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.