植生帯を用いた畑地土壌の流出負荷制御

抄録

The effect of grass strips on the reduction of sediment and eutrophic salt loads is been widely recognized. However, there is very little knowledge of the effect of grass strips on the reduction of sediment and eutrophic salt losses. Attention was hence focused on the investigation of what grass strips should be managed. Soil suspension was supplied to the experimental plots under simulated rainfall. During the experiment, surface discharge and sediment concentration were measured. In order to observe the effect of grass strips on the reduction of sediment loss, the difference between the amounts of sediment supplied and sediment loss was investigated in each plot. While the sediment concentration and load from the bare upland field exceeded the concentration and load of the soil suspension supplied, the sediment concentration and load from all the grass strips were lower than the concentration and load of the supplied soil suspension. The difference between the sediment supplied and the sediment loss from the cutting weeds plot for pest control was approximately equivalent to that of the plot with the natural weeds. Therefore, it was concluded that cutting weeds for pest control can be applied to the grass strip for reduction of the sediment loss. There was little difference between the reduction of the sediment loss from the plot with 800 stems/m2 and that from the plot with 1,480 stems/m2 of Tall Fescue [F. arundinacea). However the plot with 2,330 stems/m2 of Tall Fescue was effective for the reduction of sediment loss comparing with 800 stems/m2 and 1,480 stems/m2. It suggests that stem density for grass strips should be maintain 2,330 stems/m2 to control soil loss from upland field.