By Darrell Blackwelder
For the Salisbury Post
Spring is the time of year when novice gardeners complain about their soil, especially those who are trying to prepare both floral and vegetable gardens in red clay.
A major misconception about clay soils is they tend to be poor and non-productive. Observing the massive growth of an oak tree or the fact that tons of vegetables are produced per acre on these soils can easily quell this myth.
Tight clay soils are difficult to manage, but with proper modification these soils can easily produce both ornamentals and garden vegetables.
Workability of clay soils can be improved with proper soil amendments. Amending clay soils is necessary to improve drainage and oxygen. Oxygen is a very important element necessary for root growth and expansion.
The best amendments for clay soils are pine bark humus that is less than half an inch in diameter, composted leaf mold, or PermaTill. PermaTill, manufactured in Gold Hill, is slate rock which is heated and expanded, providing pore space in clay soils.
Incorporate leaf mold and other composted materials that are fully composted and not merely aged. As materials decompose, bacteria compete with plants for nutrients, especially nitrogen and sulfur, often resulting in yellowing plant growth. For heavy clays incorporate 2 inches of PermaTill by working with a shovel or tilling into the soil to a depth of 6 to 8 inches. Try to include one-half to 1 inch of compost to increase organic content if needed.
Peat moss, sand, hardwood bark, green sawdust, wood chips and pine straw are not recommended as amendments for clay soils. Adding these materials will not improve the physical properties of a clay soil. In fact, sand added to clay makes the soil more like a brick.
Amendments to clay soils must be incorporated to at least 25 percent by volume to be effective. For example, to result in approximately 8 inches of amended soil, a minimum of 2 inches of the amendment should be incorporated into the top 6 inches of soil. This also helps raise the bed which will not only improve drainage but will also make bedding plants look more attractive.
Incorporating up to 50 percent by volume will probably improve plant growth. Incorporating more than 50 percent may have a negative effect on plant growth, while incorporating less than 25 percent by volume is a waste of time and material.
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