Soils become acid naturally in humid climates.
Rainfall, over time, leaches out the basic minerals in soils. Fertilizers and organic matter from manure and compost tend to speed up this process. Plant nutrients such as calcium and magnesium may be deficient in acid soils. Beneficial soil bacteria that fix nitrogen on the roots of legumes such as beans and peas cannot survive in acid soils. Most Alabama garden soils will require liming every 3 to 5 years to maintain the soil pH between 5.5 to 6.5.