[Effects of nitrogen supply level on microbial transformation of amino sugar in a mollisol amended with maize straw].

A 38-week laboratory incubation test at 25 degrees C was conducted to examine the effects of different inorganic N supply level (0, 60.3, 167.2, and 701.9 mg N x kg(-1) soil, noted as N0, Nlow, Nmid, and Nhig, respectively) on the microbial transformation of amino sugar in a mollisol amended with maize straw. Comparing with the control, the amendment of maize straw promoted the microbial synthesis of amino sugar, and at the early period of incubation, the total amount of soil amino sugar increased with increasing inorganic N supply, being significantly higher in treatments Nmid and Nhig than in treatments N0 and Nlow. With prolonged incubation time, the total amount of soil amino sugar decreased, and the decrement was higher in treatments N0 and Nlow than in treatments Nmid and Nhig. Different inorganic N supply level also had different effects on the dynamics of various amino sugars. Muramic acid exclusively originated from bacteria was more easily to be affected by the inorganic N supply, compared with the glucosamine from fungal cell wall residues. For the amendment of higher C/N maize straw, a sufficient N supply would be necessary for the promotion of the accumulation and transformation of soil amino sugar. Soil N deficiency would restrict the growth of soil microbes, weaken the microbial synthesis of amino sugar, and decrease the captured N in microbial biomass, being not beneficial to the soil N accumulation.