The Mechanics of Water Erosion

Rainfall and snowmelt generate surface runoff when water falls faster than it infiltrates the soil. On sloped terrain, this runoff moves downslope, gathering velocity and picking up soil particles as it flows. The amount of soil detached and transported depends on slope angle, slope length, soil erodibility, vegetation cover, and the intensity of the precipitation event.

In Ontario, Quebec, and the Atlantic provinces — where rolling terrain is more common than on the Prairies — water erosion is the dominant form of soil loss. On heavier clay soils with low organic matter, surface crusting can dramatically reduce infiltration rates after a heavy rain, converting more of the precipitation to runoff than would occur on well-structured loam soils.

Contour Plowing and Tillage

Contour plowing orients crop rows along lines of equal elevation — across the slope — rather than up and down. This creates a series of small ridges and furrows that intercept flowing water, slowing it and allowing more time for infiltration. The approach is one of the oldest documented erosion control practices in agricultural literature.

The effectiveness of contour cultivation increases with slope angle and is most pronounced on slopes between two and ten percent. On very gentle slopes, the benefit is smaller. On very steep slopes — typically above ten or twelve percent — contour cultivation alone is often insufficient without additional structural measures such as terracing or grassed waterways.

Contour farming is most effective on uniform slopes. On irregular terrain with varying slope direction, identifying true contour lines requires careful surveying or GPS-assisted guidance. Modern precision agriculture equipment can apply contour guidance automatically using digital elevation models.

Grassed Waterways

Natural drainage pathways in a field — called draws or swales — concentrate runoff and become erosion channels if left as bare tilled soil. Establishing a permanent grass cover in these areas converts them into grassed waterways: vegetated channels that carry runoff without cutting new gullies into the field.

Grassed waterways remove land from crop production, but this area is typically the least productive part of the field due to recurring moisture and wetness issues. Seeding the channel with a durable grass mixture — smooth brome, reed canary grass, or a native species blend depending on region — creates a stable outlet for surface water while reducing sediment loss from the broader field.

Establishment Considerations

  • Seed waterways in late summer or early fall when soil is firm and grass establishment occurs before winter
  • Avoid heavy equipment traffic on newly seeded waterways during the first growing season
  • Inspect channels after major rain events; repair any rills or scour damage before they deepen
  • Maintain grass cover at a height that slows water velocity without being so tall as to trap debris

Strip Cropping

Strip cropping places alternating bands of row crops and dense-cover crops — small grains, hay, or cover crops — across the slope. The dense-cover strips intercept runoff moving through the row-crop strips above, filtering out sediment and reducing runoff velocity. This effectively breaks the slope length into shorter segments, reducing the overall erosion rate.

Strip widths depend on slope and equipment size. On steeper ground, narrower strips are more effective. On modern farms with wide machinery, adapting strip layouts to equipment width reduces headland inefficiency. Some producers align strips with field tile drainage systems or existing field boundaries.

Slope Range Recommended Strip Width Primary Method
1–2% Not typically required Residue management, cover crops
2–5% 30–40 m Contour cultivation, strip cropping
5–10% 15–25 m Strip cropping, grassed waterways
Above 10% Below 15 m or terracing Terracing, permanent cover

Cover Crops and Residue Management

A growing body of practice in Ontario and Quebec involves cover crop seeding after cash crop harvest. Cereal rye, winter wheat, radish, or legume mixes are seeded in late summer to establish fall growth before freeze-up. The living root mass improves soil structure and infiltration while the above-ground cover reduces the impact of winter rain and spring snowmelt on bare soil.

Where tillage is reduced or eliminated, standing crop residue from the previous season provides significant erosion protection during the high-risk spring period when soils are saturated and slopes are most vulnerable. Maintaining higher residue levels — by adjusting combine residue distribution settings and avoiding aggressive fall tillage — is a low-cost erosion management step available on most operations.

Buffer Strips Along Water Bodies

Riparian buffer strips — bands of permanent vegetation along streams, rivers, and drainage channels — intercept runoff and sediment before it reaches surface water. Many provincial programs in Canada provide cost-sharing for buffer establishment along watercourses on agricultural land. Buffer widths typically range from ten to thirty meters, depending on slope and regulatory requirements.

Beyond sediment capture, buffer strips provide bank stabilization, reduced stream temperature from shading, and habitat corridors for wildlife. The multi-function nature of buffers makes them a commonly recommended conservation practice in watershed management plans across Ontario, Quebec, and the Atlantic provinces.

Erosion control practices vary in effectiveness depending on soil type, slope characteristics, climate, and management context. Consult provincial conservation authorities or a certified agrologist for site-specific guidance. Many provinces offer cost-sharing programs for qualifying erosion control work on agricultural land.

Additional References