Erosion - Soil Diagnostics
Almost every farm has felt the effect of some form of erosion over the years. This can have long term impacts on soil productivity. Erosion moves not only soil; it also moves and redistributes organic matter, fertilizers and pesticides.
Water erosion may not actually remove soil from a field but it can significantly rearrange soil within a field. It increases the variability of the soil and the crop growth within a field. Water erosion creates rills or small gullies in the field. It is most common early in the season on bare soils or when the crop canopy is not yet fully developed.
Eroded areas tend to display a lighter soil colour and poor soil structure. Knolls and side hills are most prone to erosion. Crops grown on eroded soils often display poor emergence, experience delayed establishment and exhibit poor growth compared with the rest of the field. Eroded knolls tend to have a lower pH, further contributing to poor crop growth.
Soil in low spots, or areas where the eroded soil is deposited, is usually darker in colour than the rest of the field. Use a soil probe to examine and compare topsoil depth in various parts of the field.
Wind erosion is a common problem on many of the coarse textured, low organic matter soils used for vegetable production. Wind erosion in the early spring may expose or remove seeds in one area of the field while deeply burying them in another. Wind blown soil can damage or kill young plants and wounds caused by blasting sand often act as a point of entry for foliar diseases. Crops are most susceptible to wind damage early in the season before the canopy is established.
moves soil in three ways:
- Suspension occurs when very fine soil particles are carried high into
the air. While highly visible, this accounts for a very small amount
of the total soil lost by wind.
- Saltation is the most damaging, accounting for more than 50% of the soil
movement usually. It occurs when fine to medium sized soil particles
are lifted a short distance into the air and drop back to the soil surface
where the particles can damage crops and dislodge more soil.
- Creep is a more gentle movement. Larger soil particles are dislodged and roll along the soil surface. This accounts for about 25% of soil movement by wind. Creep gives the soil surface the appearance of wave action or mini dune formation.
- Crop residues and cover crops keep the soil covered and slow the movement
of wind and water across the field. Cover crop roots also anchor the
soil, preventing its movement.
- Rotate vegetable crops with cereals or other crops that leave high amounts of residue. Use erosion control structures such as grassed waterways, tile drains and water and sediment control basins. Tree windbreaks and grassy wind strips slow the movement of wind and protect the adjacent crop.