秸秆生物炭对潮土氮素转化的影响及微生物学机制

Due to its unique properties, biochar is regarded as new ways to improve soil ecosystem function and to solve soil environmental problems, which has been a hot issue in the field of soil environment throughout the world. So far, there was little systematic and in-depth research on interaction mechanisms between biochar and chemical nitrogen and microbiological mechanism associated with soil nitrogen transformation under a wheat-corn rotation system in North China plain. Corn straw biochar used as experiment material, field plot trials combined with micro-plot experiment with 15N tracing will be established in a fluvo-aquic soil of North China. The project will be intended to elucidate a) responses of soil and plant on application of straw biochar, according to effect of combined application of nitrogen and biochar on soil nitrogen transformation and its effectiveness by means of 15N tracing technique, b) responses of the number of soil nitrogen transforming bacteria and related enzymes on straw biochar by means of fluorescence quantitative PCR and soil enzymology, and c)dynamic changes of straw biochar on soil microbial community composition and dominant microflora by application of molecular ecology techniques including PLFA, PCR-DGGE and T-RFLP, so as to disclose the effect of microbial community on soil nitrogen transformation. So, the main purpose of the project will provide a scientific foundation for improving straw resources use efficiency, increasing crop production and efficiency, and protecting farm ecosystem environment.

生物炭具有独特的性质，被视为改善土壤生态系统功能和解决土壤环境问题的新途径，已成为当今世界土壤环境领域的研究亮点。迄今为止，华北小麦-玉米轮作区有关生物炭与化肥氮的互作机制、土壤氮素转化的微生物学机理，还缺乏系统、深入的研究。本项目拟以华北石灰性潮土为供试土壤、玉米秸秆生物炭为供试材料，通过田间试验和15N示踪的微区试验，采用15N示踪技术研究秸秆生物炭配施氮肥对土壤氮素转化及有效性的影响，阐明土壤和植株对秸秆生物炭施用的响应；采用定量PCR和土壤酶学等技术手段，研究秸秆生物炭对土壤氮素转化菌数量及酶活性的影响，阐明其对秸秆生物炭施用的响应；采用PLFA和PCR-DGGE等分子生态学技术，研究秸秆生物炭施用下土壤微生物群落结构组成和优势菌群的变化，揭示微生物群落对土壤氮素转化的影响，旨在为秸秆资源高效利用、作物增产增效、保护农田生态环境提供科学依据。

本项目以玉米秸秆为原料，在300℃、450℃和600℃下制备生物炭并对其进行性质表征；通过田间试验，采用土壤酶学、分子生态等方法与技术，研究秸秆生物炭对潮土氮素转化的影响及微生物学机制，主要进展如下：. （1）随着裂解温度升高，生物炭pH值、灰分、C含量、比表面积、孔体积、芳香碳及碱性基团含量均增加，而其产率、H和O含量、H/C和O/C原子比，烷基碳和表面酸性基团含量均显著降低；电导率（EC）和矿质元素总量（水溶性和交换性K、Na、Ca、Mg）均以MC450达最大值。 . （2）田间试验表明，生物炭7.5 t/hm2与氮肥150 kg N/hm2配施对提升作物产量、土壤肥力参数的效果最佳。冗余分析证实了土壤水溶性有机碳（DOC）、微生物量碳（MBC）、电导率（EC）和无机氮含量是导致土壤胞外酶活性变化的主导因素；微生物群落结构的变化与土壤水溶性有机碳（DOC）、MBC和EC含量密切相关。. （3）田间试验表明，与CK处理相比，各施肥处理均显著降低了具有硝化作用的AOA、AOB基因拷贝数，显著增加了反硝化作用关键基因nirK、nirS和nosZ的拷贝数；与N处理相比，N+MC处理显著增加了AOA、nirK、nirS和nosZ基因拷贝数。. （4）采用MiSeq高通量测序表明，AOA的优势菌门为奇古菌门， AOB和反硝化细菌（nirK、nisZ、nosZ）的优势菌门均为变形菌门，生物炭配施氮肥均显著增加了AOB（亚硝化螺菌）、nirK（根瘤菌、中慢生根瘤菌、红假单胞菌和中华根瘤菌）、nirZ（Cupriavidus）和nosZ（慢生根瘤菌）等优势菌属的相对丰度；土壤AOB的优势菌属与土壤水溶性氮（TDN）和EC显著相关，土壤反硝化细菌（nirK、nosZ）的优势菌属与TDN、EC、C/N显著相关。