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

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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.