Effects of elevated CO2 concentration, supplemental irrigation and nitrogenous fertilizer application on rain-fed spring wheat yield

It is expected that the CO2 concentration of the Earth’s atmosphere will reach 600–1000 ppm by the end of the 21st century. Therefore, in this study, we evaluated the effects of elevated CO2 concentrations on the development of rain-fed spring wheat in an attempt to identify a practical pathway to increase crop production. To accomplish this, a field experiment was conducted at Guyuan Experimental Station in a semiarid region of China during 2005–2007. During this experiment, the CO2 concentration was increased to 40.0 ppm and supplemental irrigation and nitrogenous fertilizer (N fertilizer) were applied. The experimental results showed that the elevated CO2 concentration significantly improved the thousand-grain weight and the grain number per spike. Furthermore, supplemental irrigation and N fertilizer application during the elongation and booting stage of rain-fed spring wheat in conjunction with an elevated CO2 concentration improved the water use efficiency (WUE), nitrogen use efficiency (NUE), thousand-grain weight, and the yield by 14.6%, 39.6%, 9.3%, and 14.7%, respectively, when compared to groups subjected to the same treatment but not grown under elevated CO2 concentrations. Furthermore, the spring wheat yield was improved by 81.8% in response to an elevated CO2 concentration, 60 mm of supplemental irrigation and applied N fertilizer (37.5 g m−2 NH4NO3). However, the presence of an elevated CO2 concentration without supplemental irrigation and N fertilizer only resulted in an increase in the wheat yield of 7.8%. Consequently, the combination of elevated CO2 concentration, supplemental irrigation and N fertilizer application played an important role in the improvement of WUE, NUE, thousand-grain weight, and grain yield of rain-fed spring wheat in this region.