EVALUATION OF THE EFFECTS OF SOIL COMPACTION ON HYDROLOGY AND SOIL EROSION

土壤压实是现代农业中的一个主要问题，人们怀疑这一过程在很大程度上是与精准农业减产相关的生产力损失有关的。通常被定义为土壤颗粒重新排列的过程，土壤压实减少了它们之间的空隙并使它们更紧密地接触。全世界压实土壤的空间面积估计为6800万公顷，仅在欧洲，土壤压实就导致3300万公顷耕地退化。加拿大和美国也出现了类似的问题。尽管压实被视为传统农业中最严重的环境问题之一，但它也是最难识别的退化类型，因为症状并不总是从表面上看出来。土壤紧实度降低了入渗率，从而导致径流增加，侵蚀加剧，养分和杀虫剂流失到地表水中。压实区的空间分布极有可能改变水文和沉积物的连通性。此外，入渗减少间接影响地表和地下排水系统的效率，并增加洪水风险。因此，为了防止破坏和恢复受灾地区，必须开发更先进的建模工具，创建测绘工具，并优化耕作做法和农业机械。拟议研究计划的长期目标是增加我们对土壤紧实度的空间分布如何影响流域尺度的水文和土壤侵蚀的了解。结果将为改进与应用有益管理做法(BMP)有关的监管政府政策提供坚实的科学支持，并建立更准确地识别污染源的方法。这项研究计划的短期目标是：(I)加深我们对土壤压实对土壤土壤层尺度上的径流产生和侵蚀的影响的理解；(Ii)了解紧实区对流域尺度上水文和沉积物连通性的空间分布影响；以及(Iii)基于目标(I)和(Ii)的结果，开发一个能够考虑土壤紧实度对流域水文和沉积物连通性影响的分布式水蚀模型。这些研究计划将极大地提高我们对土壤压实如何影响流域水文变化的理解。解决这一问题对正在进行的农业和地球科学研究至关重要，因为到目前为止，很少有研究试图说明土壤压实如何影响风暴期间泥沙和养分的扩散和集中迁移。这一专题的研究对于在泥沙和养分流失严重并对地表水质量构成严重风险的地区制定管理战略至关重要。然而，土壤压实过程改变连通性和相关的营养物质和沉积物运输的方式仍然不清楚，可能因每个流域而异。对加拿大而言，这些成果将为改进与生物多样性管理计划(BMPs)应用相关的政府监管政策提供坚实的科学支持，并为更精确地确定农业流域污染源建立新的方法。

Soil compaction presents a major issue in modern day farming, and it is suspected that this process is to a large extent responsible for losses in productivity associated with yield reduction in precision agriculture. Commonly defined as the process by which soil grains are rearranged, soil compaction decreases the void between them and brings them into closer contact. The spatial extent of compacted soil is estimated at 68 million hectares worldwide, and in Europe alone soil compaction is responsible for the degradation of 33 million hectares of arable land. Similar problems have been reported in Canada and the USA. Although compaction is viewed as one of the severest environmental problems in conventional agriculture, it is also the most difficult type of degradation to identify because the symptoms are not always apparent at the surface. Soil compaction reduces infiltration rates, which leads to increased runoff, enhanced erosion and loss of nutrients and pesticides to surface water. It is very well possible that the spatial distribution of compacted areas alters hydrological and sediment connectivity. In addition, reduced infiltration indirectly affects the efficiency of surface and subsurface drainage systems and increases flood risk. Therefore, in order to prevent damage and rehabilitate affected areas, it is essential to develop more advanced modeling tools, create mapping tools, and optimize tillage practices and agricultural machinery. The long-term objective of the proposed research program is to increase our understanding of how the spatial distribution of soil compaction affects the hydrology and soil erosion at the watershed scale. Outcomes will provide a solid scientific support for improving regulatory government policies related to the application of beneficial management practices (BMPs), and establish methods of identifying contamination sources with better precision. Short-term objectives of this research program are: (i) to increase our comprehension of the effects of soil compaction on runoff production and erosion at the scale of the soil pedon; (ii) to understand the spatially distributed impact of compacted areas on hydrological and sedimentological connectivity at the watershed scale; and (iii) based on the findings of objectives (i) and (ii), to develop a distributed water erosion model able to account for the effects of soil compaction on watershed hydrological and sedimentological connectivity. These research program will significantly improve our understanding on how soil compaction contributes to changes in watershed hydrology. Addressing this issue is of paramount importance to ongoing agricultural and earth science research because very few studies to date have attempted to illustrate how soil compaction can influence diffuse and concentrated sediment and nutrient transport during storm events. Research of this topic is essential for developing management strategies in areas where sediment and nutrient losses are significant and present serious risks for the quality of surface waters. However, the manner in which connectivity and associated nutrient and sediment transport are modified by the process of soil compaction remains unclear and may be specific to each watershed. For Canada, Outcomes will provide a solid scientific support for improving regulatory government policies related to the application of (BMPs), and establish new methods for the identification of contamination sources of agricultural watersheds with better precision.