Agriculture Reference
In-Depth Information
In some regions, it's a good idea to keep orchard soils cool and moist. If
your soil is already naturally cool and moist, however, mulching can slow tree
growth in the spring, increase problems with nutrient uptake, and greatly in-
crease root diseases. In New York, researchers found that mulching greatly
increased
Phytophthora
root rot and the death rate of young apple trees.
This does not mean mulches cannot be used in your orchard; simply use
them wisely. On soils that are slow to warm in the spring and that may
already have ample moisture, delay applying mulches until early summer
and rake them out of the tree rows in early spring.
Excessively deep mulches encourage collar rot and inhibit the movement
of oxygen into the soil. Keep your mulches no more than about 4 inches deep,
and keep them several inches away from trunks and canes to reduce disease
problems.
Although often touted as adding nutrients and organic matter to the soil,
mulches do not always achieve these goals. In Swedish trials conducted over
a 4-year period, bark chip mulch did not add organic matter or biomass to
the soil and caused nitrogen deficiency in black currants, despite manure ap-
plications that provided 178 pounds of nitrogen per acre.
Although compost is a good source of plant nutrients, it also provides ex-
cellent conditions for weed seed germination and growth. Compost also does
not provide control against emerging perennial weeds. Consider compost to
be a soil amendment, rather than a weed-controlling mulch.
Organic mulches for large plantings can be very expensive to purchase,
transport, and apply. For example, applying 4 inches of bark to 3-feet-wide
strips with the tree rows on 10-foot centers requires 177 cubic yards of bark
weighing 35.9 tons per acre. Be creative and look for inexpensive, locally
available mulch materials that will be effective and meet organic standards.
Regardless of the mulch that you use, take great care to eliminate per-
ennial weeds (particularly rhizomatous weeds) before applying the mulch.
Once the mulches are in place, your weed control options become more lim-
ited as mechanical cultivation may no longer be practical. Mulches can also
make hand cultivation more difficult. Consider mulches to be a part of your
