If you’re planting a lawn, a vegetable garden or fruit trees, you may need to add generous amounts of compost to your soil before you plant so that the soil absorbs and holds water more efficiently. If you’re landscaping with native and xeric plants, you probably don’t need to add any organic matter to the soil as these plants prefer lean soils. For arid-adapted plants, usually all you’ll need to do is loosen the soil well before you plant, and water deeply enough to encourage them to root extensively.