从土壤微生物的反馈调节剖析生物炭对南方稻田生产能力的调控机理

Soil amendment with biochar is evaluated as a means to improve soil nutrient and increase crop yield. However, the effects of biochar on soil microbial community have received much less attention than its effects on soil quality and crop growth. Focus on the relationships between soil microbial community and soil nutrient and crop growth, paddy field ecosystems with different fertilizer levels will selected as the objects of the study. The effects of biochar additions on crop growth, soil microbial community and soil nutrient will be studied by site experimental study. The changes in soil microbial biomass, flora, the abundance and diversity of the function gene and soil microbial metabolic activity will be evaluated by PLFA (phospholipid fatty acids), GeoChip 5.0 and BIOLOG (single carbon metabolism) methods. The aims of the study are to better understand the direction and magnitude of the key functional groups diversity and function change and illustrate the regulation mechanisms of biochar additions on production capacity of paddy field. The study can provide scientific foundation for assessing the ecological consequences of biochar additions on paddy soil.

生物炭在提高改善土壤养分、提高南方水稻产量方面效果明显，但作为三者纽带的土壤微生物群落如何响应外源碳添加、影响土壤养分转化过程和养分有效性，进而影响水稻产量的机理尚不清楚。本研究拟以南方稻田为对象，通过生物炭梯度增施和小区定位试验，采用基因芯片，PLFA和BIOLOG等微生物生态学技术，研究生物炭添加对水稻产量性状及产量的影响，探讨土壤微生物生物量、土壤微生物关键功能群（碳代谢、氮代谢、磷代谢等功能群）以及土壤微生物群落碳代谢能力对生物炭添加的响应特征；分析生物炭添加条件下土壤微生物关键功能群结构、碳代谢功能与土壤氮、磷等养分可获得性之间的关系；最后，揭示生物炭添加在协调土壤微生物群落结构与功能、土壤养分供给、水稻产量之间相互关系的作用。旨在阐明生物炭调控稻田生产能力的微生物学机理，为丰富南方稻田改良途径提供科学基础。

以南方酸性稻田为研究对象，采用磷脂脂肪酸、高通量测序和BIOLOG等技术系统研究了生物炭梯度增施以及和肥料减量配施对酸性稻田的生产力、土壤pH值、有机碳、养分供给能力、微生物群落的影响及其相互关系。结果表明施加生物炭对酸性稻田的生产能力具有良好的调控潜力，具体表现为：（1）与未施加生物炭的稻田相比，施加生物炭的稻田产量增幅为9.6~32.2%，且稻田的生产力及稻谷产量随生物炭施加量的增加而提高；（2）施加生物炭对土壤氮素供应影响不大，但显著改善酸性稻田土壤的pH值、提高土壤有机碳以及磷、钾供给能力；（3）施加生物炭有助于增加酸性稻田土壤微生物群落的生物量，改善土壤微生物群落结构，提高土壤细菌的遗传多样性、碳代谢功能和酶活性；（4）本研究中酸性稻田最佳生物炭添加量为60~80t/ha，在此基础上，即使减量施肥30%也不会造成土壤微生物群落和土壤肥力的退化导致稻田减产；（5）生物炭协调下，土壤pH、有机碳、碱解氮以及磷、钾可利用性的增加能显著改善土壤微生物群落的结构和功能，从而有助于提高稻田的生产力。上述结果为剖析生物炭对稻田生产能力调控效果，丰富稻田的改良途径提供了科学依据。