淹水培养对土壤微生物生物量形成与肥料氮转化的影响

SOIL MICROBIAL BIOMASS FORMATION AND FERTILIZER N TRANSFORMATION UNDER SUBMERGED CONDITIONS

研究室内培养条件下水稻秸秆配施化肥氮对土壤微生物生物量的形成和氮素转化的影响。８４ｍｇＮ／ｋｇ标记硫铵和４．５ｇ／ｋｇ稻草粉配施淹水培养，结果表明，有２５．８％的肥料氮在培养６３ｄ时成为生物量及其代谢产物－１５Ｎ。整个培养过程中生物量－１５Ｎ无净再矿化现象。将稻草粉换成葡萄糖淹水培养，葡萄糖在培养７ｄ时消耗贻尽，此时生物量－１５Ｎ达最大值４３．１ｍｇＮ／ｋｇ，相当于施入肥料氮的５１．３％。在此条件下，生物量－１５Ｎ有明显净再矿化现象，且净矿化出来的氮遭受损失。稻草粉处理好气培养结果表明，新形成的生物量及其代谢产物－１５Ｎ较淹水培养处理高得多，达４７．０ｍｇＮ／ｋｇ，相当于施入肥料氮的４６．３％。在此条件下，生物量－１５Ｎ亦无明显净再矿化现象。比较不同处理的氮素回收率。

A laboratory incubation experiment was conducted to study the effect of rice straw incorporation on soil biomass formation and fertilizer N transformation under submerged conditions. 84mg N/kg of 15 N labelled ammonium sulphate and 4.5g/kg powdered mature rice straw were co incorporated. Results showed that biomass and associated metabolites 15 N continuously increased during incubation, reaching 27.4mg N/kg by the end of incubation, equivalent to 25.8% of the added labelled N. There was no net remineralization of biomass N observed during the incubation. When rice straw was substituted by glucose (at the rate of 4.8g/kg), glucose was decomposed rapidly. No glucose was remained in the soils by 7 days incubation. The maximum of newly formed biomass 15 N was 43.1mg N/kg, equivalent to 51.3% of added labelled N. There was obvious net remineralization of biomass 15 N after 7 days incubation. The recovery showed that the remineralized 15 N was subject to loss during the succesive incubation. When the straw treated soils were incubated aerobically, the newly formed biomass 15 N was higher than that in submerged conditions, being 47.1mg N/kg by 63 days incubation, which was equivalent to 46.4% of added labelled N. Comparing the recoveries from straw and non straw treatments, it was concluded that straw incorporation could reduce fertilizer N loss.