Digging in Organic Matter 

Improve the structure of soil by digging in bulky organic matter every year. This is most beneficial on sandy soils, where it helps to retain moisture and nutrients that are otherwise quickly lost. Adding organic matter along with grit to clay soils can help open up the soil structure and improve its sticky texture.

Well-rotted garden compost is a valuable form of organic matter, but well-rotted farmyard manure, spent mushroom compost and green manures are all useful alternatives. During a dry spell in fall or winter, spread a 4- to 6-inch layer of organic matter over the soil and dig it in to a spade's depth. Alternatively, sow a green manure, such as mustard (above), cut it down before it becomes woody, leave to wilt, then dig into the soil.