Bed PreParation: insurance for success 39
facilities for processing. You can contact your local EPA office or cooperative
extension office for guidelines.
Composts offer all the benefits mentioned for organic matter in general:
wonderful soil conditioning, nutrient and microbial enrichment, and disease
suppression. As with all soil amendments, knowing what a particular compost is
made of and how it was composted is essential. What are its levels of nutrients?
(The N–P–K nutrient analysis can range anywhere from less than 0.5–0.5–0.5 to
4–4–4.) Nutrient imbalances can exist in composts; for example, low levels of
nitrogen are found in composts made from sources high in carbon, such as
woody materials or leaves. But there can be significant differences in organic
matter content with different types of compost, and one cannot truly know the
benefits or shortcomings of a given compost without test results, finding out the
same critical information as with the other amendments—organic matter
content, nutrient content and availability, pH, and source. Remember that the
organic matter content of compost affects its soil conditioning abilities. These
variables also can affect the recommended rates of application of the material.
topSoil Many people think bringing in some topsoil and dumping it on the
garden-to-be is the solution to providing “good” soil for their plants. It is not.
There are no government or trade standards that a topsoil provider must meet.
Technically speaking, topsoil is the first 2 in. of the ground. This 2 in. may or may
not be fertile soil, depending on the location. Topsoil can be low in organic
matter and nutrients. If used by itself, topsoil may do little if anything to improve
the soil. Sometimes it can take 10 yards of topsoil to equal the benefits in 1 yard of
a composted material. Topsoil also can have the further disadvantage of contain-
ing weed seeds and herbicide or pesticide residues if it was scraped off farm
fields. It is important to know your supplier and to ask for an analysis of the
topsoil you buy.
Topsoil with a high organic matter content can be useful in blends with other
organic materials where it serves as a stabilizer in otherwise light soil mixes.
Other times it can be used independently as the base soil in raised planters to be
topped off with a 6- to 8-in. layer of a good organic soil blend.
gypSum Gypsum, or calcium sulfate, is a commonly used soil conditioner for
clay soils. It helps improve the structure of only certain types of clay soils found
in the western United States. It does little or nothing to improve soils in the
Midwest or East. It can aid in the removal of salt (sodium chloride) from soils.
Sand Another questionable soil amendment depending on your soil texture.
Without delving into the soil triangle from old agronomy class days, I’ll try to
explain. If you have a soil that is already fairly high in sand, incorporating
additional sand in the soil can improve it by moving your existing soil into
another textural class—say, that of a sandy loam. But if you are working with a
soil low in sand, such as a clay or clay-loam soil, adding a little bit of sand will
make matters worse. In this texture of soil 6 to 8 in. (30 percent or more by
volume) of a very coarse sand would be needed to improve your soil. Most people
are not willing to add that much sand to their soils.
a ggregateS Other coarse soil amendment products are occasionally used
in perennial gardens to improve the aeration of heavy clay soils. Perlite, grower’s
grit (crushed limestone used in the agricultural industry as chicken feed),
ceramics, fired-clay materials such as crushed brick, and fine gravels are a few
such soil amendments that are available.
Variety seems to be the spice of an amended soil’s life. Because of the wide
scope of plants we use with very different needs, using a mixture of different
organic amendments is most beneficial. You can see from the preceding discus-
sion that each amendment has a little something special of its own to offer.
Mixing different soil amendments gives us a bit of the best of each of them.