Is UK biofuel supply from Miscanthus water-limited?

Sustainable Miscanthus plantings encouraged under publicly funded schemes should be based oil sound economic and environmental assessments. We developed in empirical yield model for Miscanthus from harvestable dry matter yields at 14 field trials in the UK to estimate site-specific and regional yields derived front meteorological variables and soil available Water. Harvestable yields of crops established for at least 3 years at 14 arable sites across the UK ranged from 5 to 18 t/ha, averaging at 12.8 (+/- 2.9) t/ha. Variables considered to affect yield were number of years after plantings length of season (T-air > 9 degrees C), temperature. global solar radiation, precipitation and potential evapotranspiration during the season, and soil available water capacity (AWC). At a single site (Rothamsted), AWC and the relative average potential soil moisture deficit during the main growing season explained 70% of annual yield variation (RMSE = 1.38 t/ha, P < 0.001). F or the complete UK data set (n = 67) yield variation was related to A WC, air temperature and precipitation (RMSE = 2.1 t/ha, P < 0.01). Linking soil Survey and spatially interpolated weather data we calculated an overall national average dry matter yield of 9.6 t/ha. As shown for two counties (Oxfordshire and North Yorkshire), estimated yield may decrease by 1 t/ha, and its uncertainty may rise from 15 to > 20%, when soil survey instead of local soil data are used. Using data from a single weather station can introduce a bias (< I t/ha) because of differences in elevation and local temperature and precipitation. Overall. it seems most important for bioenergy plantings to assure Sufficient Water supply from the soil (AWC > 150 mm) during the main growing season.