Can we beat the heat in southern Australian dairy pastures?

Heat waves are forecast to increasingly challenge home-grown feed production in southern Australian dairy regions. This is due to 60-70% of the dairy cow’s diet being derived from perennial ryegrass (Lolium perenne L.), which has a low tolerance to high temperatures (>30˚C). There is a need to identify temperate perennial forage species that are better adapted to heat wave conditions. To address this research objective a controlled environment study was undertaken to compare the responses of ten perennial forage species to optimal and heat wave temperature regimes (day/night temperatures of 23/14˚C and 38/26˚C). The effect of soil moisture availability (optimal watering or no water) and the recovery capacity of plants grown in optimal conditions (day/night temperature regime of 24/18˚C; optimal watering) for 18 d after temperature treatments ceased were also examined. Chicory (Cichorium intybus L., cv. Grasslands Puna) proved most tolerant, evidenced by its’ capacity unlike perennial ryegrass (cv. Samson) to recover from exposure to heat stress and soil moisture deficit applied for 18 d (Fig. 1). Results suggest that chicory may enable producers to resume production more rapidly following an extended heat wave, than possible with perennial ryegrass under dryland conditions. Further research is planned to determine the effects of grazing management and input use on the heat wave tolerance of chicory. Data collected will be used to develop parameters in biophysical models to evaluate the long-term performance of chicory in different agro-climatic regions, both now and under future climate scenarios.