Impact of Increased Atmosphere CO2 Concentration on Crop Yield, Transpiration and Water Productivity of Main Cereals in the Qazvin Plain

Impact of atmosphere CO2 concentration on crop transpiration and photosynthesis is undeniable. In this study, the impact of increased CO2 concentration on wheat, barley and maize, as the main cereals of the Qazvin Plain, was studied under A1B, A2, B1 and B2 scenarios using the calibrated and validated AquaCrop model. Under these scenarios (increased CO2 concentration, unchanged weather data and the assumption of unchanged level of irrigation water supply), average wheat yield will increase between 11.5 and 14.4% for the 2010-2035 period as compared to the 26-year base period (1984-2009). For barley and maize, this average increase will be 8.5 to 11.3% and 3.7 to 4.3%, respectively. Total crop transpiration will decrease on average by 7, 5 and 1% for wheat, barley and maize, respectively. Moreover, increases in water productivity of the studied crops were estimated as 13, 6 and 4% respectively. These results confirm more significant impact of increased atmosphere CO2 concentration on C3 crops (like wheat and barley) as compared with C4 crops (like maize).