Losses and Transformations of Nitrogen at Low Value of C/N Ratio Compost

Abstract The aim of this work was to study the transformations of nitrogen at lower value of C/N ratio (15) for co-composting pig manure with leaves and rice straw. A series of parameters such as pH, electrical conductivity (EC), ash contents, moisture contents, seed germination index (GI), and different nitrogen forms were monitored. The accumulative organic matter losses followed a first-order kinetic function in both piles, and the co-composting of pig manure with rice straw had a higher mineral rate constant. The concentration of ammonium nitrogen released during composting was higher in the co-compost of rice straw and pig manure, as a result, the total nitrogen losses by ammonia volatilization was higher. The concentration of ammonium nitrogen was correlated with the degradation of organic nitrogen and the moisture content. The increases of nitrate nitrogen were not observed in both piles in the thermophilic phase due to the high temperature and high concentration of ammonium nitrogen which could inhibit the activity and growth of nitrifying bacteria. Total nitrogen losses in the first two weeks were high as a strong emission of ammonia and the increase of the pH value during thermophilic phase in both piles. But the total nitrogen losses in the mature compost were low due to the mass loss of the compost, high height of compost layer and high moisture content. C/N ratio increased during the thermophilic phase then decreased to 10.14 and 8.48 at the end of composting.