Garden soils can be silt, sandy or clay based. (There are other types of garden soil as well, but these are a good starting point)
The great 'diarist' - John Evelyn - wrote in 1675...That in his opinion, there were no less than 179,001,060 different types of earth........! Time is short, so forgive me if I only mention a few!
are normally referred to as being one of three basic 'soil structure' groups; Sandy soil, Clay soil and Loam.. This is just the start, but it is a good starting point, for each of these groups tell us much about the garden soil, and what - if anything - needs to be done to improve it.
The one thing above all I have personally found, is that encouraging a good earthworm population in your soil will improve all your other efforts hugely. This is admirably carried out by the use of sphagnum peat or other organic material.
A simple test for your garden soil, is to simply grab a fist-full of moist garden soil, clench it and if it breaks open on releasing, it is likely NOT to be a clay soil - possibly sandy or loam type soil. You can take this test further by rubbing some wet soil between finger and thumb. Clay soil feels silky and sticky, sandy soils will feel coarse.
taking that a step further, the easiest way to find which structure group your garden soil is in, is by testing it in an old coffee jar - take the label off as you will need to see through it. (I'm sure that there are many other jars suited to this job; I happen to drink a lot of coffee!)
This is a great way to get the kids involved - they can even do it for you!
This is What You Do! Let's assume that you garden soil looks the same in all parts of the garden, and the soil seems to be roughly the same sort of texture to the full depth of a garden spade.
Take a couple of typical (!) spoonful; break it up as much as you can, then place it in the jar - just under half a jar full is ideal. Fill the jar with water to within a cm of the top and give it a really good shake (Make sure that the lid is on!) Keep shaking until all of the soil has 'dissolved' and you just have a murky-looking liquid. Leave the jar somewhere to let the contents settle; this will take a few hours.
You should now have several layers of 'soil' types in your jar. At the bottom will be the stone/sand layer, then a 'silt/clay layer, followed by an organic layer. Right at the top the will be a settling of clay. (The cloudy water is in fact a solution of clay particles.) From largest to smallest, the particles are... stones, sand, silt, clay. The one we have missed (organic) can come in all sizes! From the finest humus particles, right up to dead things!
The stone, sand, silt and clay elements are all mineral (in-organic). The organic content is made up of the 'remnants' of things that once lived. If it lived (Animal or Vegetable), and it is now dead, then for the purpose of this article, it is now the 'organic' content of your soil. (There are -should be - living things in your soil. These are not part of your soil's organic matter! Another section for this).
The mineral bits that you can actually see individually, are sand particles. You will need a microscope to see the individual particles of silt, and the smaller individual clay particles can only be seen with an electron microscope! Whatever your soil group, it will have all three mineral particle sizes in it. The ratio of these particles, determines your soil group.
A clay - or silt - soil if you have more of those particles in it than sandy particles. If you rub it between finger and thumb when wet, a 'silt soil' will have a light smooth feel, but won't shine. The finer 'clay soil' will shine and feel sticky. If the soil feels rough to varying degrees, then you have a sandy soil. It could be coarse sand soil, with larger, rougher particles or smooth sand soil, with smaller, softer particles.
If your 'test' reveals more or less equal portions of sand, silt and clay, then you are blessed with the ultimate (generally speaking) A 'loam soil'.
The organic content of the soil is also very important. You can also change the organic content of the soil quite easily. You cannot change the soil structure group very easily. If is is 'clay' it will remain clay - unless you take some very, very drastic measures.
You can improve a clay soil: You can improve a sandy soil: But it will still remain clay or sandy!