秸秆还田对土壤氮素转化的影响
Effect of straw returning on soil nitrogen transformation
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摘要: 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 210kg/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 164kg/hm2,第 2年为248kg/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 ,尚未达到新的稳定状态Abstract: 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/hm2 in the first year, 179 kg/hm2 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/hm2 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