It's not often we re-publish other peoples blog posts, but when I was thinking of writing a post about 'Soil Improvement', an enormous subject at the best of times, I started to do some research and came across this wonderful article in Gardeners World. Simply titled 'How to improve your soil' it was such an easy, informative read, I'll just re-publish it, because I can't do any better.
I'll just give you the soil improvement preamble and then link to the article and the author:
Plants need good soil conditions if they are to give the best results. Improving the soil with plenty of organic matter in the form of compost helps drainage and aeration on heavy soils and conserves essential moisture on light ones.