土壤微生物量和土壤固定态铵的变化及水稻对残留N的利用

在小麦盆栽试验后的^15N标记土壤上，研究了水稻生长过程中土壤微生物量C、N和土壤固定态铵的变化及其有机无机肥料残留N的有效性，结果表明，土壤微生物量C随着水稻生长而逐渐增加，到收获时达到1378．6－1790．5mg/kg土；土壤微生物量N的变化与水稻吸收N素有关，开始时由于淹水使得土壤微生物N有所下降，但随后又有所增加；随着水稻的N的吸收增加，生物量N又下降，直到水稻成熟期又有所恢复。在整个水稻生长季节中，土壤固定态铵的含量变化不大，但其中的一些^15N仍与外界土壤中矿质N发生了交换，表明 些固定态铵对水稻仍有较高的有效性。

CHANGES OF SOIL MICROBIAL BIOMASS N AND SOIL FIXED AMMONIUM DURING RICE GROWTH AND USE EFFICIENCY OF RESIDUAL N BY RICE

Pot experiments were carried out on the ¹⁵N-lablled soil after winter wheat to study the changes of soil microbial biomass C,N and soil fixed ammonium during rice growth. The results showed that soil microbial biomass C increased with the rice growing and reached the highest at the harvesting stage. The soil microbial biomass N decreased a little bit at the beginning of experiment and then rose to the highest at the tillering stage, after which it decreased again with the increase of N absorption by rice. The content of soil fixed ammonium changed little during the rice growing.some of the ¹⁵N fixed by soil clay minerals exchanged with the soil mineral N, showing that the fixed ammonium in last crop was also effective to rice at the second cropping.