无机氮素加入量对玉米秸秆分解过程中棕壤氨基糖含量的影响

作物秸秆还田作为一种调控土壤养分循环、减少氮肥损失、维持和提高土壤有机质水平的有力措施,越来越受到人们的重视1-2]。还田的秸秆是微生物的碳源和能源,常导致土壤微生物量迅速增加,相应的微生物死亡率和微生物残体积累量也提高3-4]。根据Appuhn等5]对微生物细胞壁组分的

Effects of inorganic nitrogen application rate on content of amino sugars in Alfisol during microbial decomposition of corn stalks

A 38-week incubation experiment (25°C) was conducted to investigate the effects of different inorganic N addition levels (0, 60.3, 167.2, and 701.9 mg•N•kg-1soil, denoted as N0, Nlow, Nmed, and Nhigh, respectively) on microbial formation and stabilization of heterogeneous amino sugars during the corn residue decomposition in an Alfisol amended with corn residues. Soil amino sugar content was determined by a gas-chromatography (GC) method. Soil samples were incubated with temperature kept at 25°C and soil moisture at 20% of air-dried soil basis. The amendment of corn residues significantly promoted the accumulation of microbial-derived amino sugars compared with the control. The total amount of soil amino sugar increased with increasing inorganic N addition rates, being markedly higher in Nmed and Nhigh than in Nlow and N0. Different inorganic N addition level also influenced the dynamics of individual amino sugars. Muramic acid exclusively originating from bacteria was more sensitive to inorganic N addition and exhibited a faster turnover rate, compared with the glucosamine from fungal cell wall residues. However, glucosamine and galactosamine gradually accumulated and stabilized with time in soil and they contributed more to the long-term maintenance of SOM. The result indicates that when plant residues with a large C/N ratio are incorporated into soil, sufficient N supply is necessary for accelerating transformation and accumulation of amino sugars in soil organic matter, i.e, enhancing the ability of microbial community to sequester N and/or C in their residues. However, high application rates of inorganic N were not necessarily assimilated by the soil microorganisms, and they could result in mineral N accumulation in soil. Therefore, the use efficiency of available N should be considered into account when crop residues were incorporated into soil after grain harvest in the field.