Mulching Using a mulch in your backyard garden improves the soil by releasing nitrogen, minerals, and other nutrients for plant use as it decays. Also, mulches prevent loss of moisture from the soil by evaporation. Sun and wind hasten the loss of moisture, and this will quickly be reflected in higher water bills. A mulch of partially rotted straw, compost, or other undecomposed crop residue on the soil not only retards this water loss from the soil, but also helps keep the soil surface from crusting and keeps weeds from growing. If an occasional weed pokes through the soil, it is easily pulled out.
Mulches keep the soil from overheating when summer temperatures rise.
Many vegetable plants thrive in hot weather but need a cool surface soil. Mulches add organic matter to the soil and furnish food for earthworms which are valuable in aerating the soil. The organic matter helps to keep the soil crumbly and easy to work. At the end of the growing season, the mulch can be worked into the soil to supply organic matter the following year. Many organic materials such as straw and autumn leaves are rich in carbohydrates but low in nitrogen.