14 February 2014
Soil for Gardeners
It is important for the gardener to know what type of soil he has in his garden or allotment, so the following is a brief guide to the six main soil types and how to identify them.
Clay is made up of particles less than 0.002mm in size, and clay soils are considered to contain over 25% clay.
Sand comprises of articles between 0.05 and 2.00mm and sandy soils are made up of mainly sand with little clay.
Silt soils fit inbetween the clay and sandy soils with a particle size between 0.002 and 0.05mm.
Loams are the ideal soil for most purposes, as they provide a good balance of all soil particle types.
Certain areas of the country have chalky soils, as a result of the underlying rock. Chalk soils are alkaline and are unsuitable for acid-loving plants, so choose plants that like alkaline conditions.
Peat soils are more likely to be found in farmland rather than gardens, and are unlikely to be a problem for most gardeners.
The best way to tell what type of soil you have is by it's feel and by rolling it in your hands.
Sandy soil feels gritty as you can feel sand grains within it, and it falls through your fingers. It won't stick together if you roll it in your hand unless it is perhaps a sandy loam, in which case the clay element of the soil will make it more cohesive.
Clay soil can be easily rolled into a long thin sausage as it is very cohesive. Heavy clay can be smoothed to a shiny finish by rubbing with a finger, though lighter clays won’t get quite as shiny. Clay tends to be sticky when wet.
You won't usually find a pure silt soil in your garden, as they usually occur in the form of a silty sand or silty clay. Pure silts have a slightly soapy, slippery texture, and do not stick together easily.
If soil froths when placed in a jar of vinegar, then it contains chalk or limestone and is lime rich.
Another aspect of your soil that you will benefit from knowing is it's pH, which is a measure of it's acidity or alkalinity. This is important as plants frequently prefer one type of soil to another, so the soil's pH will affect the type of plants you can grow.
Acid soils have a pH between 1 and 7, e.g. peaty soil
Neutral soils have a pH of exactly 7, e.g. some clay soils
Alkaline soils have a pH between 7 and 14, e.g. chalky soil
Most soils in the UK have a pH between pH 4.0 and 8.5 while most plants prefer a pH of 6.5 to 7. Rhododendrons are one of the plants which need acid soil, whereas saxifrages are the opposite, needing an alkaline soil.
You can buy a pH testing kit at your local garden centre or online for a small outlay - just follow the instructions to obtain the magic number. You can now plan your garden scientifically!