Important Factors Regarding Soil
Big words soil scientists use, and why they might matter to you
So, you really want to understand soil, huh? Well, we can't offer you a degree in soil science, but we will define a few soil factors in basic terms to get you off on the right foot. Here are a few important factors to keep in mind.
Bulk Density: How heavy the soil is. In general, you want your soil to be light, but if it is too light the plant will topple over, and that's just silly.
Friability: This has to do with texture. It must be easy for the roots to move through the soil. If you can stick your finger into it, then roots can grow through it easily.
Water-holding capacity: How well your soil can hold onto water. Remember, you want your soil to dry out between waterings so the roots can breathe. If your soil is too good at holding water, it will never dry out, and your plants may suffer - in other words, rot.
Air-filled pore space: 10 to 15% of your soil mix should be air. Materials like Perlite and shredded bark are chunky enough to create air space, letting the roots have oxygen, even when the soil is wet.
Nutrient-holding capacity: Certain soils and soil mixtures are able to hold onto the nutrients better than others.
Absorbency: How well your growing medium takes in water. Some materials, such as peat, are quite water repellent and should be moistened before planting and not allowed to dry out completely.
Granule Size: Fine particles, the small stuff in the bottom of the bag, will fill up all those air pores and water pores you've worked so hard for. Don't buy a bag with lots of fines, and don't empty that last bit of finely ground material into your pots.
Wetting agents: Not a bad idea if you are in a very windy spot, won't be watering as often as you should, or are using a blend with more than 50% Sphagnum peatmoss.
Human factors affecting soil performance: What soil blend you chose, how you mix it, container size, watering habits and your attitude will all affect how well your soil performs.
Knowing these things will ultimately make you a more educated consumer when deciding what soil mix is right for you and your plants. But, if the terms are too much for you to digest, fear not - most commercial potting mixes will work for most plants.