The use of liming materials on acid soils to supply available calcium and correct soil acidity long has been regarded as a basic principle in the Iowa system of soil management. The beneficial effects are associated primarily with the efficient production of legumes in various cropping systems, thereby contributing to the maintenance of soil fertility and conservation of the soil resources. Many of the important agricultural soils in Iowa were originally well supplied with lime, but through leaching, erosion, decomposition processes, removal by crops and the sale of livestock products there has been a gradual tendency for them to become acid.