Availability and dynamics of organic carbon and nitrogen indices in some soils amended with animal manures and ashes

Purpose The study evaluated dried manures and manure ashes as alternative products from animal manures, and determined the dynamics of soil nitrogen availability indices and organic carbon release in some soils amended with dried manures and ashes under laboratory incubation, screen-house and field experiments. Methods Cattle, goat and poultry manures were collected and air dried to produce dried manures after which part of the dried manures were burnt in open space at a temperature range of 320-450 degrees C to produce manure ashes. Treatments which were no amendment (control), dried manures of cattle, goat and poultry manure ashes of cattle, goat and poultry and NPK 15-1515 at 120 kg N ha(-1) were applied to soil. Samples were taken fortnightly after amendment incorporation in the incubation experiment; in screen-house experiment and field experiments, plant seeds were established after amendment incorporation; thereafter, soil samples were taken fortnightly. Soil samples were analyzed for soil organic carbon (SOC), NH4+-N and NO3--N using a spectrophotometer. Results Incineration of manures increased pH, exchangeable cations and carbon, while nitrogen in manures ashes was comparable to nitrogen in dried manures. The application of manure ash increased SOC, NH4+-N and NO3--N by 182, 102, 128% in incubation experiment while 64 and 628% increase in SOC and NH4+-N was recorded in screen-house experiment, respectively, relative to the control. In the field experiment, a significant increase in NO3--N was recorded at the onset of incorporation; nitrification was more pronounced than ammonification under incubation and field conditions. Conclusion Dried manures are not superior to manure ashes and incorporation of manures ashes increased the SOC, NH4+-N and NO3--N though changes with increasing weeks were erratic.