What type of soil does your garden have? Grab and handful of moist
soil-does it stick together in a muddy ball? Does it slide through your
fingers? Good soil should form a loose, crumbly ball in your hand. Check
the soil in several spots in your garden; soil type can vary from area to
area. In areas with new houses, rich topsoil may have been removed during
construction, leaving only the hardpan underneath.
Soil is composed of organic and
inorganic materials. The organic materials create spaces that allow air
and water to penetrate to the plant roots.
There are three main soil types:
1. Clay "(Heavy Soil")
Clay soil is approximately 60
percent clay, 20 percent silt and 20 percent sand. If clay soil is
squeezed when wet it will squish through your fingers. Clay is composed of
microscopic mineral particles that fit together closely and do not allow
much room for air and water. Clay soils
can contain the highest density of minerals. They drain very slowly, are
easily compacted and are the last to warm in spring. Clay soil will
typically absorb water at a rate of ½ inch per hour. There are a few
plants that prefer a clay soil but if you prefer to grow a wider variety
of plants you can amend the soil with some of the organic materials listed
below. These materials should be well incorporated into the soil, not just
placed on the surface.
Sandy soil is defined as soil
that is 60 percent sand, 20 percent silt and 20 percent clay. Sandy soil
will crumble and fall apart if squeezed when moist. Sand is composed of
large, round rock particles with spaces between particles, therefore there
is more room for air and water. It drains well and warms quickly, however
the nutrient density is low due to leaching. Plants planted in sandy soil
need more water than those in other soils. Sandy soil can be amended with
some of the organic amendments listed below. These materials should be
well incorporated into the soil, not just placed on the surface. Sandy
soil absorbs water at a rate of 2 inches per hour
Loam is the ideal soil for the
garden. If squeezed when wet, loam will form a rough, crumbly ball in your
hand. It is between 8 and 25% clay mixed with sand and organic materials.
It drains slowly enough for nutrient absorption and fast enough for air to
penetrate for root growth. If your soil is loam consider yourself lucky
and care for it well with infrequent organic amendments. Loamy soil
absorbs water at a rate of 2 inches per hour.
There are two types of soil additives:
organic and inorganic.
1. Organic Additives
Because all organic matter is
constantly decaying, all types of soils can benefit from an occasional
application of organic matter. These include ground bark, peat moss,
sawdust, wood shavings, manure, compost and plant remains. Add 25 to 50
percent of soil volume and mix in
thoroughly. Humus is the final result of organic matter decay.
The result of composting is
humus. It improves drainage and aeration, as well as improving water
retention in sandy soil. Homemade humus is the best amendment you can give
your soil. After any application of homemade compost, be sure to give your
soil a little extra nitrogen to compensate for nitrogen loss during the
decomposition process. Most commercially sold organic amendments are
nitrogen fortified so microorganisms don't steal nitrogen from the plants
during the decomposing process. To do this, add 1 pound of ammonium
sulfate for every 1 inch layer of organic matter over 100 square feet.
Excessive use of organic materials can result in overly acid soil.
2. Inorganic Additives
Perlite, pumice, vermiculite
are common inorganic additives. They are used to increase drainage of clay
soils and increase water retention of sandy soils by creating pockets in
Chemical fertilizers are a
temporary solution to a long-term problem. Before applying heavy doses of
chemical fertilizer, try to amend your soil for the long term with organic
additives, compost and humus. Lime and gypsum are two commonly used
chemical additives. Lime raises the pH of overly acid soils. Both lime and
gypsum can improve drainage of clay soils. Apply gypsum in high alkaline,
high sodium soils; add lime in acid soils. Lime adds calcium, gypsum adds
calcium and sulfur.
pH range for best plant growth is between 5.5 and 7.5. Acid soil has a pH
6.9 or lower and alkaline soil has a pH 7.1 or higher. Neutral soils are
pH 7. The pH affects the solubility, and
therefore the availability of minerals in the soil. There are home tests
to determine soil pH but a professional soil test will not only tell you
the pH rating of your soil but will also tell you the exact amendments you
need to apply. Acid soils are usually deficient in phosphorous and
alkaline soils usually lack manganese, boron and phosphorus.