Dynamics of Soil Nutrients during Natural Recovery Process of Abandoned Farmland in Huailai Basin,Hebei Province

Dynamics of soil nutrients during the natural restoration process of farmland were studied with the method of substituting time with space.Three tracts of sample fields were selected to represent three different phases of the restoration process,initial period of deserted farmland,grassland,and shrub land.Soil samples from different profile depths were collected and analyzed for soil organic matter,total nutrients and readily available nutrients.Results showed that responses to the recovery process were obviously different between the total nutrient and its corresponding available one.Soil organic matter increased with the process of the restoration.The P and K circulation shifted from under physical control to under biological control step by step,but available P increased slowly in the early stage.Available N increased after an initial decrease at the beginning.As for total nutrients,only total N showed an increasing trend with the restoration process.The deeper rooting of shrubs affected soil organic matter and available nutrients obviously in the deep soil layers.Restoration of vegetation is closely related to increase in soil fertility and this relationship is strengthened with the restoration process.