Soil Erosion in Agricultural Systems

Soil erosion in agricultural systems is a very important problem to manage. The productive layer of dirt is called the humus or topsoil. If this layer is eroded away, then the ground is very unproductive in producing crops.

Soil can be eroded away by wind and water. High winds can blow away loose soils from flat or hilly terrain. Water erosion generally occurs only on slopes, and its severity increases with the severity of the slope. In the Midwest much of the wind erosion occurs in winter when the ground is frozen, but the upper most soil layer is dry and loose. Water erosion occurs during the spring with the thawing and melting action of the snow.

There are a number of different methods of reducing soil erosion.

Contour tillage reduces water erosion. On hilly areas plowing is done across the hill rather than straight up and down. One problem with this is that some fields' shape make this method impractical. Terraces can also be constructed so to reduce water erosion.

Strong proponents of soil protection also advocate no-till agriculture. No-till is actually a misnomer. Traditional plowing cuts down and overturns up to 8" of soil. The coulter disks on traditional plows are straight disks. No-till only stirs up to 2" in creating crop rows. No-till coulter disks are waved which creates the stiring action. Traditional plowing is utilized to break up dirt clogs in heavy clay soils and to kill competing weeds. No-till reduces soil erosion by keeping crop and plant residue on the surface longer. The major problem with no-till is that weed growth can only be stopped by heavier herbicide applications than with traditional tillage methods. In this case, farmers must make the hard choice between soil conservation and heavier applications of herbicides. No-till also does not work as well in all soil types. No-till works best in sandy soils, but in the heavier clay soils, fall traditional plowing is required to break the soil up enough for adequate crop yields. No-till also does not work in compacted soils. The only way to break down soil compaction is through traditional moldboard plowing or the use of a subsoiler.

One method designed to reduce to wind erosion is the establishment of windbreaks. Windbreaks work well in reducing wind velocities over fields, but they have one serious drawback to farmers. For every quater mile of windbreak approximately one acre is taken out of crop production. Windbreaks take out not only their physical width, but they shade out crops to the side of them as well. Farmers must pay taxes, rent, and maintenance for windbreaks that produce no benefit in return.

Another method of reducing soil erosion is to leave crop residue on the field after harvesting. For example, after the corn is harvested, the stalks are left on the field all winter to reduce erosion and soil fertility decline. The major problem with this is that the the crop residue offers habitat for pests. If crop rotation isunfeasible then heavier amounts of pesticides are required to eliminate the pest problem. Again farmers must decide between soil conservation and chemical applications.