RILL EROSION IN CONTRASTING LANDSCAPES

The data from the national project to monitor water erosion has mostly been treated in an aggregate form, because in many of the monitored transects in any year too few fields were eroded for the data to be split into its component parts. However, in crop year 1983 erosion affected enough fields in two localities with contrasting soils for their data to be compared. Rainfall patterns in the two localities were similar. The transects covered a sandland area in Nottinghamshire and an area of clayland in and on the margins of Bedfordshire. Compared with the clayland, rilling of the sandland was widespread, related to the greater range of crops grown there, and more severe. On clayland, rills were mainly confined to valley floors, and slopes flanking these valleys generally had lower gradients than those on the sandland. On sandland, slopes were steeper in eroded fields drilled to winter cereals than they were in fields planted to potatoes or sugarbeet. Such field-based studies hint at the complex interactions of rain falling on a cropped field. Erosional thresholds are not static. The areas of fields affected by erosion and deposition were mostly very small. This helps us understand why the farmer often considers erosion unimportant.