Correlation of Methanotrophs and Soil Enzymes with Available Nutrients in Long Term Green Manured Rice Rhizospheric Soil

The indiscriminate use of chemical fertilizers in agriculture decreases the soil fertility as well as soil health and their adverse effects are clearly visible on soil microflora, soil function and structure. This scenario necessitates the need to adopt the integrated organic farming which maintains the soil health and sustainability. So, the present study was conducted during kharif season 2013 at Department of Microbiology and Agronomy, Punjab Agricultural University, Punjab, India to assess the effect of green manure application along with variations in plant density on methanotrophic populations, soil enzymatic activity and their correlation with available nutrient status of the soil. Highest methanotrophic population (176×105 cfu/g) was observed in the treatment having green manure (15 t/ha) + 44 plants/m2 + recommended NPK at 90 DAT. The highest soil dehydrogenase (50 µg Triphenyl formazon/g soil/hr) and urease activity (855 µg/g soil/h) was found in the treatment having green manure (15 t/ha) + 33 plants/m2 + recommended NPK whereas, alkaline phosphatase (21.9 µg p-nitro phenol/g soil/h) were observed in the treatment having green manure+ 44 plants/m2 + recommended NPK. A highly significant positive correlation was observed between methanotrophs and available nutrient content in soil. Similarly, the soil enzymatic activities were also positively correlated with the soil nutrients and organic carbon in soil. The study suggested that application of green manure along with increased plant density improves the soil health and fertility hence, increases the sustainability of cropping system.