淹水土壤中秸秆氮素的转化

Transformation of Straw ^(15)N in the Submerged Soil

采用15N示踪技术和密闭培养法研究水稻和玉米秸秆15N在淹水土壤中的转化过程。结果表明 :土壤中秸秆15N的各转化过程相互制约 ,每个过程中15N含量都处于动态变化之中。秸秆种类和土壤类型对土壤矿质15N含量的影响随时间延长逐渐变小 ,培养 112d后土壤中矿质15N含量仅占加入秸秆15N的 0 96 %～ 1 6 8%。秸秆15N有 2 0 3%～ 4 2 5 %被微生物固持 ,0 2 3%～ 14 16 %被粘土矿物固定。粘土矿物类型影响土壤对秸秆15N的固定 ,变性土中固定态15NH+ 4含量明显高于红壤。秸秆15N的固定使其以气态形式损失的量减少 ,这在农业生产中将有助于保持土壤肥力。整个培养过程中秸秆15N的损失率为 2 9 70 %～ 46 30 %。 112d后秸秆15N实际矿化了 47 72 %～5 1 74% ,仍有 5 0 %左右的秸秆15N残留于土壤。

N labelled rice straw and maize straw were used to study the transformation of 15 N in submerged soil by using 15 N tracer technique and sealed incubation method.Each transformation process of straw 15 N in submerged soil conditioned each other,and content of straw 15 N in each process was in a dynamic state.Effects of plant varieties and soil types on soil mineralized 15 N decreased gradually with the extension of incubation time.After 112 days incubation,soil mineralized 15 N only accounted for 0 96%～1 31% of straw 15 N added to soils About 2 03%～4 25% of straw 15 N was immobilized by microbial and 0 23%～14 16% of which was fixed by clay minerals.Types of clay minerals could affect content of fixed 15 N in soils.In this study vertisol fixed much more straw 15 N than ultisol did.Obviously,the immobilization of straw 15 N decreased its loss in the form of gas,which could be beneficial to maintain soil fertility in agricultural practice.During the whole incubation,loss rate of straw 15 N ranged from 29 70% to 46 30%.After 112 days incubation straw 15 N actually mineralized 47 72%～51 74%,namely half of which still remained in the soil.