连续多年施用生物炭对棕壤团聚体稳定性及土壤肥力的影响

Soil aggregates are the regulation center of soil structure and fertility. Soil organic carbon (SOC) is a key factor affecting the formation and stability of soil aggregates. Biochar is a kind of organic mater containing high ratio of carbon and much stable. It can increase the amount of SOC and improve the fertility and productivity of soil. Biochar application to cropland has been regarded as the win-win approach of increasing grain production and emission reduction in agriculture in response to the climatic change. By so far the researches about the effects of biochar application on soil aggregates are very few and the conclusions are conflicting, and the experiments were based on short-term tests, which made it difficult to get a convincing result about the effects of biochar. ..This study is based on the Braunerde soil long-term biochar application experiment started at 2009. To separate soil particulate-size organic matter, physical fractionation technique and other modern testing techniques are adopted simultaneously. The soil samples at different intervals of 3,5,7-year after the beginning as well as the original soil sample before experiment will be taken and analysed. The main research contents include as follows: soil physicochemical properties, components of soil aggregates, SOC distribution in different size of soil aggregates and its bonding form, the change characteristics of soil enzyme activities (include invertase , peroxidase and polyphenol oxidase activity) and the contents of deferent forms of Fe- and Al-oxidates (combined Fe ,combined Al, Fed, Ald, Feo and Alo).From the above researches, the regulation mechanisms and factors affecting the components and stability of soil aggregates will be elucidated, and the evolution trends of soil fertility and soil structure under years of biochar application in cropland will be clarified.

土壤团聚体是土壤结构和肥力的调节中心，有机碳是影响团聚体形成和稳定的重要因素。生物炭是一种含碳量高且更为稳定的有机碳，既可增加土壤碳储量，又可改善土壤肥力和生产力，是农业应对气候变化的增产增汇减排的双赢措施。目前关于生物炭对土壤团聚体影响的报道少而结论不一，且大都以短期试验为基础，很难取得有说服力的结论。.本研究依托生物炭棕壤田间微区定位试验（2009年开始），借助土壤颗粒有机物物理分组技术和其它现代测试技术，通过研究生物炭不同施用年限下（试验前及连续施用3年、5年、7年）土壤的理化特征及土壤团聚体组成、团聚体中不同物理组分有机碳分布及结合形态、各级团聚体中不同形态铁铝氧化物含量及土壤酶活性的变化特征，探明连续多年施用生物炭条件下土壤团聚体组成与稳定性的变化规律及其影响机制，揭示施用生物炭条下土壤结构及肥力特征的演变规律。

生物炭作为土壤改良剂对土壤改良研究的报道较多，炭基复合肥是生物炭农用的另一种方式，但目前大多为短期培养或模拟试验。不仅如此，目前更缺乏生物炭与传统土壤培肥方式的比较研究。越来越多的研究表明了相对于单施化肥或有机肥，有机无机配施对土壤肥力和生产力的重要作用。然而，在等养分下不同有机物料施用对土壤有机碳的固定作用和土壤团聚性的影响却少有研究，尤其关于生物炭的更少。.因此本研究旨在通过4年的田间微区定位试验，开展生物炭、炭基肥以及两种传统培肥方式——秸秆还田和施用猪厩肥对棕壤理化性质、团聚体稳定性及对有机碳固定的研究，以期为生物炭的培肥改土及合理农用提供理论依据。.1. 各种有机物料施入土壤后，均可增加土壤养分含量，改善土壤理化性状，使得产量不断提高。施用生物炭在提高有机碳和全氮方面效果更佳。炭基肥在调节土壤pH方面作用显著。.2. 总体上，生物炭和炭基复合肥对土壤的理化性质的改良作用与秸秆还田和施用猪厩肥相近，生物炭在提高土壤有机碳和全氮含量方面，炭基复合肥在改善土壤pH方面优势突出，对作物具有持续增产作用。.3. 水稳性微团聚体含量分布（78-80%）及其中有机碳的分配比例（81-97%）最高，大团聚体最低，它们均与水稳性平均重量直径（wMWD）显著正相关；大团聚体周转速率对团聚体水稳性和干稳性存在着负效应，与传统的培肥土壤方式—秸秆直接还田及施用厩肥相比，生物炭和炭基肥施用显著降低了MWD。.4. 生物炭或炭基肥施用有利于促使有机物质的腐解和稳定，干筛微团聚体中闭蓄态颗粒物（mPOM）或水稳性微团聚体中细颗粒物（fPOM）组分对碳固定促进作用较大，而且炭基肥处理下细粗颗粒物比值（F/C ratio=18.98）显著高于其它有机物料。.5. 干筛微团聚体中铁铝离子桥作用对团聚体水稳定性具重要影响，但对干团聚体稳定性影响不显著。粗颗粒碳和干筛大团聚体碳分配比例、（全量态氧化硅）Si(t)macro在小团聚体中的分配比例及微团聚体中氧化铝的活化度均与干筛团聚体平均重量直径（dMWD）显著正相关。. 综合上述结果，可以说明，经过4年的连续施用，与传统的土壤培肥方式相比，生物炭不利于土壤大团聚体的形成和稳定，但对土壤的其他理化性质的影响与秸秆还田和施用猪厩肥相近。