EFFECTS OF CHANGES IN TEMPERATURE AND CO2 CONCENTRATION ON SIMULATED SPRING WHEAT YIELDS IN THE NETHERLANDS

A crop growth simulation model based on SUCROS87 was constructed to study the effects of temperature rise and increase of the atmospheric CO2 concentration on spring wheat yields iii The Netherlands. The model simulated potential production (limited by crop characteristics, temperature and radiation but without any stress from water or nutrient shortages or pests, diseases and weeds) and water-limited production in which growth is also limited by water shortage. The model was validated for the present climatic conditions. When daily weather data from a nearby station were used, the model was well able to simulate yields obtained in field experiments. Effects of several combinations of temperature rise and atmospheric CO2 concentration on simulated yields were studied. A temperature rise resulted in a reduction in simulated yield due to shortening of the growing period. Large variations existed in the magnitude of this reduction. Increases in atmospheric CO2 concentration led to yield increases due to higher assimilation rates and to increase of the water use efficiency. Combination of temperature rise and higher CO2 concentration resulted in small yield increases in years in which water was not limiting growth and large yield increases in dry years. Change of variety or of sowing date could not reduce the negative effects of temperature rise on simulated yields.