有机物料输入稻田提高土壤微生物碳氮及可溶性有机碳氮

土壤微生物量碳、氮和可溶性有机碳、氮是土壤碳、氮库中最活跃的组分，是反应土壤被干扰程度的重要灵敏性指标，通过设置相同有机碳施用量下不同有机物料处理的田间试验，研究了有机物料添加下土壤微生物量碳（soil microbial biomass carbon，MBC）、氮（soil microbial biomass nitrogen，MBN）和可溶性有机碳（dissolved organic carbon，DOC）、氮（dissolved organic nitrogen，DON）的变化特征及相互关系。结果表明化肥和生物碳、玉米秸秆、鲜牛粪或松针配施下土壤微生物量碳、氮和可溶性有机碳、氮显著大于不施肥处理（no fertilization，CK）和单施化肥处理，分别比不施肥处理和单施化肥平均高23.52%和12.66%（MBC）、42.68%和24.02%（MBN）、14.70%和9.99%（DOC）、22.32%和21.79%（DON）。化肥和有机物料配施处理中，化肥+鲜牛粪处理的微生物量碳、氮和可溶性有机碳、氮最高，比CK高26.20%（MBC）、49.54%（MBN）、19.29%（DOC）和32.81%（DON），其次是化肥+生物碳或化肥+玉米秸秆处理，而化肥+松针处理最低。土壤可溶性有机碳质量分数（308.87 mg/kg）小于微生物量碳（474.71 mg/kg），而可溶性有机氮质量分数（53.07 mg/kg）要大于微生物量氮（34.79 mg/kg）。与不施肥处理相比，化肥和有机物料配施显著降低MBC/MBN和DOC/DON，降低率分别为24.57%和7.71%。MBC和DOC、MBN和DON随着土壤有机碳（soil organic carbon，SOC）、全氮（total nitrogen，TN）的增加呈显著线性增加。MBC、MBN、DOC、DON、DOC+MBC和DON+MBN之间呈极显著正相关（P<0.01）。从相关程度看，DOC+MBC和DON+MBN较MBC、DOC、MBN、DON更能反映土壤中活性有机碳和氮库的变化，成为评价土壤肥力及质量的更有效指标。结果可为提高洱海流域农田土壤肥力，增强土壤固氮效果，减少土壤中氮素流失，保护洱海水质安全提供科学依据。

Exogenous organic materials applied to paddy field improving soil microbial biomass C, N and dissolved organic C, N

Abstract: Soil microbial biomass C, N and dissolved organic C, N are the most active organic C components, and they can serve as important and also sensitive indexes for soil in response to disturbance. The change in characteristics of soil microbial biomass C (MBC), N (MBN) and dissolved organic C (DOC), N (DON) and their interrelations were studied by setting the field plot experiment with an addition of exogenous organic materials at different organic carbon rate. The results showed that soil microbial biomass C, N and dissolved organic C, N under the combined application of mineral fertilizers and biochar, maize straw, cow dung and pine needle were significantly (P<0.05) greater than those under no fertilizer (CK) and mineral fertilizers application treatments, respectively, with an average of 23.52% and 12.66% (MBC), 42.68% and 24.02% (MBN), 14.70% and 9.99% (DOC), 22.32% and 21.79% (DON) higher than those under CK and chemical fertilizers, respectively. For the treatments of combination of mineral fertilizers and different organic materials, soil microbial biomass C, N and dissolved organic C, N in the treatment of mineral fertilizers plus cow dung were the highest, they were 26.20% (MBC), 49.54% (MBN), 19.29% (DOC) and 32.81% (DON) respectively more than those of CK treatment, and next came the treatments of mineral fertilizers plus biochar or maize straw. Soil microbial biomass C, N and dissolved organic C, N were the lowest in the treatment of mineral fertilizers with pine needle incorporated. These differences were caused by the carbon, nitrogen contents and their component differences in quality of organic materials, different microbial communities and their ability to use carbon, nitrogen in organic materials, etc. The content of soil dissolved organic C (308.87 mg/kg soil) was less than microbial biomass C content (474.71 mg/kg soil), and the content of soil dissolved organic N (53.07 mg/kg soil) was less than microbial biomass N content (34.79 mg/kg soil). The combined application of mineral fertilizers and organic material significantly (P<0.05) reduced the MBC/MBN and DOC/DON compared to no fertilization treatment, and the average rates of decrease were 24.57% and 7.71%. With the increase of soil organic carbon (SOC), total nitrogen (TN), the MBC and DOC, MBN and DON were the significant (P<0.05) linearly increase. There were the significant positive correlations (P<0.01) between MBC, MBN, DOC, DON, DOC+MBC and DON+MBN. The degree of correlation between different forms of carbon and nitrogen, DOC+MBC and DON+MBN better illustrated the changes of soil active organic carbon and nitrogen pools than DOC, MBC, DON, MBN alone, and they were the more effective indicators for evaluation of soil fertility and quality. The study provided valuable information for improving soil nitrogen supplying capacity, enhancing soil nitrogen fixation, reducing soil nitrogen loss from farmland in Erhai Lake Valley and protecting water quality and safety of Erhai Lake.