Idaho
Falls Community Garden Association
letsgrow@srv.net
THE MIRACLE OF MULCH
To mulch or
not to mulch, that is the question!
(Ham It Up. Act 1, Scene 2)
WHAT
Mulching
is the application of organic or inorganic materials (mulches) to the
soil
surface to 1) reduce weeds, and weeding!, 2) conserve soil moisture, 3)
improve
soil quality, and 4) moderate soil temperature. Ideal
mulches allow air and water to enter and exit the soil,
contribute to soil fertility, and are attractive.
WHY
Pros
(1)
Weed control/suppression
(2)
Help moisture retention of soil through
evaporation control; water conservation
(1&2,
especially, save time and work!)
3)
Add to soil nutrients; improves soil quality
and texture/structure; stimulates beneficial soil organisms; promotes root growth. Soils
in southeastern Idaho are generally
low in organics, so mulching really helps.
Organic mulches are (after partial decomposition/composting)
turned into
the soil to improve its texture, nutrients, and water retention
properties.
(4)
Soil temperature control summer and winter.
Caution: Idaho has a cooler and shorter
growing season, so mulch after soil temperature rises.
Winter mulches protect root crops,
perennials, bulbs, and spring seedlings, by equilibrating soil
temperature.
(5)
Control erosion from wind, water,
traffic. Protects the soil from rain
drop impacts and run-off; keeps soil evenly moist, prevents wind
erosion.
(6)
Aesthetics
(7)
Helps prevent compaction and crusting, allowing
seedlings to push through soil
surface.
(8)
Provides some disease barrier/control (e.g.
prevents “splashing” of disease organisms from soil to plant by air or
water).
Helps prevent fruit and vegetable rot/mold by preventing contact with
soil.
(9)
Can neutralize some toxins.
Cons
(1)
Aesthetics
(2)
Introducing and aiding weeds
(3)
Attracting and harboring pests - slugs,
insects, microorganisms, rodents
(4)
Introduction of undesirable or toxic
materials; e.g. chemicals, herbicides,
insecticides, organic chemicals (pine needles, some nut shells have
some
natural toxins; use on pathways), diseases
(5)
Some initial loss of nutrients, especially
nitrogen, with “woody” or “brown” mulches; use sulfur, fish emulsion,
blood
meal, cover cropping, for recovery. Caution!
Community Gardens are organic!
(6)
Restriction of air, water, and light
penetration - easily adjustable
Try It!
Types of
Mulch:
Summer or Growing Season Mulches:
soil temperature moderation, early frost protection for seedlings, weed
suppression.
Winter or Dormant Season
Mulches: protection
Permanent: landscaping,
paths, trees, perennial beds, weed control
Weed,
water, and till first!
Apply
as soon as possible in spring (especially around cool season crops -
peas,
lettuce, spinach, etc.) but after soil has warmed and before too many
weeds
show up. Keep both organic and inorganic mulches at least 4-6 inches
away from
plant stems. But mulching is good
anytime!
Plan
to maintain about 3” of mulch for most effectiveness.
Amount and frequency of application depends on nature of mulch,
fine vs. coarse, rate of decomposition, etc.
For
most relatively dry, loose organic mulches use/maintain 2 - 4 inches in
our
climate.
Use
less green grass clippings and other fine materials and apply more
frequently
to prevent packing and water repelling; use 4 - 6 inches for dry grass;
6 - 8 “
for straw (straw and leaves are good for temporary frost protection
over young
plants).
Use/maintain
2 - 4 inches of bark or wood chips; 1 - 3 inches of rock; best for
“permanent”
beds, trees; best to underlay bark and rock with geofabric. Geofabrics
may need
to be carefully removed after a few years.
References
Most
good gardening books and magazines will have tips on mulching.
“Mulches
for Your Garden”. 1978. (Brochure) USDA Soil Conservation Service Home and
Garden Bulletin No. 185.
“Are
Mulches a Good Idea?”. West Virginia University Extension Service.
<www.wvu.edu/~agexten/ageng/resource/mulch.html>
“Easy
Gardening...Mulching”. Texas A&M
Agriculture Program. Extension
Horticulture Information Resource Webpage.
<Http://aggie-horticulture.tamu.edu/extension/easygardening/mulching/mulching1.html>
“Mulches
for Gardens and Landscapes” New Mexico
State University College of Agriculture and Home Economics Webpage
Guide
H-121.
<www.cahe.nmsu.edu/pubs/_h/h-121.html>
“Mulches
for the Home Landscape”. University of
Nebraska-Lincoln Extension Service Webpage.
<http://ianrwww.unl.edu/pubs/horticulture/g1257.html>
“Mulching
for a Healthy Landscape”. Virginia
Cooperative Extension Webpage.
<www.ext.vt.edu/pubs/envirohort/426-724/426-724.html>
“Mulch
for Winter Protection”. Purdue
University Consumer Horticulture. www.hort.purdue.edu/ext/winmulch.html
North
Carolina State University Ag Extension
www.ces.ncsu.edu/depts/hort/hil/hil-608.html IFCG SJM 2/04
Organic
|
Aesthetic
Value |
Weed Source |
Wind
Resistance |
Resists
Compaction |
Availability |
Comments
|
|
Compost |
2 |
3 |
3 |
2 |
2 |
May “burn”
plants if not fully aged; best used as a soil amendment; expensive |
|
Lawn Clippings |
3 |
2 |
3 |
4 |
1 |
Cheap! Make
sure source not exposed to herbicides |
|
Leaves |
2 |
4 |
4 |
4 |
1 |
Cheap! Best
if chopped up; don’t allow to become compacted |
|
Straw |
3 |
2 |
4 |
2 |
1 |
Good spring
and winter protective mulch; easy to apply, remove, compost. |
|
Manure |
5 |
1 |
1 |
2 |
2 |
Poor mulch;
may “burn” plants if fresh; good compost; spread in fall, till in in
spring; cheap! |
|
Peat Moss |
1 |
4 |
4 |
2 |
1 |
Expensive;
harvesting may not be environmentally sustainable. |
|
Pine Needles |
1 |
4 |
2 |
2 |
2 |
Easy to
handle; cheap; suppresses weeds, may help acidify soil |
|
Bark Chips |
1 |
4 |
1 |
1 |
1 |
Can be
expensive; excellent for perennial beds |
|
Wood Shavings |
2 |
4 |
2 |
2 |
3 |
Good for
paths and incorporation into soil; may rob nitrogen |
|
Sawdust |
2 |
4 |
2
|
2 |
3 |
Good for
paths; apply thin layer; may rob nitrogen |
|
Waste Paper |
5 |
4 |
5 |
2 |
1 |
Includes
cardboard, newspaper; cheap, temporary, ugly; needs weighting or
covering with soil or mulch |
|
Cover Cropping |
1 |
3 |
1 |
3 |
1 |
Used to
improve soil, prevent erosion |
Inorganic
|
|
|
|
|
|
|
|
Black Plastic |
5 |
NA |
5 |
NA |
1 |
Good for
early season soil warming and weed suppression; remove later |
|
Landscape
Fabric |
4 |
NA |
2 |
NA |
2 |
Expensive;
allows air and water through, and some weed growth; not totally
permanent |
|
Crushed and
Lava Rock, Gravel |
2 |
NA |
1 |
1 |
1 |
Compatible
with many garden designs; beds and paths; often needs underlay;
requires maintenance |