Effects of grass ley set-aside on runoff, erosion and organic matter levels in sandy soils in East Shropshire, UK

Abstract

Investigations were conducted to assess the potential contribution of grass ley set-aside to soil conservation. Ten runoff plots at the Hilton experimental site, Shropshire, UK, were put to a temporary grass ley in April 1991, to simulate one specific set-aside land use. Plot slope angles varied between 7 and 15°. Runoff and erosion rates over 5 years were low, despite the occurrence of potentially erosive rains. Mean runoff was 0.22% of precipitation (S.D. 0.16, n = 49 plot years), compared with an 11-year mean value of 0.14% on permanent grassland. Erosion rates decreased to tolerable levels once ∼ 30% vegetation cover had established, then rates remained low, despite the occurrence of potentially erosive rains. Under developed ley cover, plot erosion rates were ∼ 0.1−0.5 t ha −1 year −1, with a mean value of 0.23 t ha −1 year −1 (S.D. 0.14) for 49 plot years. Results suggest erosion rates progressively decrease through time, as the ley cover matures. Erosion rate and slope angle were poorly correlated, suggesting leys are highly effective for soil conservation, even on steep slopes. Physical processes of slope wash became inefficient in transporting soil, while plot observations suggest that biological processes became more important, particularly exposure and subsequent erosion of soil from mole hills and worm casts. Mean soil organic matter content increased consistently and significantly on the set-aside plots, by a mean value of 0.39% in 2 years and 0.78% in 4 years. Soil erodibility significantly decreased. Results suggest that using grass leys for set-aside could prove a viable soil conservation technique. Grassland could also be used as ‘soakaways’ in arable systems; braking, filtering and infiltrating runoff, thus decreasing net sediment transfer downslope.