EAGER: Self-Protection of Organic Carbon in Soil Pores under Organic Agricultural Practices

1220731（庄）。 在农业食品生产中，有机耕作实践是一种工程方法，它应用各种方法，如轮作，作物残留物还田，免耕等，以实现营养食品，生态系统健康和高土壤生产力的目标。该项目将提供有见地的信息和证据，包括评估标准，帮助农民做出优化决策，确定应采用何种农业工程实践或其组合，以最大限度地提高土壤碳固存，以及气候和土壤特性如何影响有机实践的有效性和潜力。土壤有机碳固存对土壤健康和粮食生产力有许多好处。由于农业对土壤健康的依赖，这种资源对社会至关重要。在作物生产中采用有机或保护措施可以增加土壤中有机质（OM）的投入，从而为优先考虑土壤质量和保护土壤中的有机碳（OC）创造巨大的潜力。不幸的是，控制OC应计率和能力的机制仍然不清楚。这项研究将使用一种新的综合方法来研究一种未经测试但可能非常重要的机制，该机制控制着纳米/微米土壤孔隙中碳封存的能力和稳定性。据推测，孔隙介导的土壤有机胶体，水和氮之间的反馈主导的有机农业系统中的土壤碳的命运和存储。研究目标是：（1）量化OM孔隙填充的程度（2）研究了不同温度、氮素有效性和含水量条件下有机质包封土壤的生物降解及其对土壤呼吸的影响;（3）将有机质孔隙填充、水分滞后和碳氮交互作用纳入土壤呼吸模型。将利用从两个气候和土壤条件不同的有机管理农业地点收集的土壤样本进行研究。研究将侧重于土壤微团聚体，因为它们在保护有机碳长期不被分解方面发挥着关键作用。还将检查散装土壤和淤泥/粘土组分，以进行比较。孔隙填充很可能是生态系统（特别是生物质生产系统）中土壤固碳潜力的关键机制。这项研究将是第一个通过使用最先进的小角散射（SAS）技术和基于同位素的分子签名技术的互补优势来表征土壤中孔隙介导的碳-水-氮相互作用。所获得的结果将澄清是否土壤有机质和水之间的反馈效应，在控制长期土壤碳保存在纳米/微米级孔隙中发挥关键作用的生化试剂的可及性。不同环境条件下不同孔隙中有机质分布的动态变化数据（例如，温度和水分）将揭示土壤有机质对分解的相对敏感性。OM孔隙填充和土壤呼吸之间的关系的评价将增加新的机械信息，最新的土壤呼吸模型，并澄清在何种条件下，土壤碳累积可以预期在负担得起的生产成本。 通过对美国和中国的一系列农业研究点的结果进行比较分析，将使本研究适用于特定研究点以外的地区。该研究将为农民提供采用有机或保护措施的战略指导，以同时优化粮食生产和质量，土壤碳固存以及作物对不利环境的抵抗力。该项目将通过大胆的思维和在国家实验室和中国使用新技术的实践经验，为至少三名本科生提供教育和技术培训机会。这项研究的多学科，国际方面将为本科生的研究生学习做好准备，并提高他们在制定可持续农业和减缓气候变化的科学合理战略方面的能力和承诺。该项目将促进未来中美在环境可持续性研究方面的大规模合作。

1220731 (Zhuang). In agricultural food production, organic farming practice is an engineering approach that applies various methods, such as crop rotation, crop residue return, no-tillage and others, to realize goals of nutritional food, ecosystem health, and high soil productivity. This project will provide insightful information and evidence including evaluation criteria that helps farmers make optimized decisions on what agricultural engineering practices or their combinations should be adopted to maximize soil carbon sequestration and how climate and soil properties affect the effectiveness and potential of organic practices. Soil organic carbon sequestration has many benefits to soil health and food productivity. Due the dependence of agricultre on soil health, this resource is vital important to society. Adoption of organic or conservation practices in crop production can increase the input of organic matter (OM) into soil and thereby create great potential for prioritizing soil quality and preserving organic carbon (OC) in soils. Unfortunately, the mechanisms controlling the rate and capacity of OC accrual remain unclear. This research will use a novel integrated approach to examine an untested but potentially very important mechanism that controls the capacity and stability of carbon sequestration in nano-/micro-sized soil pores. It is hypothesized that a pore-mediated feedback between soil organic colloids, water, and nitrogen dominates the fate and storage of soil carbon in organic farming systems. Research objectives are to: (1) quantify the extent of OM pore-filling (encapsulation) under different organic or conservation practices as well as water hysteresis as affected by the size distribution of OM-filled soil pores; (2) evaluate the biodegradation of encapsulated OM and its contribution to soil respiration at different temperatures, nitrogen availabilities, and water contents; and (3) incorporate OM pore-filling, water hysteresis, and carbon-nitrogen interactions into a soil respiration model. Studies will be conducted using soil samples collected from two organically-managed agricultural sites that have different climatic and soil conditions. Research will focus on soil microaggregates because of their critical role in protecting OC against decomposition over the long term. Also examined will be bulk soil and silt/clay fractions for comparison. Pore-filling very likely represents a critical mechanism governing the potential of soil carbon sequestration in ecological systems (particularly in biomass-productive systems). This study will be the first to characterize pore-mediated carbon-water-nitrogen interactions in soils by using the complementary advantages of state-of-art small-angle scattering (SAS) technique and isotope-based molecular signature technique. The obtained results will clarify whether a feedback effect between soil OM and water with respect to the accessibility of biochemical agents that play a key role in controlling long-term soil carbon preservation in nano-/micro-sized pores. Data on dynamic changes of OM distribution in differently sized pores under different environmental conditions (e.g., temperature and water) will reveal relative susceptibility of soil OM to decomposition. Evaluation of the relationships between OM pore-filling and soil respiration will add new mechanistic information to a latest soil respiration model and clarify the conditions under which soil carbon accrual can be expected within affordable production costs. Comparative analysis of results obtained from a spectrum of agricultural sites in the U.S. and China will make this research applicable beyond the borders of the particular study sites. The research will benefit farmers by providing strategic guidance on adoption of organic or conservation practices for the purpose of simultaneously optimizing food production and quality, soil carbon sequestration, and resistance of crops to adverse environment. The project will provide education and technical training opportunities to at least three undergraduate students through bold thinking and hands-on experience in using novel techniques at national laboratories and in China. The multidisciplinary, international aspects of this research will prepare undergraduate students for graduate study and enhance their capacity and commitment in developing scientifically-sound strategies for sustainable agriculture and climate change mitigation. The project will facilitate future large-scale US-China collaboration on environmental sustainability research.