Farm Table says:
What is the problem?
A warmer and potentially drier future climate is likely to influence the production of forage crops on dairy farms in the southeast dairy regions of Australia. Biophysical modeling was undertaken to explore the resilience of forage production of individual forage crops to scalar increases in temperature, atmospheric carbon dioxide (CO2) concentration and changes in daily rainfall. The APSIM model was used to reflect species-specific responses to growth under elevated atmospheric CO2 concentrations.
What did the research involve?
The model APSIM is used to simulate 40 years of production of forage wheat, oats, annual ryegrass, maize grown for silage, forage sorghum, forage rape and alfalfa grown at three locations in southeast Australia with increased temperature scenarios (1, 2, 3 and 4 °C of warming) and atmospheric CO2 concentration (435, 535, 640 and 750 ppm) and decreasing rainfall scenarios (10, 20 or 30% less rainfall).
What were the key findings?
At all locations positive increases in DM yield compared with the baseline climate scenario were predicted for lucerne (2·6–93·2% increase), wheat (8·9–37·4% increase), oats (6·1–35·9% increase) and annual ryegrass (9·7–66·7% increase) under all future climate scenarios. The response of forage rape and forage sorghum varied between location and climate change scenario. At all locations, maize was predicted to have a minimal change in yield under all future climates (between a 2·6% increase and a 6·8% decrease). The future climate scenarios altered the seasonal pattern of forage supply for wheat, oats, and Lucerne with an increase in forage produced during winter.
Overall the forage crop species examined in the current study with the exception of forage sorghum and forage rape showed resilience to potential future changes in climate with either an increase in yield with increasing temperature and atmospheric CO2 concentrations and either no change or a minimal decrease in DM yield with decreasing rainfall. Forage sorghum yield decreased with a 10% or greater reduction in rainfall while forage rape yield decreased with a 30% decrease in rainfall. Consequently, it can be concluded that annual forage crops examined in the current study will remain viable forage options for the southeastern Australian dairy regions into the future. However, before this conclusion is accepted the underlying assumptions within the model should be considered. As part of the study, parameters were developed to describe the species-specific adaptation to increasing atmospheric CO2 concentrations, namely the responses of crop transpiration efficiency and crop tissue N concentration.