 μg NH4+-N/g soil/hr) at 90 DAA. The soil dehydrogenase enzyme activity was significantly higher in GRDN at 7, 14, 21 and 30 DAA (1.32, 1.44, 1.56 and 1.68 μg TPF/g soil/hr, respectively). However, at 60 and 90 DAA the dehydrogenase enzyme activity was significantly higher in 100% N through CDU (1.89 and 1.63 μg TPF/g soil/hr, respectively). The soil available N content increased up to 60 DAA in all the treatments and it was significantly higher in GRDN followed by 100% N through CDU. However, it was significantly higher at all the periods of incubation over 75, 50, 25 and 100% N through CDU.

SummaryA field experiment was conducted at Post Graduate Institute, Mahatma Phule Krishi Vidyapeeth Rahuri, dist-Ahmednagar ( M.S.) with raw and post bio-methanated spent wash for preparation of bio-compost from the different organic sources like press mud cake, baggasse, sugarcane trash, farm waste like pearl millet straw, chickpea straw and wheat cut straw etc. and seasonal sugarcane crop (Saccharum officinarum) variety Co 86032 was planted with sixteen treatments, three replications in sodic soil. Absolute control, farm yard manure and vermicompost treatments were taken for comparison with bio-composts. The growth parameters like height of the plant, girth of the stem, number of tillers etc. as well as yield , quality of sugarcane and soil chemical properties etc. were found significantly higher in the post bio-methanated biocompost treatment as compared to the raw spent wash bio-compost treatment under sodic soil condition.

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