| Using 15N labeled organic manure and urea, a pot experiment was conducted to investigate the effect of organic and inorganic fertilizer on nitrogen（N） pool and distribution of residual N fractions in fluvo-aquic soil under the winter wheat system. The results shown：（1）The effect of organic fertilizer on soil total N was significantly（P<0.05）：Soil total N increased by 24.8%, ammonium N and nitrate N of which increased by 59.0% and 120 times respectively in OM* treatment（application of 15N labeled pig manure totally）; soil total N increased by 13.7%, nitrate N of which increased by 84.5 times in OM*+CF treatment（application of 15N-labeled pig manure with common urea）; the effect on the content of soil total N, nitrate N and ammonium N was not significantly performed in CF* treatment（application of 15N labeled urea only）. （2）Compared to the non-fertilizer（CK） treatment, the application of N fertilizer increased the contents of different fractions of organic N in soil, especially the contents of hydrolysable organic N and hydrolysable ammonium N in OM* treatment were significantly increased by 25.3% and 39.3%, respectively（P<0.05）, the proportion of organic forms accounted for total N was in dynamic balance.（3）The contribution of exogenous nitrogen to the nitrogen contents in different fractions varied with fertilizer forms. The content of hydrolysable ammonium N and non hydrolysable N was significantly influenced by the application of the chemical fertilizer respectively, and the content of non-hydrolysable N and hydrolysable unidentified N by the application of the organic fertilizer significantly, and the content of hydrolysable unidentified N by the application of the organic fertilizer significantly.（4）As the transformation of exogenous inorganic nitrogen, 27% of soil ammonium N and nitrate N respectively, derived from the application of chemical fertilizer in CF* treatment, and as that of exogenous organic nitrogen, 8% and 5% from the application of organic fertilizer in OM* and OM*+CF treatment respectively.（5）Ammonium N and nitrate N, hydrolysable ammonium N and hydrolysable unidentified N were available N; the present results indicated that the chemical fertilizer combined with organic fertilizer is a practical approach for promoting the transformation and distribution of organic fertilizer to available N, increasing the availability of organic fertilizer, reducing environmental risk and maintaining the sustainability of soil. |
