Soil: The "Below-Ground" Plant Environment!
Soil not only provides a physical medium in which your plants grow, it is also a reservoir of nutrients, air, and water – three requirements for plant growth.
Why you should care!
Awareness of the properties of your garden soil will allow you to adapt your cultural practices so your soil environment will be most conducive to healthy plant growth.
What kind of soil do you have?
Mineral soils, the most common soil type, are classified by particle size – clay, silt, and sand. The soil texture is the relative percentages of these different sized particles in your soil. In most soils, one of these particle sizes predominates and this is used to classify your soil. Since silt is usually present in small quantities, most soil is classified as either sandy (largest particle size) or clay (smallest particle size).
Clay soils are made up of small plate-like particles and thus have the smallest pore spaces (spaces between particles). This causes very slow drainage and is why clay soils waterlog so quickly. Clay soils are easily compacted when wet which further reduces pore space and makes the drainage problems even worse. This is a common problem around new construction where heavy equipment packs down the soil. On the positive side, clay soils have the capacity to hold lots of nutrients!
Sandy soils are made up of large (relatively), irregularly shaped particles. These create large pore spaces and are thus fast draining and dry out very quickly. Sandy soils do not compact but they also do not hold fertilizer nutrients well, as the nutrients tend to quickly wash out of the soil due to the fast drainage.
Loam soils are the best of all worlds because they are made up of a combination of sand, silt, and clay, possessing characteristics of each relative to the amount of each in the soil. Loam soils hold water – yet not too much; they hold nutrients; and they don’t compact like heavy clay soils.
OK – It's not perfect! Now what?
The number one solution for poor soil, whether it is clay or sandy, is to add organic matter. Even in small quantities, the addition of organic material greatly improves the quality of your soil for several reasons:
It provides a source of nutrients as it decomposes, acting like a slow release fertilizer.
It improves the structure of clay soils. As organic matter decomposes, it releases humic acid which acts as a glue to bind tiny clay particles together into larger aggregates, thus giving it properties more like sand and allowing it to drain better.
It improves the water and nutrient holding capacity of sandy soils by acting like a sponge.
It improves aeration and stimulates healthy root formation.
It adds beneficial microbes to the soil which speed up decomposition and thus the release of nutrients to the soil. This helps keep the soil in a healthy, balanced condition.
Sources of organic matter
There are many different forms of organic matter that can be added to your soil to help improve its texture and structure. Different types, such as Leafgro® or ComPRO®, can be found pre-packaged in large bags at your local garden center. Good organic material can also be brought in by the truckload or you can create it yourself in the form of compost or shredded leaves. In many cities, composted leaves are available free of charge or for a nominal fee – you might just have to call and arrange to pick it up. Other forms of organic matter to enrich your soil are: leaf mold, peat moss, composted manure, composted hay or grass clippings, green manure (a cover crop such as alfalfa that is tilled under in spring), and shredded bark mulch.
The Bottom Line!
Adding organic matter to your soil, regardless of what type of soil you have, can only improve it. Deep well-drained soils with good soil texture hold a lot of nutrients and retain the optimum amount of water. The addition of good organic material makes poor soils better and good soils great!