Growth and feed quality of five perennial ryegrass (Lolium perenne L.) cultivars under three water treatments

Abstract

Growth and feed quality of five perennial ryegrass cultivars were compared under three water treatments: non-stress (field capacity, FC), mid-stress (50% FC) and high-stress (30% FC). There were three New Zealand cultivars (Alto, Bronsyn and Trojan), one Morrocan cultivar (Barberia) and one cultivar from Norway (Norway). Water stress reduced dry matter production, leaf water content, leaf width, and leaf photosynthetic rate and stomatal conductance of all cultivars by similar amounts. In contrast, water stress increased feed quality (dry matter digestibility and metabolizable energy) but again with no consistent cultivar effect. Averaged over all cultivars, the magnitude of the reduction in dry matter production (44% under high-stress and 21% under mid-stress) was substantially greater than that of the increase in feed quality (2% under mid-stress and 4% under high-stress for dry matter digestibility, 3% under mid-stress and 5% under high-stress for metabolizable energy). For all cultivars, dry matter production and feed quality returned to normal after rehydration of high water stressed plants. It appears that it will be very difficult to develop a cultivar with maintained growth under water stress conditions. However, against this, perennial ryegrass cultivars in general have a strong ability to recover from drought which is an extremely important characteristic in perennial pastures subject to periodic water stress.