Composition: 100% Mushroom Compost Uses: When added to site soil Mushroom Compost improves drainage in heavy soils, reduces moisture evaporation and will help to retain moisture in sandy soils. Must be mixed into existing soils for best results. Installation: Spread over your garden beds or existing site soil to a depth of 50mm to 100mm and incorporate into the first 150mm to 200mm of your garden bed.