Garden Soil or Concrete?

Gardening in the Piedmont area can be very frustrating to the residents of Piedmont. The soil in this area can be soft as a sponge or as hard as concrete depending upon the amount of moisture in the soil. This article will give the new gardener the knowledge to have a successful garden in the Piedmont area.

The soil is a heavy red clay soil. It takes up water very slowly, but can hold a lot of water given time to absorb it. The soil is also very slow to dry out, but is like concrete once it does dry out. This soil is also slow to warm up in the spring. Needless to say, most garden plants do not do well in this type of soil. Most plants can drown if they are in a situation that prevents adequate drainage of the excess water. The very dense nature of this soil prevents drainage as well as adequate supply of oxygen to the roots. Then in the summer as the soil dries out, it is very hard to get irrigation water down in the root zone where it is needed. This can be seen by digging in the soil after hand watering with a hose. You can usually find dry soil within ½” of the top of the soil!

Plants need a loose soil with a high organic mater content. Space is needed in the soil for the flow of oxygen and water. This loose soil allows the roots to grow and to gather the moisture and nutrients needed by the plant. The organic matter provides this loose texture as well as the micro-nutrients needed by the plant. Adding compost to the soil is an ideal way to achieve this. The problem is, it takes a lot of compost to cover a typical garden (say 30’ x 50’). Buying 20 lb. bags of compost to mix in a 4” layer would get very expensive. It also takes a lot of time and grass clippings and leaves to make that amount of compost yourself. It is highly recommend that you do learn to do this for ongoing maintenance of the garden or for smaller areas.

The way to build good garden soil is to add organic matter. This can be leaves, grass clippings, wheat straw, rotten hay, or horse manure (usually has a lot of sawdust). Use whatever you have available but be aware that some of these items can introduce weed seeds as well. There will be less trouble with weeds if your organic matter is clean of weed seeds or has been at least partially composted first. Also be aware that if the organic matter is in a fairly course form, such as un-shredded leaves, the smaller types of vegetable seeds will not germinate very well the first season.  After a year of breaking down in the soil there should not be a problem with this.  You will also notice that weed seeds do not germinate as well either!! It is also much easier to cultivate or pull weeds when the soil is loose and friable.

A recommended approach would be to begin by applying a 4”-6” layer of horse manure in the fall or early winter. This is immediately tilled or mixed into the soil as deeply as practical (8” – 10”).  By immediately tilling in the manure, there is minimal loss of the nitrogen in the manure. If the horse manure is relatively fresh, there will be sufficient nitrogen for the first growing season. If the manure is aged, then be aware that a nitrogen source may need to be added early in the growing season.  Generally accepted safe growing practices are that fresh manure should only be applied greater than 90 days prior to harvest of a crop that is not in contact with the soil (corn, tomatoes, etc). If the crop is in contact with the soil (carrots, potatoes, lettuce, etc) then at least 120 days should be allowed prior to harvest.  By spring you will be amazed at the difference in the texture of the soil. You will notice also that you will have a much larger “window of time” to work the soil at the ideal moisture level. If you try to work a clay soil when it is too wet, the result will be large clods of soil that will turn hard as concrete once they dry out. If the soil is too dry, be ready to chase the tiller into the next county as it tries to pick at the concrete.

If you are working with a smaller area such as a flowerbed, a mix of  1/3 horse manure, 1/3 soil, and 1/3 sand is a good combination. If you are planting something that needs acidic soil, peat moss or shredded oak leaves would be substituted for the horse manure. Note that adding a 6” layer of organic matter will raise the surface of the garden soil above the surrounding area. This is a benefit and will aid in creating better drainage of the soil. You will also notice that the organic matter does break down and will need to be renewed each year. However, only a 1” or 2” layer will be adequate in subsequent years.

This should give you a head start on learning how to garden in the Piedmont area. If you have questions about your specific situation, or suggestions for a future article, feel free to contact me.

Thomas Kiene,  (405) 373-2974,

ThomasRebel@pldi.net (A founding member of the Piedmont Farmers Market).