Agriculture Reference
In-Depth Information
dispersion is typically called splash erosion. Water flowing over the surface of the soil
moves these dispersed particles and removes them from the field. More plant nutrients
are contained in the surface soil, and so as surface layers are removed so is fertility,
which decreases the soil's productive capacity.
If the water is moving as a sheet across a field and down a slope, this is called sheet
erosion. This will result in a more or less even removal of the surface layer of soil. If
water concentrates in a low area and runs off the field, then depressions will be cut in the
field. This is be called rill erosion; see Figure 9.11. Evidence of these types of erosion
are removed by cultivation, and so it may not be evident or observable that erosion has
taken place. However, when rills become too large to drive across, they are not easily
covered up and are called gullies.
To stop water erosion, first protect the soil surface from being directly hit by rain-
drops. Second, prevent water from running across the field. This can be accomplished
by mulches, plant residues, growing plants, and performing cultivation perpendicular to
the slope of the field.
Reduced-till and no-till practices are additional methods used in controlling soil
erosion. Reduced tillage, as the name suggests, involves using the minimum tillage
necessary to plant a crop, thereby limiting the exposure of soil to erosion. There is
no clear or finite definition of reduced tillage, it could mean plowing and disking at
the same time or disking and planting without plowing, however, the central concept
is to reduce the number of tillage operations necessary and to get seed growing as
quickly as possible. No-tillage or no-till involves killing all the plants growing in a
field with a herbicide and then planting directly into the soil without any further soil
preparation. This keeps the soil covered and protected from both wind and rain
erosion while the crop is growing.
What Farmers Say About No-Till
Farmers who do not use no-till have a large number of reasons why it will not
work. The field looks trashy in the spring when it is first planted. Indeed some ren-
ters have been told that they can no longer rent because they are not taking care
of the land because it looked so trashy in the spring and fall. Another complaint is
that it leaves all crop residue on the field, and this makes an ideal breeding
ground for both animal and microbial pests, for example, rabbits that eat the
young crop plants and diseases that attack crops.
Farmers who use no-till have different complaints. First, they do not see
any of the problems that the farmers who do not use no-till see as problems.
They like that there are less trips over the field; they can use tractors with less
horsepower and use less fuel, and their soil is always protected against
erosion. The complaint is that when it rains there are so many worms coming
out of the ground that it is not pleasant to walk around. This is interesting
because one often hears that agricultural chemicals kill all worms in soil.
This is apparently not the case with chemicals used in no-till farming. It is
true, however, that residues on the soil surface produce an environment
conducive to worms.
