Healthy soil is the foundation of a productive vegetable garden
Good-quality garden soil:
- Contains nutrients essential for plant growth.
- Holds onto soil water but drains well.
- Allows for air movement.
These qualities are important because soil is the medium plants use to supply themselves with nutrients and water. Additionally, soil anchors plants to the ground by providing a secure place for plant roots to grow.
Soil composition
A typical soil is made up of about 45 percent minerals, 25 percent water, 25 percent air, and 5 percent organic matter.
- The mineral portion contains sand, silt and clay from weathered rock. The mix of these soil separates determines the soil's texture. Soil with a high proportion of sand may drain so well that it can't hold on to any water or nutrients. The other extreme is a clayey soil. Clay particles are small and tightly packed. Water can not flow easily through clay soils.
- Soil water contains dissolved nutrients from minerals and decayed organic matter, plus a "soup" of microorganisms.
- Soil air is a place for plant roots, microorganisms and other soil dwelling creatures to take up oxygen and release carbon dioxide.
- The organic matter portion of soil is small but very important. Organic matter is dead and decaying plant and animal matter. Organic matter provides nutrients, improves a soil's water-holding capacity, and supports a diverse population of beneficial soil organisms. Organic mulches (like straw) and cover crops like rye, oats, buckwheat, and clover contribute to soil organic matter as they decompose. Animal manures and composts also are excellent sources of organic matter.
Building soil organic matter improves soil quality.
Soils typically range from 1 per cent to 10 percent organic matter.
While a higher percentage is usually better, over-application of manure and compost can pollute streams and water bodies,even when the surface water is located far from the garden.
Animal-based composts and manures tend to be high in phosphorus, a nutrient that contributes to water pollution.
If a soil test shows that a soil is very high in phosphorus, soil-building cover crops are a better way to maintain and build organic matter than by adding more composts and manures.
More about soil organic matter
Organic matter: key to soil fertility Explains the importance of organic matter in managing soil fertility.
More information on maintaining your soil's fertility
Test your soil Test every two or three years and follow recommendations for lime and fertilizers; you'll save money and ensure best results.
Understanding your soil test results Fact sheet explains each component of your soil test report.
Fertilizing the organic garden Fact sheet explains what makes a garden "organic" and how organic gardeners maintain their soil's fertility.
Soil Amendments and Fertilizers Explains the differeces between amendments, fertilizers, growth stimulants, and potting mixes; offers lists of each, with descriptions of each product in lists.
