外加营养源作用下微生物黏结剂对土壤团聚体的影响

通过室内培养实验研究了外加营养源条件下微生物黏结剂(真菌菌丝和微生物胞外多糖)对土壤稳定性的影响以及微生物在不同粒径团聚体中的分布.所加营养源分别为葡萄糖(以C计)和硝酸铵(以N计),实验周期为30 d.实验设计包括对照(0.5 mg.g-1)、CN5(0.5 mg.g-1,0.1 mg.g-1,C/N=5)、CN10(0.5 mg.g-1,0.05 mg.g-1,C/N=10)3个水平.结果表明,3个处理的土壤呼吸速率十分接近,最大值都在3.10 mg.(h.kg)-1左右,说明无机氮肥的施加短期内对葡萄糖的矿化作用不明显.除培养第5 d CK的大团聚体形成量(15.67%)显著低于CN5(25.32%)和CN10(24.63%)外,其余培养期间3个处理的团聚体含量总体无显著性差异,表明本实验中葡萄糖对微生物的影响较大,覆盖了施加无机氮的影响,从而导致团聚体含量之间差异不显著.

Impact of Microbial Aggregating Agents on Soil Aggregate Stability Under Addition of Exogenous Nutrients

In this study, we investigated the effects of biological aggregating agents (fungal hyphae and microbial extracellular polysaccharides) soil aggregate (with different sizes) stability under addition of exogenous nutrients. The exogenous nutrients included glucose and ammonium nitrate. Experiments were conducted in a 30 d incubation period with three treatments: 1 the control (0.5 mg·g^-1 soil); 2 CN5 (0.5 mg·g^-1 soil, 0.1 mg·g^-1 soil, C/N=5); 3 CN10 (0.5 mg·g^-1 soil, 0.05 mg·g^-1 soil, C/N=10). Results showed that soil respiration rates were not significantly different among the three treatments, with maximums being about 3.10 mg·(h·kg)^-1, indicating that the impact of inorganic nitrogen fertilizer was not obvious in a short term. Aside from 5 d, macroaggregates amount of CK (15.67%) was observably lower than those of CN5 (25.32%) and CN10 (24.63%), there were no remarkable discrepancies among 3 treatments in other incubation period. The insignificant difference in the aggregate amounts among the three treatments suggested that the influence of glucose on microbial activities surpassed the inorganic nitrogen fertilizer in short-term in the study.