Considering the benefits of compost, the only complaint most home composters have about it is that they never seem to have enough.
Spreading a 1/2-inch layer as a topdressing on a 5,000-square-foot lawn requires around 200 cubic feet of compost. It would take several large bins filled to the top to produce that amount of finished compost. Most people will never be able to make that much compost in a season even if they reduce their yard waste close to zero. For that reason, prioritizing the use of the compost supply is important.
How Much to Use
Most books and articles dealing with compost simply advise you to spread the material around a garden bed or plant. They seldom offer any guidance on how thick the layer should be. As a result, most people waste their compost by spreading it too thick. Unless you’re relying on compost as a fertilizer, spread no more than 1 inch. A thicker layer doesn’t harm the soil, but it does limit the total area that can be improved.
If your supply of compost is severely limited, consider stretching it by mixing it with an equal amount of dried leaves, municipal compost, or other organic materials available locally. Compost doesn’t last forever once it’s in the soil. It continues to decompose as microbial action converts it into plant nutrients, so eventually the percentage of organic matter in the soil begins to decline. In northern climates, compost is mostly decomposed after two years in the soil. In southern climates, compost disappears even faster and should be replenished every year.
Where to Use Compost
Deciding where to use your compost should be based on how much you have. If you have a limited amount, then you’ll want to make sure you get the greatest impact from it. For those lucky enough to have a large supply, prioritizing its use isn’t as important.
Since compost builds good soil, the first priority for a limited supply is probably an area where the soil quality needs the most attention. Is that area the highly visible flower bed in the front of the house? Is it the vegetable garden because the size and quality of the harvest are important? Is it a prized tree or shrub?