Manganese deficiency has been a problem in agricultural practice in many soils in North China and manganese fertilizer also has been extensively used to correct the problem.In order to further understand behavior of manganese fertilizer in soils,a long-term field experiment was initiated in 1984 on continuous application of manganese fertilizer in dryland soils of the Loess Plateau.After 17 years,availability and fractions of manganese in the soil were investigated using a modified sequential extraction technique.The results showed that total manganese and DTPA extractable manganese were not increased much in the soil.But the latter did show an increasing trend with the time,no matter manganese fertilizer was added or not.In addition,the application of manganese fertilizer contributed little to increase of soil DTPA-Mn,which ranged from 0.4 to 1.7 mg kg^-1.Manganese fractions in all studied soils were greater in manganese fertilizer treatments compared with those in control.It was also found that mineral bonded manganese occupied about 87.3%~91.8% of the total soil manganese,while carbonate form and oxides form of manganese,and organic matter strongly bonded manganese shared similar percentages.In terms of content,the various fractions of manganese ranked in the order of mineral bonded>carbonate bonded>oxides bonded>organic matter strongly bonded>organic matter weakly bonded>exchangeable.About 91.1%~98.6% of fertilizer manganese was in the form of carbonate bonded,oxide bonded,or organic matter strongly bonded manganese,or in the mineral form,which were not readily available for the crop to use.Only 1.4%~8.8% of fertilizer manganese entered into exchangeable and organic matter weakly bonded forms,which were considered as available manganese in soils.The results of statistical analysis showed that exchangeable and organic matter weakly bonded manganese were the major sources of soil available manganese,carbonate bonded and organic matter strongly bonded manganese made little contribution to soil available manganese.