有机物料对植烟土壤氮素矿化及微生物性质的影响

采用稻草、油菜、黑麦草和菜籽饼等4种有机物料,采集高有机质含量(68.2 g·kg^–1)烟-稻轮作土壤和低有机质含量(17.2 g·kg^-1)旱地植烟土壤,在等氮(100 mg·kg^-1)投入条件下通过室内培育实验,分析了不同培育时段土壤无机氮(NO3-、NH4+)矿化动态、土壤酶活性以及微生物功能多样性的变化。结果表明:植烟土壤矿化氮动态特征与施用有机物料碳氮比(C/N)密切相关,高有机质植烟土壤中添加稻草、油菜和黑麦草显著降低土壤净矿化氮水平,而低C/N的菜籽饼添加显著促进了土壤净矿化速率,引起土壤无机氮积累。在低有机质植烟土壤添加各有机物料明显提升了土壤硝化速率,但稻草和油菜添加显著降低了培养前期土壤无机氮浓度;而菜籽饼添加显著促进了土壤的净矿化速率,在短期培养内(7 d)土壤铵态氮浓度较对照土壤增加了3.3倍~3.7倍。施入高C/N的有机物料显著提升了土壤微生物功能多样性,引起土壤酶活性增高;但不同物料添加下土壤微生物群落变异不同,诱导了对碳源利用类型不同的微生物种群变化。因此,烟-稻轮作区的高有机质植烟土壤上合理施用稻草是改善烤烟品质重要措施,而对旱地植烟土壤应更加重视高氮源有机肥料的施用,以实现不同植烟区提质增效的目标。

Effects of Application of Organic Materials on Nitrogen Mineralization and Microbial Properties in Tobacco Planting Soil

[Objective] The production of high-quality tobacco leaves is closely related to soil properties and nitrogen conversion. The use of different types of organic materials as soil amendment in tobacco cultivation to improve quality of its produce varies in effects with the type of organic material used, so it is necessary to explore how to apply rationally organic materials in the light of soil conditions.[Method] In this study, four types of organic materials, i.e. rice straw, rape straw, ryegrass and rapeseed cake, were amended separately at a rate equivalent to 100 mg·kg^-1 nitrogen into the soil samples collected from a field under tobacco-rice rotation, high in organic matter (68.2 g·kg^-1) and a tobacco field low in organic matter (17.2 g·kg^-1). Then the soil samples were incubated and analyzed periodically for mineralization dynamics of inorganic nitrogen (NO₃^-, NH₄⁺), soil enzyme activities and microbial functional diversity.[Result] Results show that mineralization dynamics of soil nitrogen in the tobacco soil were closely related to C/N of the organic material used. In the soil high in organic matter the addition of rice straw, rape straw or ryegrass significantly reduced the net nitrogen mineralization rate, and the concentration of inorganic nitrogen was 3.7~7.8 times, 1.1~1.3 times and 1.0~1.3 times lower than that in the control, respectively, while the addition of rapeseed cake low in C/N significantly increased the net mineralization rate and promoted accumulation of inorganic nitrogen in the soil. However, in the soil low in organic matter, the addition of organic material, regardless of type, significantly increased soil nitrification rate, but the addition of rice straw or rape straw significantly reduced the concentration of inorganic nitrogen in the soil during the early culture period. The addition of rapeseed cake significantly promoted the net mineralization rate in a short period of time (7 d), bringing the concentration of soil ammonium up to 3.3~3.7 times higher than that in the control soil, which indicates that soil ammonium came mainly from mineralization of the organic nitrogen in the organic material applied. Analysis of soil biological properties shows that the application of high C/N organic materials significantly promoted soil microbial functional diversity and soil enzyme activities. However, the soil microbial community varied in structure with the type of organic material applied, and with the type of carbon source utilized.[Conclusion] Therefore, rational application of rice straw in the soil high in organic matter is demonstrated to be an important measure to improve quality of flue-cured tobacco. And it is essential to pay high attention to rational application of high-nitrogen organic manure in upland tobacco fields in the light of soil properties, so as to realize the target of the production of high-quality tobacco leaves in different tobacco cultivation areas.