Uncovering the contribution of cover crop belowground inputs on soil carbon and nitrogen storage

增加生物多样性和保持健康的土壤对加强加拿大的粮食系统至关重要，覆盖作物可能在其中发挥重要作用。覆盖作物是种植在主要作物（如玉米、大豆、西红柿）之间的植物，在秋季到次年春季期间提供土壤保护和肥沃，而此时田地通常是光秃秃的。大多数覆盖作物的研究都集中在覆盖作物的生长季节和次年，但使用覆盖作物的种植者是长期使用的。此外，影响碳氮动态等土壤指标的变化是长期的。因此，在了解覆盖作物对农业生态系统的真正影响方面存在重大差距。******我的研究项目很好地定位于在理解覆盖作物对C和N循环的作用方面推进知识，以评估生态服务（例如减少合成肥料依赖），同时通过使用我出色的长期覆盖作物实验套件来量化作物生产力和弹性。通过这些在加拿大进行的独一无二的长期覆盖作物试验，我们观察到土壤有机质的差异，这些差异不能仅仅用地上植物的投入来解释。由于覆盖种植导致土壤有机质增加的机制是知识上的重大空白，也是NSERC提案的重点。***我的研究项目和这份DG提案的短期目标是提高对植物地上和地下投入对土壤有机碳和氮储存机制的科学认识。据推测，地下输入（根和根沉积物）贡献了大量相对稳定的有机质，这反过来又促进了C和N的保护，从而使有覆盖作物的有机C的总体长期收益比没有覆盖作物的控制。通过这个NSERC DG，我的研究计划将解决两种重要植物地下投入的相对贡献和控制因素的重大知识缺口，即根渗出物（占植物固定碳的20%）和根组织。拟议的基于农业系统的方法是创新的，因为它评估了(i)土壤和（ii）植物，（iii）环境，以及（iv）在长期覆盖作物试验中，在整个连续统中这些池之间的相互联系。通过4名HQP研究生的培训和指导，进行新颖的现场和实验室实验。提出的研究对提高加拿大农业竞争力，同时提供环境效益和土壤生态系统服务具有重要意义。最值得注意的是，我的研究项目旨在了解地下植物对C和N动态的输入，这解决了科学知识的重大空白。

Increasing biodiversity and maintaining healthy soil are critical to enhancing Canadian food systems, for which cover crops may play an important role. Cover crops are plants grown in-between main crops (eg corn, soybeans, tomatoes), providing soil protection and enrichment during the fall to following spring when fields would normally be left bare. The majority of cover crop research focuses on the cover crop growing season and the following year, but growers who use cover crops do so over the long term. Moreover, changes in soil indicators, such as those affecting C and N dynamics occur over the long-term. Thus there is a significant gap in knowledge the true impact of cover crops in agroecosystems.******My research program is well positioned to advance knowledge in the understanding the role of cover crops on C and N cycling to evaluate ecological services (e.g. reduced synthetic fertilizer dependency) while quantifying crop productivity and resiliency by using my remarkable suite of long-term cover crop experiments. Through these one-of-a-kind in Canada long-term cover crop experiments we have observed differences in soil organic matter that cannot be explained by aboveground plant inputs alone. The mechanisms driving soil organic matter increases due to cover cropping are a significant gap in knowledge and the focus of this NSERC proposal. ***The short term objectives of my research program and this DG proposal are to improve scientific understanding of the mechanisms of plant above- and below-ground inputs on soil organic C and N stores. It is hypothesized that belowground inputs (roots and rhizodeposits) are contributing significant and relatively stable quantities of organic matter, which in turn facilitates C and N protection allowing for overall long-term gains in organic C with cover crops compared to the no cover crop control. Through this NSERC DG, my research program will address a significant knowledge gap of the relative contribution of, and controlling factors of, the two plant below ground inputs of importance, namely root exudates (which constitute up to 20% of plant-fixed C) and root tissues. The proposed agricultural systems-based approach is innovative as it assesses (i) soil in addition to (ii) plants, (iii) the environment, and (iv) the interconnections among these pools throughout the continuum in a long-term cover crop experiment. Novel field and laboratory experiments will be conducted through the training and mentorship of 4 graduate HQP. The proposed research has important implications for advancing competitiveness of Canadian agriculture while providing environmental benefits and soil ecosystem services. Most notably, my research program targets understanding belowground plant inputs on C and N dynamics which addresses a significant gap in scientific knowledge.