BACKGROUND: To investigate mineralization characteristics of organic resources in the soil, comprising five materials (rice straw, cow manure sawdust compost, microorganism compost, mixed oil-cake, and amino acid fertilizer), were treated according to the nitrogen content, and an indoor incubation experiment was conducted for 128 days. The results of this analysis were applied to determine the nitrogen mineralization pattern of these organic resources.
METHODS AND RESULTS: During the constant temperature incubation period, the nitrogen net mineralization rate of the organic resources was the highest in the amino acid fertilizer with the highest nitrogen content and lowest in rice straw with the lowest nitrogen content. A positive correlation (0.96) was observed between the potential nitrogen mineralization rate and total nitrogen content. The mineralization rate constant, k, was negatively correlated with the organic matter(-0.96) and carbon content(-0.97). The nitrogen mineralization rate during the first cropping season, as estimated by the model, was 6.6%, 11.6%, 30.9%, 70.7%, and 81.0% for rice straw, cow manure sawdust compost, microorganism compost, mixed oil-cake, and amino acid fertilizer, respectively.
CONCLUSION: The nitrogen mineralization rate varies depending on the type of organic resources or the nitrogen content; thus, it can be used as an index for determining the nitrogen supply characteristics of the organic resource. Organic resources such as compost with low nitrogen content or those undergoing fermentation contain organic nitrogen. Organic nitrogen is stabilized during the composting process. Therefore, as the nitrogen mineralization rate of these resources is lower than that of non-fermented organic resources, it is desirable to use these to improve soil physical properties rather than to supply nutrients when the amount of applied fertilizer is determined.