Improve Your Garden Soil this
By Robert Cox, Colorado State University Cooperative
Extension Agent, Horticulture
All things are not created equal.
Colorado, for instance, is no Iowa when it comes to topsoil. That's one
reason gardening here is filled with challenges that result in a variety of plant
problems. But, what nature didn't provide, mankind can, at least, improve upon. This fall
is a good time to begin. Start improving your soil now by adding organic matter. You can
till or spade in leaves, cornstalks and other plant residues.
Consider the curbside garbage that goes out each week. Does it contain
recyclable materials such as pine needles and grass clippings? If so, incorporate them at
a depth of 6 to 12 inches into your soil.
What will you get in return? A soil with more nutrients that also
favors root growth. In addition, you'll be relieving already-clogged landfills.
An ideal soil for plant growth contains about five percent organic
matter, but most existing Front Range soils contain two percent or less. A three-inch
layer of material, however, is about all that a rototiller can mix into the soil at one
time. For best results, shred the organic matter and wet the soil before tilling.
Here are some additional considerations for improving your soil:
It is essential to improve soils before seeding or sodding a lawn.
Unimproved soil is a major cause of poor lawn performance or failure. Annual flower beds
and vegetable gardens also need continued amendment and will become fertile and productive
over the years.
Earthworms can help improve soils, but they prefer soils with plenty
of organic matter. You'll notice earthworms becoming more prevalent in organically rich
soils. When introduced into poor soil, they may die out.
Adding sand to a clay soil might seem a simple method of breaking up
the clay. Clay and sand, however, make a nice adobe brick! Organic matter, rather than
sand, is much more beneficial to clay soil.
What types of organic matter can you add to your soil?
Most fall leaves are good additions, although some argue that
cottonwood leaves are too alkaline to use in our alkaline soils. Cottonwood leaves are
organic, however, and when broken down, humic acids result. The advantages of cottonwood
leaves, therefore, outweigh any disadvantages.
Hay and straw should be free of weed seeds.
Weeds can be turned into the soil, if they don't have seeds on them.
Use crop residues such as cornstalks, tomato vines, and squash
plants. These can be chopped up and turned under the soil or composted. Don't,
however, use diseased plants. Dispose of them.
Pine needles make a good addition to the soil, despite their acidity.
Front Range alkaline soils resist change but several years of heavy pine needle
applications would create a somewhat more acid soil.
Grass clippings are best left on the lawn, but turning them into the
soil or using them as mulch is strongly preferred over putting them out as trash.
Kitchen wastes, such as potato and banana peels, apple cores, lettuce
leaves and grapefruit rinds benefit the soil or the compost pile. Coffee grounds are
acceptable. Egg shells can be turned into the soil, although they aren't needed to add
calcium to our already-calcium rich soils, as some suggest. Don't use meat scraps
Manures are a good addition if they are well-aged and relatively free
of weed seeds. Feedlot manures may contain excessive salt levels. Manures contribute some
plant nutrients, but their primary benefit is improving soil texture. Stable litter, often
a mix of manure and sawdust or straw, also works well.
Sawdust and wood shavings can be slow to break down in the soil, but
both are good amendments. To speed decomposition, just add some nitrogen fertilizer. Never
use walnut sawdust or shavings; walnut contains a compound that is toxic to other plants.
Wood ashes have been promoted as a good source of potassium. They
aren't recommended, however, as Colorado soils are potassium-rich. Wood ash also is quite
Sphagnum peat is recommended, because it is acidic and therefore
helps alkaline soils. It, however, is expensive. Hypnum and sedge peats are of less value
as soil amendments.
- Sewage sludge is a good soil amendment, but may contain high levels of heavy metals such
as lead and cadmium. Industrial flow into municipal sewage systems often contains these
heavy metals. Sewage sludge often is used on golf courses. At home, it's safest to use it
on lawns, flower gardens and other areas not used for growing edible produce.
Photo: Judy Sedbrook
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