What is the best way to improve soil which consists mostly of clay? – Adrian Higgins, the Washiington Post Garden Editor suggests: “Tilling or digging in compost is an instant way of fixing clay soil, adding leaf mulch successively is a way of doing it over two or three years without starting afresh and having to dig up plants. Worms and other creatures will break down the top layer and begin to incorporate it into the top few inches of earth.”