Agriculture Reference
In-Depth Information
helps establish a more vigorous crop to compete
with weeds effectively. Mechanical and cultural
practices, such as crop rotation and the use of
cover crops, are important components in inte-
grated weed management in potato.
and has a fibrous root system that is effective at
retaining soil nitrates. Rye has vigorous top
growth and suppresses weeds successfully. To
maximize cover crop competitiveness, growers
can stimulate weed seed germination with irri-
gation, after which the weeds can be destroyed
prior to planting the cover crop (Boydston,
2010). Rye can be controlled with a herbicide, or
plowed into the soil with primary tillage (Björk-
man and Shail, 2010).
Clover species and hairy vetch are often
used as cover crops because they are annual leg-
umes and nitrogen fixers. Both are generally
sown with a nurse crop, as they can be slow to
establish. A good stand of either is effective for
weed suppression; however, these crops are
prone to winter kill in extreme conditions. For
early-planted potatoes, clover and hairy vetch
are not the best option. Fall weed suppression
can be achieved with tillage radish, although
spring weeds will not be affected as radish win-
terkills. Tillage radish is desirable as a cover crop
due to its thick taproot, which can grow to a
depth of
14
or more inches and breaks up com-
pacted soils. A combination of cover crops may
be more effective in meeting multiple needs, with
rye being the most effective for weed suppression
(Björkman and Shail, 2010).
Cover crops are important components of
an integrated pest management system as well.
Both sudangrass and rapeseed have reduced
nematode populations when they are planted in
the fall and incorporated as a green manure
(Mojtahedi
et al
., 1993a,b; Boydston and Hang,
1995). Mustard seed and foliage contain gluco-
sinolate compounds that, when activated, pro-
duce isothiocyanates, which act as biofumigants
for the management of soilborne diseases, and
perhaps weeds (Brown and Morra, 1997).
Crop rotation
Crop rotation is an important cultural compo-
nent of an integrated weed management pro-
gram in potato. Liebman
et al
. (1996) noted the
benefits of crop rotations, including increased
yields and net profits. Well planned rotations to
include both summer and winter annual crops,
or the incorporation of cover crops prior to the
potato rotation, minimize opportunities for weeds
to germinate, emerge, and complete their life
cycle (Boydston, 2010).
Potato production in the upper mid-west
and eastern USA generally follows a rotation
where excellent weed control can be achieved.
One such crop planted prior to potato produc-
tion is field maize (
Zea mays
). Other crops grown
ahead of potato may include lucerne, soybean,
and others based on herbicide options or the
suppression of specific weeds (Westra
et al
., 1995).
Rotations in western US potato production re-
gions are similar to the other regions, as most
production occurs under irrigation. Soybean is
seldom grown in a western US rotation, but
other high-value crops, particularly onion, are
added to the rotation.
Cover crops are becoming increasingly
popular as a weed management tool in potato. In
addition to acting as a scavenger for nutrients
following the previous crop, cover crops compete
with weeds for resources, reduce growth, and
can even suppress weed seed germination. They
also fix nitrogen, improve water infiltration, sup-
press diseases and nematodes, prevent soil ero-
sion, add organic matter to the soil, and reclaim
nutrients (Clark, 2007; Griffen
et al
., 2009).
Common cover crop options used in potato pro-
duction include rye, clover, hairy vetch, and
occasionally tillage radish (Boydston, 2010).
The most widely used cover crop is rye. Rye
offers several advantages over other cover crops
for use in potato (Björkman and Shail, 2010).
Rye is a cold-tolerant grain that germinates in
cool soil, making it an ideal winter cover crop,
Crop population and variety
Potato plant population ranges according to var-
iety and region, and weed control is rarely, if
ever, a consideration of the spatial requirements
for potato. Optimal seed spacing and row spa-
cing is determined by agronomic practices in the
planting region, combined with the desired
tuber size for a given variety. Colquhoun
et al
.
(2009) reported significant variation among ten
