秸秆还田对土壤氮素转化的影响

Effect of straw returning on soil nitrogen transformation

利用原状土柱田间培养法 ,测定了冬小麦、夏玉米农田土壤氮 (N)素的年净矿化量 ;利用氯仿熏蒸浸提茚三酮反应氮法测定了土壤微生物量氮的数量 ;利用连续流动分析仪测定了土壤表层无机氮的含量。结果表明 ,在冬小麦秸秆覆盖、夏玉米秸秆翻埋的土壤中 ,第 1年土壤氮净矿化量为N 2 10kg/hm2 ,第 2年为 179kg/hm2 ,2年的净矿化量均基本与同期施氮量相当。在秸秆不还田的土壤中 ,第 1年土壤氮净矿化量为N 16 4kg/hm2 ,第 2年为2 4 8kg/hm2 ,年际变化较大。翻埋玉米秸秆导致小麦季土壤表层无机氮数量增加 ,引发土壤氮矿化的正激发效应 ;表层覆盖小麦秸秆对玉米季土壤表层无机氮的影响不明显。秸秆还田后 ,每个生育期开始时 ,土壤微生物量氮比不还田土壤的增加 72 %～ 2 34% ,每个生育期结束时增加 34%～ 72 %。在实施秸秆还田的最初 2年内 ,土壤微生物量但氮处于动态调整阶段 。

The amount of soil nitrogen net mineralization in field cropped with winter wheat and summer maize was measured by in situ incubation method The soil microbial biomass nitrogen was measured by chloroform fumigation extraction and ninhydrin reactive nitrogen method The soil inorganic N was measured by continued flow analysis instrument In the soil covered with winter wheat straw in summer and incorporated with summer maize straw in autumn, the net N mineralization was 210kg/hm 2 in the first year, 179 kg/hm 2 in the second year The net mineralization was approximately equal to the amount of applied N In the non\|straw returning soil the net mineralization was 164 and 248 kg/hm 2 in the first and second year, respectively Incorporating maize straw to the soil resulted in increase of inorganic N during wheat season and positive effect of soil N mineralization Surfacing wheat straw in summer gave no significant difference in soil inorganic N The soil microbial biomass N in straw returning soil was 72～234% greater than that in the non\|straw returning at beginning of each season, and was 34～72% greater at ending of each season The soil microbial biomass N in straw returning soil alternate during the first 2 years and did not be stable at a new level