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是加强加拿大粮食系统的关键，覆盖作物可能在其中发挥重要作用。覆盖作物是在主要作物(如玉米、大豆、西红柿)之间种植的植物，在秋季到次年春季提供土壤保护和肥沃，而此时田地通常是裸露的。大多数覆盖作物的研究集中在覆盖作物的生长季和下一年，但使用覆盖作物的种植者会长期这样做。此外，土壤指标的变化，例如那些影响碳和氮动态的指标，会在长期内发生。因此，对覆盖作物在农业生态系统中的真正影响的认识存在很大差距。 我的研究计划很好地促进了对覆盖作物在C和N循环中的作用的了解，以评估生态服务(例如，减少对合成肥料的依赖)，同时通过使用我出色的一套长期覆盖作物试验来量化作物的生产力和弹性。通过在加拿大的这些独一无二的长期覆盖作物试验，我们观察到了土壤有机质的差异，这些差异不能仅用地上植物的投入来解释。由于覆盖种植而导致土壤有机质增加的机制是一个重大的知识空白，也是NSERC这项提案的重点。 我的研究计划和这项DG建议的短期目标是提高对植物地上和地下输入对土壤有机C和N储存的机制的科学理解。据推测，地下输入(根和根际沉积物)贡献了大量相对稳定的有机质，这反过来又促进了碳和氮的保护，从而使覆盖作物与无覆盖作物对照相比，有机碳总体上获得了长期收益。通过NSERC DG，我的研究计划将解决两种重要的植物地下输入，即根分泌物(占植物固定碳的高达20%)和根组织的相对贡献和控制因素的显著知识差距。拟议的以农业系统为基础的方法是创新的，因为它在长期覆盖作物试验中评估(I)土壤，(Ii)植物，(Iii)环境，以及(Iv)在整个连续体中这些池之间的相互联系。通过4名HQP毕业生的培训和指导，将进行新颖的现场和实验室实验。这项拟议的研究对提高加拿大农业的竞争力，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，我的研究项目的目标是了解地下植物对碳和氮动态的投入，这解决了科学知识中的一个重大差距。

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.