Biomass production and water use efficiency in perennial grasses during and after drought stress

Drought is a great challenge to agricultural production, and cultivation of drought tolerant or water use efficient cultivars is important to ensure high biomass yields for bio-refining and bioenergy. Here we evaluated drought tolerance of four C3 species, Dactylis glomerata cvs. Sevenop and Amba, Festuca arundinacea cvs. Jordane and Kora, Phalaris arundinacea cvs. Bamse and Chieftain and Festulolium pabulare cv. Hykor, and two C4 species Miscanthus × giganteus and M. lutarioriparius. Control (irrigated) and drought treated plants were grown on coarse and loamy sand in 1 m2 lysimeter plots where rain was excluded. Drought periods started after harvest and lasted until 80% of available soil water had been used. Drought caused a decrease in dry matter yield (DM; p<0.001) for all species and cultivars during the drought period. Cultivars Sevenop, Kora and Jordane produced DM at equal levels and higher than the other C3 cultivars in control and drought treated plots both during and after the drought period. Negative correlations were observed between stomatal conductance (gs) and leaf water potential (p<0.01) and positive correlations between gs and DM (p<0.05) indicating that gs might be suitable for assessment of drought stress. There were indications of positive associations between plants carbon isotope composition and water use efficiency (WUE) as well as DM under well-watered conditions. Compared to control, drought treated plots showed increased growth in the period after drought stress. Thus, the drought events did not affect total biomass production (DMtotal) of the whole growing season. During drought stress and the whole growing season, WUE was higher in drought treated compared to control plots, so it seems possible to save water without loss of biomass. Across soil types M. lutarioriparius had the highest DMtotal (15.0 t ha−1), WUEtotal (3.6 g l−1) and radiation use efficiency (2.3 g MJ−1) of the evaluated grasses. This article is protected by copyright. All rights reserved.