Compost's real contribution is conditioning the soil so fertilizers and nutrients can be synthesized by microorganisms, and therefore by plants. Compost is to soil as regular exercise is to humans. Compost does have fertilizing properties. That's why, in addition to compost, it is important to enrich soil with the three macro nutrients. Synthetic sources of these nutrients, sold under many brand names and dozens of formulations, should be applied only at specific times, because each type fills a particular need.
Organic fertilizers improve the soil composition with nutrients and minerals.
They help maintain the microorganisms that break down, digest and change soil ingredients to make them usable by plants. The most effective organic fertilizing program should continue year-round. To boost all three major nutrients, the gardener can seek out an all- purpose organic fertilizer mix. A good rule of thumb offered by the scientists at the Rodale Research Center in Emmaus, Pa., is to avoid any mix that contains NPK components adding up to more than 15. A fertilizer with a nitrogen number of 12, for instance, should contain little or none of the other two ingredients to meet the Rodale standard.