Berks County Cooperative Extension -

SOIL IN BERKS COUNTY

What is soil?

Soil is formed as climate and vegetation act on bedrock, a process that is gradual to say the least. The major components of soil are mineral materials (sand, silt and clay), organic matter, water and air. Most soils in Pennsylvania (need we tell you) have an abundant rock component and a root-restricting layer. Surface soil that is ideal for growing plants is composed of approximately 50% solid material (mineral material and organic matter) and 50% open or pore space. The pore space should consist of 25% air and 25% water, based upon total soil volume.

Soil structure.

Soil structure refers to the manner in which soil particles are grouped together. While most surface soil is granular, low organic content or overworking the soil may cause the structure to be indistinct. Soil structure is generally referred to as "strong" or "weak." Strong soil structure allows water and air to move freely through the surface soil; weak structure inhibits their movement. Strong structure encourages root development; weak structure does the opposite. Improving the structure of clay soils, such as those found in Berks County, by adding sand is not feasible, except for very small plots. To improve drainage and aeration in clay soils a minimum of 50% by volume of course sand must be worked into the soil - a large quantity of sand and an expensive undertaking. In some cases, adding sand may be counterproductive, as it may cause the clay to "set up" in the same manner as concrete does.

Improving the structure of soil.

Improving soil structure is a slow, ongoing process, but well worth the effort. For most home gardeners, the only practical way to enhance the structure of soil is to add organic matter. Available sources of organic matter include compost, peat moss, manure, leaf mold, sawdust, composted sludge and straw. After organic matter is added to the garden, microbes in the soil break it down. The rate at which decomposition occurs upon several factors, including availability of moisture, temperature and aeration. Warm temperatures accelerate the rate of decomposition.

Soil structure may also be improved by planting a cover crop, often referred to as "green manure." Cover crops, such as annual rye, ryegrass and buckwheat, should be sown several weeks before the first killing frost. Benefits of sowing a cover crop include:

Adding additional organic matter when the crop is tilled into the soil in the spring.
Holding soil nutrients that otherwise might be lost over the winter.
Reducing erosion and topsoil loss.

Cover crops should be tilled into the soil at least two weeks in advance of spring planting, and should not be left to go to seed.

It should be emphasized that planting a cover crop or a single application of organic matter will not produce a dramatic improvement in soil structure. Enhancing soil structure is an ongoing process that requires regular addition of amendments to the soil.

Source: The Penn State Master Gardener Manual
Document created: 15 December 1999; Revised: 3 March 2001