Assessment of Quality of Different Organic Manures used by the Farmers of Khurda District in Orissa and their Effect on Microbial Activity of an Acid Soil

A laboratory incubation study was conducted to assess the effect of four common organic manures (cattle manure, poultry manure, goat manure and vermicompost) used by the farmers of Khurda district on an acid soil which constitutes more than 70% of the total cultivable area of Orissa state. Each of the manures was applied at two levels (5 and 10 g kg⁻¹) to a light textured (sandy loam) acid soil (pH= 5.5) collected from a well-drained medium land of Bhubaneswar and incubated for 4 weeks. The organic manures were also characterised with respect to some physical, chemical and biological parameters like moisture content, bulk density, pH, EC, C/N ratio, nutrient content and microbial properties. Weekly sampling of the incubated soil was done to measure changes in some microbial properties. It was observed that all the three animal manures contained more moisture than the standard range of 20–25%. With less moisture (16.4%), vermicompost was relatively dry. Poultry manure and goat manure were more aggregated and porous than the cattle manure and vermicompost. Except the goat manure, all other manures had alkaline pH (7.8–8.7), poultry manure was most alkaline with pH 8.7. Goat manure with wider C/N ratio (28.5:1) appeared to be immature as compared to cattle manure, poultry manure and vermicompost. Among the manures, poultry manure was biologically most active followed by cattle manure and goat manure. Both fungal and bacterial populations were very sensitive to organic manure application in acid soil and the degree of response varied with the type of organic amendment. Among the manures, poultry manure maintained highest level of dehydrogenase activity for a longer period followed by goat and cattle manures. Poultry manure also sustained highest phosphatase activity followed by goat manure at the end of 1^st week and cattle manure at the end of 2^nd week. Manure incorporation into the soil not only yielded higher microbial activity but also maintained it for a longer period. Poultry manure and goat manure were superior to both cattle manure and vermicompost in many characteristics.