Chemical fertilizer input was the key factor affecting soil ecological environment and land productivity in a small watershed.Wangdonggou watershed is just the type of gully region on the Loess Plateau.The monitoring of chemical fertilizer input,land use change and land pro-ductivity started in the small watershed in1984.NO₃^--N accumulation in soil profiles of0～300cm was determined in croplands with continuous and rotation cropping systems,apple yard with7-and15-years of apple trees as well as fallow land in the small watershed.Fertilizer input,NO₃^--N accumulation,and land use structure were analyzed in the small watershed.The results showed that chemical fertilizer led to significant increase in land productivity and decrease in the area of cropland.Chemical fertilizer input was an important driver to land use structure change,the area of apple yard land increased significantly from1984to1995.Changes in land use structure further affected input of chemical fertilizer into the small watershed.NO₃^--N accu-mulation in soil depth of100～200cm has been significantly produced in cropland and apple yard land under current conventional fertilization practices.NO₃^--N accumulation in apple yard land was greater than that in cropland.NO₃^--N accumulation in continuous cropping systems was greater than that in rotational cropping systems.NO₃^--N accumulation was obviously related to fertilizer input,fertilizer uptake by crops,and soil moisture change in the small watershed.