 The reason seems to be that this plastic film keeps the humidity in the topsoil and increases the temperature.Miscanthus is close to the theoretical maximum efficiency at turning solar radiation into biomass,
and its water use efficiency is among the highest of any crop.It has twice the water use efficiency of its fellow C4 plant maize, twice the efficiency as the C3 energy crop willow ("Salix viminalis"), and four times the efficiency as the C3 plant wheat.