Healthy soil holds water in the root zone where plants most need it. Healthy soil needs organic matter (mulch, compost, manure, grass clippings). Worms break this down to make food for plants and their burrows allow air into the soil so the plant roots can breath.
Organic matter needs to be replaced regularly as the worms eat it and plants absorb the nutrients. If organic matter is not added, soil can become like concrete in the summer and turn into a sticky mess in the winter.
Generally soils fall into three main structural types based on the size of grains – clay, loam and sand. The water holding capacity of a soil directly relates to the soil type.
Clay soils
- Retain or hold nutrients and water
- May have poor drainage
- May have low aeration
- May be difficult to cultivate, but not always
If you have clay soil, adding organic matter will improve it and you may want to add gypsum to help break it up. This not helps water gets in more easily, it also breaks up the crust that often forms and means water runs off the surface rather than soaks in.
Sandy soils
- May have little organic matter
- Allow rapid infiltration and drainage of water
- Hold little water or nutrients
- Easy to cultivate
Sandy soils benefit greatly from the introduction of organic matter.
Loam soils
- Thought to be ideal for growing pants
- Drain freely
- Hold moderate amounts of nutrients and water, but not always
Well-structured clays and sandy loams with lots of organic matter are the best soils for holding the largest amounts of water for plant growth.
Soil Improvement Tips
- To improve your soil you need to know what type of soil you have. If you are not sure take a sample to your local garden center and they should be able to inform you of your soil type.
- Don’t cultivate your soil unless it is very compacted after building works. Over-digging destroys the soil structure, therefore destroying the air holes and drainage spaces. This creates a ‘cloddy’ soil that is hard to work.
More Information
The Natural Gardener by Jeffrey Hodges
Gardening Down-Under by Kevin Handreck