Good Garden Soil

Soil is the foundation which is ultimately responsible for a healthy garden or lawn. Soil is different from "dirt" because it contains a complex mixture of mineral matter, organic matter and living organisms. It is capable of sustaining life.

It is therefore not surprising the single most important task gardeners can perform is to improve the soil quality. No amount of fertilizer, water, or other means of regulation will have as profound effect on healthy plant growth as healthy soil.

This article will answer questions such as: "What kind of soil do I need ?", "How can I get good garden soil?", "Do I need to replace the soil?".

What plants need
Besides simply anchoring the plant, soil provides certain chemical and physical properties. Plant roots must extract water and dissolved fertilizer nutrients from the soil. In addition to this, plant roots require oxygen to be present in the soil to allow them to breathe.

The optimum conditions vary by plant but generally loose, friable, water retentive soil is near ideal. It allows oxygen and water to co-exist while allowing plant roots to grow deep.

What is Soil?
The main ingredients in soil are inorganic mineral particles of clay, sand, silt, and rocks, which has been deposited on the surface over a period of many years. In the cavities formed between these particles, water and oxygen reside.

Soil is typically described based on the relative combination of the 3 particles: clay, sand and silt.

• Clay particles are very small, flat, sticky particles about 1/17,000 inch in size, e.g. they are very small, right?
• Silt is rounded particles about 10-15 times larger than clay particles.
• Sand is also rounded particle but 50-1000 times larger than clay particles (depending on the grade of sand).
• Loam is a term used about a mixture of all 3 particles in equal proportions (1/3 each).
• Since soil does not always contain the same volume of each, different "grades" of loam have been established. Examples include sandy loam which contain relatively more sand than clay and silt, whereas loamy clay contains more clay than sand and silt. There are other variations possible, too.

Each 'loam combination' has its own specific advantages and disadvantages.

The sand particles allow plenty of oxygen in the soil due to the relatively large spaces between them, but water drains too quickly below the root zone and washes out fertilizer nutrients, also.

Clay particles on the other hand tend to pack down leaving only very small spaces which fill with water but excludes air. The sticky clay particles can make it difficult for roots to grow deep. Clay is very good at holding on to fertilizer nutrients through their large combined surface area, but sometimes even too good. The chemical properties of clay soil can result in fertilizer being tied up; the clay particles bond chemically with the nutrients making them unavailable to the plants.

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