some situations.
is grown as a winter crop in the middle and southern
Sudan grass and sorghum-sudan hybrids are fast-
sections of the U.S. Forage radish has gained a lot of
growing summer annuals that produce a lot of growth in
interest because of its fast growth in late summer and fall,
a short time. Because of their vigorous nature, they are
which allows significant uptake of nutrients. It develops a
good at suppressing weeds. If they are interseeded with
large taproot—1–2 inches in diameter and a foot or more
a low-growing crop, such as strawberries or many veg-
deep—that can break through compacted layers, allow-
etables, you may need to delay seeding so the main crop
ing deeper rooting by the next crop (figure 10.4). Forage
will not be severely shaded. They have been reported to
radish will winterkill and decompose by spring, but it
suppress plant-parasitic nematodes and possibly other
leaves the soil in friable condition and improves rainfall
organisms, as they produce highly toxic substances dur-
infiltration and storage. It also eases root penetration and
ing decomposition in soil. Sudan grass is especially help-
development by the following crop.
ful for loosening compacted soil. It can also be used as a
Rape and other brassica crops may function as biofu-
livestock forage and so can do double duty in a cropping
migants, suppressing soil pests, especially root patho-
system with one or more grazings and still provide many
gens and plant-parasitic nematodes. Row crop farmers
benefits of a cover crop.
are increasingly interested in these properties. Don’t
expect brassicas to eliminate your pest problems, how-
Other Crops
ever. They are a good tool and an excellent rotation crop,
Buckwheat is a summer annual that is easily killed by
but pest management results are inconsistent. More
frost. It will grow better than many other cover crops on
research is needed to further clarify the variables affect-
low-fertility soils. It also grows rapidly and completes its
ing the release and toxicity of the chemical compounds
life cycle quickly, taking around six weeks from plant-
involved. Because members of this family do not develop
ing into a warm soil until the early flowering stage.
mycorrhizal fungi associations, they will not promote
Buckwheat can grow more than 2 feet tall in the month
mycorrhizae in the following crop.
following planting. It competes well with weeds because
it grows so fast and, therefore, is used to suppress weeds
cOVER cROP MANAgEMENT
following an early spring vegetable crop. It has also been
There are numerous management issues to consider
reported to suppress important root pathogens, including
when using cover crops. Once you decide what your
Thielaviopsis and Rhizoctonia species. It is possible to
major goals are for using cover crops, select one or more
grow more than one crop of buckwheat per year in many
to try out. Consider using combinations of species. You
regions. Its seeds do not disperse widely, but it can reseed
also need to decide where cover crops best fit in your
itself and become a weed. Mow or till it before seeds
system—planted following the main crop, intercropped
develop to prevent reseeding.
during part or all of the growing of the main crop, or
Brassicas used as cover crops include mustard,
grown for an entire growing season in order to build up
rapeseed, and forage radish. They are increasingly used as
the soil. The goal, while not always possible to attain,
winter or rotational cover crops in vegetable and specialty
should be to have something growing in your fields
crop production, such as potatoes and tree fruits. Rape
(even if dormant during the winter) all the time. Other
(canola) grows well under the moist and cool conditions
management issues include when and how to kill or sup-
of late fall, when other kinds of plants are going dormant
press the cover crop, and how to reduce the possibility
for winter. Rape is killed by harsh winter conditions but
of interference with your main crops either by using too
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Building SoilS for Better CropS: SuStainaBle Soil ManageMent
