设施蔬菜N吸收障碍的土壤微生物作用机制

It is well known that soil microorganism play an important role in nutrient cycling and metablism,as well as in the process of N utilization. Howerer, the research about the effect of microbes in protected vegetable soil with high-input on reduced nitrogen use efficiency need to further discuss. To better understand the effect of microorganisms on the nitrogen use efficiency in protected vegetable field, plot trial and greenhouse experiment were employed.The effect of microbial community diversity on the nitrogen use efficiency was investigated by 454 high-throughput pryosequence to obtain community diversity and the richness of prodomainant microbes; the influence of microbial functional diversity on the nitrogen use efficiency was examined through BIOLOG technique; The relationship between microbial activity and nitrogen use efficiency was measured by Microcalorimetry; and the effect of the quantity of N cycling-related microbes( such as Azotobacter, Ammonia-oxidizing bacteria, Nitrobacteria, and denitrifying bacteria) on the nitrogen use efficiency was detected by real-time PCR. The objective of the present study is to discover the relationship between nitrogen use efficiency and microbial community and activity, and deciphering the action form and role of microbs in the process of descreasing of nitrogen use efficiency in protected vegetable soil with high-put N fertilizer. The relults will provide data about the effect of microbes on N use efficiency ,at the same time, it will also provide theoretical guidance for rational application of N fertilizer.

土壤微生物对土壤养分循环代谢起着不可替代的作用，在氮素转化过程中扮演了重要角色。但在高氮肥投入的设施蔬菜土壤中微生物在氮素转化中的作用还需进一步研究。本项目拟通过设施蔬菜长期定位田间小区试验检测和温室盆栽试验验证相结合的研究模式，以青菜为研究对象，利用宏基因组技术，通过454高通量焦磷酸测序检测微生物结构多样性变化对氮肥利用率的作用，探明其中微生物的群落结构及主导菌群的丰度；通过BIOLOG 技术检测微生物功能多样性改变对氮肥利用率的影响；通过微量热技术检测微生物活性与氮肥利用率的关系；通过Real-time PCR检测固氮菌、氨氧化菌、硝化和反硝化菌数量对氮肥利用率的作用。最终通过阐明微生物在高氮肥投入的设施蔬菜土壤中氮肥利用率降低过程中发挥作用的形式，揭示微生物对氮肥利用率的作用机制，弥补设施菜地氮肥与土壤中微生物群落研究的不足，同时为设施蔬菜土壤中氮肥的合理施用提供指导。

设施蔬菜土壤中过量投入的无机养分导致土壤中养分元素累积、土壤质量退化、肥料利用率降低等一系列问题。土壤微生物在土壤养分转化过程中起着重要的作用。. 本项目利用青菜和番茄两种设施蔬菜，研究了连作条件下不同氮肥用量（1N、0.8N、0.5N和0N）和两种施肥模式中（有机肥和化肥）对土壤质量、蔬菜生长、微生物活性和群落组成的影响，阐明了土壤微生物的群落结构及微生物活性和氮素用量之间的关系；并研究了健康和发病番茄土壤微生物的群落结构特征和功能差异。结果如下：.施用氮肥会导致土壤pH下降，但对蔬菜产量无显著性差异，有机肥处理的土壤碱解氮、速效磷均呈增加趋势，高通量测序结果表明微生物的组成分布是随氮肥梯度变化的。速效 N、NO3--N和 NH4+-N作为主要环境因子驱动了微生物的变化。夏季样本中，氮肥主要驱动Firmicutes、Bacteroidetes 和Proteobacteria的变化，而冬季中Bacteroidetes、Actinobacteria和Acidobacteria 作为主要微生物类群响应来响应氮肥的使用量。除了微生物群落结构的变化，随着氮肥用量增加，土壤中固氮微生物数量和功能微生物活性在降低。. 454高通量测序结果表明发病和健康设施番茄根围微生物群落结构具有显著性差异，首先发病土壤和植株中病原菌Ralstonia solanacearum的数量显著高于健康样本，而微生物多样性以健康样本中较高。两种样本中均以Proteobacteria 为主导菌，占35.7-97.4%，其中Gammaproteobacteria 纲在健康样本中丰度更高，而Alphaproteobacteria、Actinobacteria和 Betaproteobacteria 在发病的样本中含量更高。而微生物的活性，土壤酶活性也以健康样本中高。表明土壤健康质量会引起微生物结构和活性的改变。. 本项目研究了设施菜地N肥用量和土壤微生物群落组成的关系，揭示了氮肥调控的关键微生物种类以及该过程中起主要作用的N素形态。阐明了N素调控土壤微生物变化的机制。