Is your soil deep enough? This is an important factor that can be over looked. We might take it for granted that the soil we are looking at has sufficient depth. It has to be checked with a spade to know for sure.
Dig test holes to check that you have at least 14 inches (350 mm) top soil. If you hit rock, rubble or sub-soil at 6 inches (150 mm) you will need to import top soil.
How to know your Soil Quality ?
Does water drain through your soil?
If you empty a bucket of water over your garden will the water stand or drain. If a puddle remains after several minutes your soil may be compact; like a footpath.
Deep cultivation and agricultural drains are a remedy. Soil has to be free draining to grow crops.
Is it toxic?
I f plants die in your soil for no apparent reason you can test toxicity. Take a sample and grow cress in it on a window sill. Cress may germinate but die suddenly if the soil contains diesel, salt or residual herbicide.
Soil Acidity PH
pH is a measure of acid or alkaline soil. Most plants require a neutral pH of 7. Some plants are ericaceous which means they prefer a low or acid pH of 5. Lime loving plants are the opposite and need higher than neutral ph.
You can buy pH test kits from most garden suppliers. Kitchen gardens mostly need pH of 7. You can influence the pH of your soil. If it is too acid add lime. If it is too alkaline use sulphur based fertiliser.
Soil Type ?
Soil type can affect soil quality. Sandy soils contain little nutrient where clay soils retain nutrient. A high clay content within your soil can be observed using a simple test.
Role the soil in your hands and try and make a ball; if the soil sticks together then the soil contains clay. Soil that runs through your fingers or contains coarse particles will be sandy soil.
There can be millions of worms living under an ordinary sized garden that has good soil. Earthworms aerate deep into the ground they place casts that are rich in trace elements. Composting worms live on the surface if leaf litter is available.
You can test for worms by counting them at the same time as you dig holes to see how deep your top soil is.
Organic matter is broken down by soil organisms. It becomes dark in color and sits between the soil particles. We call it humus; this separates the particles and creates space between them that contains air. Humus retains moisture and nutrient.
It mitigates extreme temperatures. In hot conditions the air space allows heat to escape. Humus adsorbs the suns heat; warming the soil during the coldest periods.
How Improve Quality of your soil ?
You can improve the quality of your soil by adding organic matter; farm yard manure or compost. Organic matter brings life to the soil. Beneficial bacteria, worms and many other creatures need decaying material for food and habitat.
In return bacteria fix nutrients into solutions the plants can use. Ground beetles and ladybirds predate aphids. Bio diversity within your soil is the first level of many food chains.
Birds, bats, toads, shrews, and hedgehogs that frequent your garden leave piles of nutrition behind but also eat slugs and snails that are crop pests.
Your soil is good if it sustains bio diversity while providing you with food and ornamental crops.