Ferretti says soil test kits are available for a nominal fee at Penn State Cooperative Extension county offices, as well as many garden centers. He explains that soil test results will tell homeowners if their soil is acidic, with a pH of 5.8 or lower, or alkaline, with a pH of 7.2 or higher. If it's alkaline, the soil can be acidified by adding iron sulfate, powdered sulfur or aluminum sulfate. Carefully follow the directions for sulfates. Applications should be higher in fall and lower in spring.
Many organic gardeners prefer to use manures instead of chemical fertilizers.
Ferretti warns gardeners never to apply manure after crops have been planted. If you use manure, it should always be applied the previous fall, to give it a chance to break down within the soil. In years past, soil tests offered three separate fertilization recommendations, depending on the type of crops to be planted. Most labs today, including Penn State's, offer a single mid-range soil amendment. Cabbage and related crops, tomatoes, sweet corn, beets, carrots, onions, celery and potatoes.