不同盐碱程度对还田秸秆腐解过程及土壤团聚结构的影响

Returning crop straws to soil not only can reduce the salinity， but also help to build up a fertile soil layer， thereby improving the production capacity in saline-alkali soils. To improve soil structure and fertility， the effect of different salinity degree on straw decomposing process and the soil aggregate structure is great significance in saline-alkali soils. Thus， laboratory culture experiment will be conducted to study the changes of the material composition of straws， soil microbial system， soil aggregate， and soil carbon under different salinity degree. Four treatments will be used: unsalted soil as control and three levels of salinity set up (2‰， 4‰， and 6‰). The changes of material composition will be measured by using nuclear magnetic resonance (NMR) technology in the straws decomposing progress， thereby revealing the co-evolution of material composition and soil microorganism. In addition， soil micro-aggregate structure and distribution characteristics of carbon will be measured by using the electron microscopic observation technology and synchrotron radiation spectrum technology， and then the effects of straws turnover on the regulatory function of the structure and the nutrient supply capacity will be investigated. Also the interaction effects among the different parameters of straws and soils will be studied. The results will clarify the evolution process soil fertility and the main controlling factors under different degree of salinity， and provide theoretical basis for revealing the mechanism of fertilizing in saline-alkali soils.

在盐碱地区进行秸秆还田有利于构建“淡化”与“肥沃”效果并存的耕作层。研究不同盐碱程度对秸秆腐解过程及土壤团聚结构的影响对于改良盐碱农田土壤结构、确立盐碱农田培肥目标意义重大。本项目拟采用室内培养试验，以非盐碱土为对照，模拟研究轻、中、重三种不同盐碱程度土壤（全盐量分别为2‰、4‰、6‰）对玉米秸秆还田培肥过程中物质组分、土壤微生物系统、团聚体及其碳素分配等指标的影响。利用核磁共振技术检测秸秆腐解过程中物质组分变化，研究其与土壤微生物的协同演变规律；利用电镜观测、同步辐射光谱等技术检测土壤微观团聚结构及其碳素分配的变化规律，分析秸秆培肥对土壤结构与养分供应能力的调控作用；并系统分析各指标之间的耦合作用。研究结果可明确秸秆还田培肥不同盐碱程度土壤的肥力演变过程及主控因素，为揭示其培肥机理提供理论依据。

研究不同盐碱程度对秸秆腐解过程及土壤团聚结构的影响对于改良并培肥盐碱农田，改善盐碱土壤结构意义重大。本项目采用室内培养试验，在研究轻、中、重三种盐碱程度对玉米秸秆腐解过程中物质组分、微生物系统、土壤团聚体特征及其碳素分配规律的影响方面取得进展。研究结果表明：（1）盐碱环境会显著延缓秸秆的腐解和矿化速率，降低秸秆还田后土壤呼吸速率与CO2的排放；（2）盐碱环境显著降低秸秆还田后土壤微生物数目，使菌种丰富度和微生物多样性下降，并减少土壤微生物量碳氮的含量，降低土壤酶的活性，推迟土壤酶活性高峰期出现的时间；（3）盐碱环境会延缓秸秆还田后土壤团聚结构的改善，降低土壤孔隙度，尤其不利于土壤大团聚体的形成，并且降低土壤的团聚度和稳定性；（4）盐碱环境造成秸秆还田后土壤各级团聚体有机碳含量的降低，不利于土壤大团聚体碳的固定，但会提高微团聚体有机碳贡献率；（5）盐碱程度的提升，会加重其负面效应。项目结果为揭示秸秆还田培肥不同盐碱程度土壤的机理，确立盐碱农田改良培肥目标提供了科学依据。