Tillage and cropping effects on the fate of crop derived-c and n and turnover of soil organic matter

陆地碳的三分之二以土壤有机质（SOM）形式储存在农业、森林和草原土壤中，因此它是全球碳的主要储存库，SOM动态的变化可以影响全球大气二氧化碳（CO2）水平。有机质对植物和动物的生命也至关重要，因为它改变了土壤的物理，化学和生物特性，包括养分和水分保持，抗侵蚀性和土壤肥力。尽管这一核心作用，土壤有机质的性质和动态的影响，土地利用变化或全球变暖是知之甚少-它被认为是地球上最复杂的混合物。农业生态系统占土地面积的11%，管理措施直接影响SOM的形成和周转。最近，这些土壤已成为一个主要的研究热点，因为SOM的潜力，以减轻气候变化：土壤已经失去了30-50%的原始SOM，但可以管理成为一个主要的全球水库大气CO2，其中植物C被隔离为SOM是几百到几千年的年龄。我的研究项目是研究农业实践和土壤特性如何影响有机质成分，这对于制定隔离C。拟议的研究将进行土壤和作物样本收集在一个长期的现场位于德里，ON。这些田间地块建立于1988年的一个网站上，自1933年以来，烟草秋季黑麦轮换。土壤是壤土砂，允许研究SOM成分的粘土的混杂影响。它包括三种种植制度（玉米连作、大豆-小麦轮作和烟草-黑麦轮作），采用两种耕作制度，即CT使用犁板-圆盘耕作和NT。我们的目标是确定的数量和组成的SOM的变化，从以前的烟草黑麦CT旋转的种植顺序和耕作的转变。 由于SOM池的可测量的变化发生缓慢，这个网站已经到位了20年的事实是非常宝贵的。它被认为是世界上唯一一个含有14 C和15 N标记的作物残留物并允许测量δ 13 C的长期站点，因为从C3（烟草-黑麦）转换为C4（玉米）物种。

Two-thirds of the terrestrial C is stored as soil organic matter (SOM) in agricultural, forest and grassland soils, therefore it is a primary storehouse of global C and changes in the dynamics of SOM can influence global levels of atmospheric carbon dioxide (CO2). SOM is also critical for plant and animal life because of it modifies soil physical, chemical and biological properties, including nutrient and water retention, erosion resistance, and soil fertility. Despite this central role, the nature and dynamics of SOM as affected by land-use change or global warming are poorly understood - it is considered to be the most complex mixture on earth. Agricultural ecosystems account for 11% of the land area and management practices directly affect SOM formation and turnover. Recently these soils have become a major research focus because of the potential for SOM to mitigate climate change: the soils have lost 30-50% of their original SOM but could be managed to be a major global reservoir for atmospheric CO2 where plant C is sequestered as SOM that is hundreds to thousands of years old. My research program studies how farming practices and soil properties affect SOM constituents and is critical for devising strategies for sequestering C. The proposed research will be conducted on soil and crop samples collected at a long-term field site located at Delhi, ON. These field plots were established in 1988 on a site in tobacco-fall rye rotation since 1933. The soils are loamy sand, allowing study of SOM constituents free of the confounding affects of clay. It includes three cropping systems (continuous corn, a soybean-wheat rotation and a tobacco-rye rotation), under two tillage regimes, CT using mouldboard plough-disc tillage and NT. The goal is to identify changes in the quantity and composition of SOM resulting from a shift in cropping sequence and tillage from the previous tobacco-rye CT rotation. Since measurable changes in SOM pools occur slowly, the fact that this site has been in place for ~20 yr is invaluable. It believed to be the only long-term site in the world containing 14C- and 15N-labelled crop residues and allowing measurements of delta 13C because of the switch from C3 (tobacco-rye) to C4 (corn) species.