| With the rapid development of agriculture, the annual demand of nitrogen fertilizer has increased significantly. As organic material is rich in nitrogen, taking full of it could not only improve the recycling of nitrogen, avoid the waste of organic materials, but also an effective method to ease the development of nitrogen resources. The form of nitrogen varies with different kinds of organic materials and sources. Therefore, it is of great significance to make clearly the transformation of nitrogen in organic fertilizers in the soil in order to improve the utilization rate of nitrogen in organic materials and reduce the risk of nitrogen to environment.The southwest wide distribution of purple soil is taken as the research object, with five kinds of representive organic materials including biogas residues of pig manure(PM), cow manure(CW), sewage sludge compost(SC), rural waste compost(RWC1)and the compost of rural waste plus 20% of sewage sludge(RWC2). Organic nitrogen forms of the five kinds of organic materials are analized. An aerobic incubation experiment was conducted under a constant temperature to investigate the differences in nitrogen mineralization between an acid purple soil and a calcareous purple soil amended with different organic materials mentioned above. The corn pot experiment was conducted by taking the chemical fertilizer as reference. By researching the impact of organic materials ito nitrogen migration and transformation behavior and the availability in purple soils, this paper focuses on the clarification of the mechanism and influence factors, thus providing a theoretical basis for the rational application of organic materials.(1)The nitrogen morphological characteristics of organic materials showed that nitrogen is given priority to organic nitrogen in the organic material, forms in organic nitrogen of these materials followed the order of amino acid N > hydrolysable unidentified N>ammonium N>non-hydrolysable N>amino sugar N. The proportion of the same organic nitrogen fraction varies a lot among the different organic materials.(2) The laboratory incubation experiment results showed that applying organic materials could significantly increase MBC and MBN content in soils, while the CM and SC are most prominent, respectively. Application of organic materials could significantly improve the content of NH4+-N and NO3--N in acid purple soil, PM and SC could significantly improve the content of NH4+-N, while CM reduced the content of NO3--N in calcareous purple soil. Except for CM, which had no significant effect on the quantity of nitrogen mineralization in acid purple soil, lowered the quantity of nitrogen mineralization in calcareous purple soil, applying the organic materials could significantly increase the quantity of nitrogen mineralization in both soils. Correlation analysis showed that the quantity of nitrogen mineralization were significantly and positively correlated with the contents of amino acid N and ammonium N, while were significantly and negatively correlated with the content of organic matter and the C/N of organic materials. Overall, the results illustrated that the effect of organic materials on the mineralization of nitrogen varied with soils and the characteristics of organic materials, especially the content of organic matter, C/N and the fractions of organic nitrogen in organic materials.(3) The pot experiment results showed that application of fertilizer could improve total nitrogen and available nitrogen content in two purple soils, which indicates that the organic materials could improve the availability of soil nitrogen. Fertilizer nitrogen use efficiency was much higher compared with organic materials treatments with a circumstance of even mitrogen application. For organic materials treatments, SC maintained the highest nitrogen use efficiency, while CM the lowest. Under a same treatment, the utilization of nitrogen in the acid soil was higher than in the calcareous purple soil. |
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