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Metadata onlyThe contribution of ryegrass (Lolium perenne) ley set-aside to soil conservation and soil organic matter (SOM) content was investigated. Ten runoff plots (7–15°, 12–27% slope) at the Hilton Experimental Site, Shropshire, UK, were put to a grass ley in April 1991. Runoff and erosion rates during 9 years were low, despite the occurrence of potentially erosive rains. Mean runoff was 0.24 ± 0.20% (±S.D.) of precipitation (n = 89 plot-years), compared with a 15-year mean value of 0.13 ± 0.04% on permanent (control) grassland. Mean erosion rate was 0.21 ± 0.14 t ha−1 year−1 (n = 69 plot-years). Erosion rate and slope were poorly correlated, suggesting leys are highly effective for soil conservation. Mean SOM content increased consistently and significantly on the set-aside plots from 20.4 g kg−1 in 1991 to 31.1 g kg−1 in 2001. Contrary to the usually strong relationship between SOM and clay content, the percentage silt exhibited a stronger correlation with SOM than percentage clay content. Furthermore, there were equally strong correlations between SOM and cumulative particle size fractions of both clay and silt contents. In the absence of significant quantities of clay in these sandy soils, silts assist binding of SOM, which has significance for assessing soil carbon sequestration potential

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Seven case studies are presented, demonstrating the successful use of a laboratory-based drip-screen rainfall simulator at Coventry University to investigate several hydrological, pedological and geomorphological problems. The results of previously unpublished studies are presented in full, while the salient points of published studies are discussed. Synthesis of the experimental results led to the recognition of various philosophical and practical problems associated with the realistic simulation of rain, which need to be addressed in future research. Particular problems are posed by the variety of analytical approaches and simulator designs, as they impede meaningful inter-laboratory comparisons. It is argued that future improvements require optimization, harmonization and standardization of analytical procedures and rainfall simulators. An ideal approach would be the development of a European key laboratory to offer realistic and standardized simulation conditions.

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