Effect of Different Organic Materials on Nitrogen Mineralization in Two Purple Soils

Abstract

An aerobic incubation experiment was conducted at a constant temperature to investigate the differences in nitrogen mineralization between an acid purple soil and a calcareous purple soil amended with five 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). The results showed that the organic nitrogen forms in these materials followed the order of amino acid N> hydrolysable unidentified N> ammonium N> non-hydrolysable N> amino sugar N. Application of organic materials could significantly improve the contents of NH4⁺-N and NO3^--N in acid purple soil, PM and SC could significantly improve the content of NH4⁺-N, but 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, but decreased 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 was significantly and positively correlated with the contents of amino acid N and ammonium N, but 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 soil types and the characteristics of organic materials, especially the content of organic matter, C/N and the fractions of organic nitrogen in organic materials.