Compost is the decomposed remains of organic materials-including leaves, kitchen scraps, and plant remains. Compost contains essentially all the major and minor nutrients plants need to thrive and improves soil structure—the home where plants live.
You cannot add too much compost to your vegetable garden—all of the compost you add will improve crop yield. If possible, spread an inch of compost across planting beds in early spring and again after harvest. If you can spread two inches of compost across the planting area, even better! As well, throw a handful of compost into planting holes at transplant time and later add compost around crops during the growing season as a side-dressing for an extra dose of nutrients.
The best compost is aged compost; it will be blackish brown in color, moist, crumbly, and uniform in texture; the vegetable matter in aged compost will not be recognizable. The nutrients in aged compost—often called humus—will be the most accessible to plant roots. (Leaf transpiration draws the nutrients in humus that has been dissolved in soil moisture into plant roots and up into plant cells to fuel plant growth.) Partially decomposed compost benefits the soil as well; it feed earthworms and soil bacteria that exude plant nutrients as well.
Where to get compost
You can make your own compost or you can buy it bagged at your local garden center.
How to make compost
There are two ways to make compost: aerobic composting allows air to accelerate decomposition; anaerobic composting all but excludes air.
Anaerobic composting can be done simply by piling up garden and kitchen waste as it accumulates into one big pile or building a compost pile one layer at a time—alternating brown and green waste. Layering is the most effective way of anaerobic composting. Layers should alternate between woody, carbon-rich material (browns), and lush, leafy nitrogen-rich material (greens). An optimal layer would be about 6 inches deep; the optimal compost pile would be 3 to 4 feet high and wide. Organic material can simply be piled up or held in a box or cage, lightly sprinkled with water, then covered with a tarp or heavy-duty plastic sheet and left to rot. Complete decomposition will occur in 9 months to a year depending upon the weather. (Solar heat will accelerate decomposition.)
Aerobic composting is accomplished via rapid decomposition. Follow the same layer and compost pile formula used in anaerobic composting, but rather than walking away and allowing time to take its course, aerobic composting calls for turning the compost. Turning introduces fresh oxygen into the pile which re-activates the composting process by giving bacteria renewed energy to decompose organic materials. Aerobic composters seek to keep the center of the compost pile at about 140°-158°F, optimal for decomposition. When the temperature falls below optimal (as measured by a compost thermometer), the pile is turned—as often as once a week. You can turn a compost pile by forking materials on the outside of the pile to the center or by breaking down the pile and rebuilding it layer by layer.
What to compost
Compost is best made from garden cuttings and kitchen peelings and scraps, including fruit scraps, vegetable scraps, coffee grounds, stale bread and eggshells. Do not use meat, bones, or fat, including dairy products in compost piles—these materials will not decompose quickly and will attract insects and vermin.
Keep the compost pile just moist; do not allow it to dry out. Aim for about 50 percent greens (grass cuttings and fruit and vegetable scraps) and about 50 percent browns (dry leaves and twigs, egg boxes and cardboard). If the compost turns wet and sludgy, add more browns, if it is too dry, add more greens.