crop. Cover crops are commonly interseeded at plant-
Intercropping has many benefits. Compared with bare
ing in winter grain cropping systems or frost-seeded
soil, a ground cover provides erosion control, better
in early spring. Seeding cover crops during the growth
conditions for using equipment during harvesting,
of economic crops (figure 10.5c) is especially helpful
higher water-infiltration capacity, and an increase in soil
for the establishment of cover crops in areas with a
organic matter. In addition, if the cover crop is a legume,
short growing season. Delaying the cover crop seeding
a significant buildup of nitrogen may be available to
until the main crop is off to a good start means that the
crops in future years. Another benefit is the attraction of
commercial crop will be able to grow well despite the
beneficial insects, such as predatory mites, to flowering
competition. Good establishment of cover crops requires
plants. Less insect damage has been noted under poly-
moisture and, for small-seeded crops, some covering of
culture than under monoculture.
the seed by soil or crop residues. Winter rye is able to
Growing other plants near the main crop also poses
establish well without seed covering, as long as sufficient
potential dangers. The intercrop may harbor insect
moisture is present (figure 10.7). Farmers using this
pests, such as the tarnished plant bug. Most of the
system usually broadcast seed during or just after the
management decisions for using intercrops are con-
last cultivation of a row crop. Aerial seeding, “highboy”
nected with minimizing competition with the main crop.
tractors, or detasseling machines are used to broadcast
Intercrops, if they grow too tall, can compete with the
green manure seed after a main crop is already fairly
main crop for light, or may physically interfere with the
tall. When growing is on a smaller scale, seed is broad-
main crop’s growth or harvest. Intercrops may compete
cast with the use of a hand-crank spin seeder.
for water and nutrients. Using intercrops is not recom-
Intercrops and living mulches. Growing a
mended if rainfall is barely adequate for the main crop
cover crop between the rows of a main crop has been
and supplemental irrigation isn’t available. One way to
practiced for a long time. It has been called a living
decrease competition is to delay seeding the intercrop
mulch, an intercrop, polyculture (if more than one
until the main crop is well established. This is some-
crop will be harvested), and an orchard-floor cover.
times done in commercial fruit orchards. Soil-improving
intercrops established by delayed planting into annual
main crops are usually referred to as cover crops.
Herbicides, mowing, and partial rototilling are used to
suppress the cover crop and give an advantage to the
main crop. Another way to lessen competition from the
cover is to plant the main crop in a relatively wide cover-
free strip (figure 10.8). This provides more distance
between the main crop and the intercrop rows.
Cover Crop Termination
No matter when you establish cover crops, they are
usually killed before or during soil preparation for the
next economic crop. This is usually done by mowing
(most annuals are killed that way) once they’ve flow-
Figure 10.7. Winter rye interseeded with maturing soybeans.
ered, plowing into the soil, using herbicides, rolling and
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Building SoilS for Better CropS: SuStainaBle Soil ManageMent
