Infrared Warming Affects Intrarow Soil Carbon Dioxide Efflux during Vegetative Growth of Spring Wheat

Global warming will likely affect carbon cycles in agricultural soils. Our objective was to deploy infrared (IR) warming to characterize the effect of global warming on soil temperature ( T s ), volumetric soil‐water content ( θ s ), and intrarow soil CO 2 efflux ( Φ s ) of an open‐field spring wheat ( Triticum aestivum L. cv. Yecora Rojo) crop grown in the semiarid desert Southwest. A temperature free‐air controlled enhancement (T‐FACE) apparatus using IR heaters maintained canopy air temperature above 3.0‐m plots by 1.3 and 2.7°C (0.2 and 0.3°C below the targeted set‐points) during the diurnal and nocturnal periods, respectively. A randomized complete block (RCB) design with two IR warming treatments (i.e., Heated; Reference) in three replicates was planted on 10 Mar. and 1 Dec. 2008. Intrarow T s , θ s , and Φ s were measured from emergence (bare soil) up until inflorescence emergence (canopy closure). Under ample soil water supply with high θ s , midday Φ s was 10% greater in Heated [4.1 μmol (CO 2 ) m −2 s −1 ] compared with Reference [3.7 μmol (CO 2 ) m −2 s −1 ]. In contrast, as the soil dried and θ s decreased to a greater degree in Heated compared with Reference, a 10% decrease in Φ s occurred in Heated compared with Reference. Overall, θ s had the greatest impact on Φ s , whereas it was responsive to T s only under high θ s. Accurate predictions of global climate change effects on Φ s in agricultural soils require that interactive effects of T s and θ s be coupled. Infrared warming with T‐FACE proved to be an effective experimental methodology to investigate these interactive effects.