Nitrogen Mineralization Kinetics in some Tropical Soils Amended with Ashed and Un-ashed Animal Manures

This study is carried out to evaluate mineral nitrogen release of three animal manure ashes and dried animal manures by kinetic models under incubation, screen-house, and field conditions. Soils were treated with dried manures and manure ashes of cattle, goat, and poultry and NPK 15-15-15 at 120kg N ha^-1 after which the amended soil mixtures were taken fortnightly and analyzed for mineral nitrogen. The incorporation of manure ashes increased mineral N in the incubation experiment; there was a significant increase of 184%, 245%, 53%, and 65% in the screen-house and field experiments respectively with the cattle manure ash amendment compared to the control and dried manure. Mineral N release was in the following order: screen-house experiment incubation experiment field experiment. The first and second order was fit for N release only from the goat manure ash in the incubation and screen-house experiments. The relationship between N kinetics and time was polynomial.