Want a great garden? Proper soil preparation is the first, and perhaps most important, step in the process. Unfortunately, too many people ignore this step and pay a heavy price in poor plant growth and survival over the following years.

With very few exceptions, vegetables, flowers, vines, roses, grass, and other plants all need good drainage, a pH in the 6.0 to 6.5 range and adequate nutrient levels. Clay soils with their very small particles tend to drain poorly while sandy soils which have larger particles drain too well and do not hold nutrients.

An ideal soil is composed of about 25% air space, 25% water, 5% organic matter and 45% minerals. Over time, most soils become compacted and lose the air and water spaces. The organic matter is constantly being decomposed by soil organisms. The great thing is that the problem with both types of soil can be alleviated by adding organic matter. Coarse materials such as leaves, shredded wood chips and manures which have been composted tend to work best. In clay, these materials open up air spaces and allow for better drainage. In sand, organic matter clogs some of the larger pores and absorbs both water and nutrients so they are available to plant roots.

How much organic matter should be added? Some people say that there is no such thing as too much. Practically speaking, around 25 to 33% by volume should be added when preparing the soil. This means that 2 or 3 inches of organic matter should be worked into the top 8 inches of soil. Use 4 or 5 inches if the soil is worked to a depth of one foot.

Every avid gardener has a recipe for soil preparation. Some like to add green sand and sphagnum peat moss. Others recommend using only manure from Rhode Island Red chickens collected by the light of the first full moon.

In the end, adding plenty of organic matter and turning the soil with a shovel or rototiller to re-establish the proper balance are of paramount importance. This will go a long way in establishing a "healthy" soil. Adding air spaces encourages aerobic organisms needed to break the organic matter into its component parts which releases nutrients to the plants. Plant roots need oxygen to fuel the process of nutrient and water uptake.

Notice that trees were not included in the list of plants that benefit from amending soils. Generally, when planting trees, only the original soil taken from the hole should be used as backfill. Technically, trees would also benefit from soil amendments but only if the entire root zone of the mature tree could be amended. For a maple or other large tree, this would require changing the soil in a huge area. It just is not practical.

Adding a little peat moss or compost to the planting hole of a tree often creates more problems. The roots of the trees tend to stay in this small area of wonderful soil and never move out into the adjacent native soils. After several years, the root system may still be quite limited and unable to support the tree during times of stress. In clay soils, a "bathtub" effect may be formed where water stagnates in the bottom of the hole and kills the root system.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


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