At this point in the season, winter seems to be too long. But, then there appears that mid-winter hope that spring really will come–the gardener's seed catalogs. Filled with colors and descriptions of luscious vegetables, these catalogs can really get you in the mood for gardening.
For many of us, the seed catalogs do set the cogs rolling towards planning the spring garden. One of the first factors that often come to mind is the soil–and with that, the realization that urbanization has given us the gift of clay soils.
Most of Illinois was covered by several inches or feet of black top soil, more in open and rural areas and less in forested lands. However, when new homes are built, most of the top soil is hauled away, and/or the surrounding soil structure is changed, making it difficult to grow plants.
First of all, clay isn't all bad. Actually, clay is a mineral-rich type of soil. The problem is that many of the minerals in clay soils are in a chemical form that your petunias, peppers and peas cannot use. We say these minerals are "unavailable."
To add to the problem, the physical structure of clay makes it heavy and compact, with small pore spaces leading to little or no drainage. Such conditions add up to poor aeration, making it difficult, if not impossible, for the root hairs of seedling vegetables to spread out and support the plant. Subsequently, the seedling does not have adequate roots for the water absorption and the mineral intake that is necessary for normal plant development.
Fortunately, for those who wish to raise trees, shrubs, flowers and vegetables in spite of their soil's condition, materials can be added to amend the soil.
Most Illinois soils are not deficient in nutrients, even a clay soil. Adding nutrients to a clay soil really won't encourage plants to grow bigger or faster. What plants need is the ability for the roots to grow and expand–and as they do, the plant grows. Organic matter is what is needed. Organic matter is any loose, crumbly soil-like material that results from the decomposition of plant and animal residue.
Compost is one type of organic matter usually made by mixing layers of leaves, stems, soil and grass clippings until the entire pile has heated up and decomposed into a usable soil-amender.
Manure is another good source of organic matter, as is rotted leaves. Most of us are familiar with the various animal manures, preferably aged to allow the partial breakdown of nutrients, remove some of the aroma and allow for easier incorporation into the soil.
Another type of manure is "green manure," which refers to vegetation such as winter wheat or other crops that are planted in the fall and turned under in the spring. They can help flower and vegetable gardens, but aren't practical for lawns and turf.
All of these organic matters serve the same purpose: they improve soil tilth. A soil that is dark, moist and high in organic matter is easier to cultivate and slow to compact. By deeply spading in quantities of manure or compost, experienced gardeners build a soil that is rich in available minerals, breaks up the compaction of clay soils and recycles the garden's refuse.
What won't work in Illinois is gypsum, though it is often sold as a soil conditioner. Gypsum would work on iron or sodium based soils by replacing those elements with calcium, which can force soil particles apart. Unfortunately, Illinois soils are calcium based, and replacing calcium with calcium has not shown any benefit.
Source: David Robson, University of Illinois Extension horticulture educator, Springfield Center, (217)782-6515
