In the eastern and southern China boron-deficient soils have been found in large areas,while soils in the arid regions are rather rich in boron.The amount of boron in soils varies with parent materials.Soils derived from shale,limestone,and marine sediment are usually rich in boron and those derived from granite and other igneous rocks,gneiss and sandstone are low in boron.Strong alkalinity and rich organic matter in soils reduce the availability of soil boron.Thus the boron-deficient soils may be divided into two types and four subtypes.