Agriculture Reference
In-Depth Information
year. Permanent (or at least long-term) alley crops eliminate or reduce the
need to cultivate the alleys, protecting the shallow tree roots.
Permanent cover crops should be very durable and resistant to wear from
machinery and foot traffic. Particularly in organic orchards, where there are
few approved herbicides, the cover crops must be noninvasive or they can
move into crop rows and become weed problems themselves.
Permanent alley crops can be sod-forming or bunch-forming grasses, al-
falfa, clovers, or mixes of these and other crops. You need to match the alley
crops to your climate and irrigation practices.
Low-Growing, Bunch-Forming Grasses
In northern Idaho trials, I had success with a variety of sod-forming and
bunch-forming grasses as orchard alley crops. A combination of sheep fes-
cue, hard fescue, and white clover worked well as a low-maintenance alley
crop, although this combination was slow to establish and benefited from
sprinkler irrigation during the planting season. The advantage of this type
of blend is that the fescues are naturally low-growing and become dormant
during the dry summers, minimizing competition with the trees for mois-
ture and reducing the need to mow the alleys. Various other bunch-forming
grasses are available that are adapted to different climates.
A problem with low-growing, bunch-forming grasses is that they are not
particularly good at competing with weeds. Especially troublesome are deep-
rooted perennial weeds, such as Canada thistle, and spreading rhizomatous
weeds such as quack grass. Make sure you have perennial weeds well un-
der control before planting slow-to-establish or otherwise poorly competitive
cover crops. Another drawback to the low-growing covers is that they pro-
duce very small amounts of clippings that can be blown into the tree rows to
serve as mulch.
In areas with cold winters and particular types of soil, bunch-forming al-
ley crops can suffer severe damage due to frost heaving. This damage makes
weed invasion likely and occurred during my Idaho trials. Despite that, the
fescues persisted and continued to provide a reasonably good working sur-
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