A band in the bottom of a row trench or several shovels-full of compost can be added to the bottom of planting holes. This is especially true of singly planted tomato plants, perennial flowers, or trees or shrubs. As a general rule, mix equal parts of compost and water. The left over compost can be later added to garden soil. Mulches hold moisture in the soil, prevent weed growth, and reduce soil crusting and splashing.
Mulches also help to keep the soil cooler in hot summer conditions.
A layer of compost 2-3 inches thick along the row of garden vegetables or flowers or spread around perennial flowers, trees or shrubs reduces the moisture fluctuations and reduces evaporation of water from the soil surface. After the garden season, simply till the mulch into the soil as a source of organic material. The benefits of composting certainly outweigh the limitations. It certainly is possible, however, to over-do applications of compost. The high nutrient content of some composts may provide too much of nutrient if excessive applications are made.