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EAP Publication - 64
Soils & Fertilizers-Mulching
Mulching. Why mulch? What to Use?
- suffocates weeds.
- saves labour.
- reduces competition for water and nutrients.
- spares roots near soil surface, which are often damaged
MODERATES SOIL MOISTURE & TEMPERATURE FLUCTUATIONS
- keeps the soil moist by reducing evaporation and
transpiration from weeds.
- buffers diurnal and seasonal temperature changes, soil
stays warmer at night and in the fall, cooler during the
day, and in the summer.
- winter mulch decreases frost heave.
CAUTION: Mulching slows soil warming in the spring, so don't
put on too early, especially on crops that like warmth. Lettuce,
peas and potatoes do best in cool, moist soil; tomatoes,
cucurbits and snap beans prefer a warm, moist soil. Corn should
be mulched when a foot high.
IMPROVES SOIL FERTILITY AND STRUCTURE
- adds nutrients as it decomposes although it may tie up
nitrogen temporarily if high in carbon.
- reduces leaching losses and top soil loss by wind action
and rain running off the surface.
- prevents soil compaction.
- encourages earthworms, whose burrows aerate and drain
- organic matter improves soil structure.
- encourages microbial growth; CO2 evolved by
microbes may be important in stimulating plant growth.
REDUCES PEST AND DISEASE DAMAGE
- provides a permanent home for biological controls of
pests (predators) parasites, pathogens) although may also
encourage slugs and rodents. If the mulch is easily
removed, slugs may be picked up and killed so this can be
an easy way to control them, the mulch acting as a trap.
- microbial toxins released during mulch decomposition
probably help to control plant diseases. certain fungi
that catch nematodes are encouraged by soil conditions
under the mulch.
- prevents fruit from bruising or coming in contact with
the soil, thus decreasing the risk of rot.
- can markedly improve the flavour of crops, especially
small fruits, (quickly decomposing materials are best for
- a good way of planting into sod or a weedy field is to
lay the mulch down all over the field some time before
planting; this will kill the weeds and leave a soft,
What to use?
DOMESTIC AND GARDEN WASTES
- Newspapers (separated into sections, colour section taken
out because of heavy metals such as lead in the ink, the
paper held down with stones or boards)
- Grass clippings (if free of weed seeds)
- Weeds and crop residues (again if free of weed seeds,
good for winter mulch, or can be placed under more
- Old carpet strips and carpet backing
- Coffee and tea grounds, peanut shells, etc.
FOREST AND FARM WASTES
- Leaves and pine needles (can be acidic)
- Sawdust (it may be a good idea to add a nitrogen source
underneath as sawdust or other high carbon materials may
tie up the nitrogen in the soil as it decomposes)
- Bark, wood chips and shavings
- Hay and straw
- Crop residues (corn stover, tobacco stems, buckwheat
COMMERCIALLY AVAILABLE MATERIALS
- Generally we do not recommend commercial mulches as they
are usually costly and/or non-recyclable. However, these
may have to be used if appropriate materials are
unavailable from other sources.
- Peat moss (very good for improving soil texture, but will
not add much in the way of nutrients; it is also quite
- Black and clear plastic (good for warmth loving crops,
sometimes can be obtained free from the warehouse if you
ask for damaged rolls)
- Paper (if you can find a source of cheap rolls of paper;
this has been used on a large scale)
Copyright © 1981 Ecological
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