Tillage and cropping practices that reduce soil organic matter levels, cause poor soil structure, or result in soil compaction, contribute to increases in soil erodibility. Sand, sandy loam and loam-textured soils tend to be less erodible than silt, very fine sand and certain clay-textured soils. Generally, soils with faster infiltration rates, higher levels of organic matter and improved soil structure have a greater resistance to erosion. Texture is the principal characteristic affecting erodibility, but structure, organic matter and permeability also contribute. Soil erodibility is an estimate of the ability of soils to resist erosion, based on the physical characteristics of each soil. Runoff from agricultural land is greatest during spring months when the soils are typically saturated, snow is melting and vegetative cover is minimal. Reduced infiltration due to soil compaction, crusting or freezing increases the runoff.
Surface water runoff occurs whenever there is excess water on a slope that cannot be absorbed into the soil or is trapped on the surface. Although the erosion caused by long-lasting and less-intense storms is not usually as spectacular or noticeable as that produced during thunderstorms, the amount of soil loss can be significant, especially when compounded over time. Soil movement by rainfall (raindrop splash) is usually greatest and most noticeable during short-duration, high-intensity thunderstorms. Lighter aggregate materials such as very fine sand, silt, clay and organic matter are easily removed by the raindrop splash and runoff water greater raindrop energy or runoff amounts are required to move larger sand and gravel particles. The impact of raindrops on the soil surface can break down soil aggregates and disperse the aggregate material. The greater the intensity and duration of a rainstorm, the higher the erosion potential. The rate and magnitude of soil erosion by water is controlled by the following factors: Rainfall and runoff The widespread occurrence of water erosion combined with the severity of on-site and off-site impacts have made water erosion the focus of soil conservation efforts in Ontario. This fact sheet looks at the causes and effects of water, wind and tillage erosion on agricultural land. Soil compaction, low organic matter, loss of soil structure, poor internal drainage, salinisation and soil acidity problems are other serious soil degradation conditions that can accelerate the soil erosion process. Soil erosion can be a slow process that continues relatively unnoticed or can occur at an alarming rate, causing serious loss of topsoil. Soil erosion reduces cropland productivity and contributes to the pollution of adjacent watercourses, wetlands and lakes.
Topsoil, which is high in organic matter, fertility and soil life, is relocated elsewhere “on-site” where it builds up over time or is carried “off-site” where it fills in drainage channels. The erosive force of wind on an open field.Įrosion, whether it is by water, wind or tillage, involves three distinct actions - soil detachment, movement and deposition. The erosive force of water from concentrated surface water runoff. In agriculture, soil erosion refers to the wearing away of a field’s topsoil by the natural physical forces of water (Figure 1) and wind (Figure 2) or through forces associated with farming activities such as tillage. Soil erosion is a naturally occurring process that affects all landforms.
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