Water Use in Camelina–Soybean Dual Cropping Systems

Global population growth is increasing the demand for food, feed, fiber, and fuel. Recently, we reported that winter camelina (Camelina sativa L.) can be feasibly double‐ (DC) and relay‐cropped with soybean [Glycine max (L.) Merr.] in the northern Corn Belt region as an option for sustainably intensified crop production. However, water availability can be a limiting factor for dual crop systems. Therefore, the present study determined seasonal water use in various winter camelina–soybean dual crop systems that included two sequential DC and two relay‐crop treatments compared with a full‐season monocropped soybean (Mono‐Soy). The rooting characteristics of camelina were also evaluated. The study was conducted on a Barnes loam soil (fine‐loamy, mixed, superactive, frigid Calcic Hapludoll) in west central Minnesota over two growing seasons in 2010 and 2011. Camelina had a meager root system with 82% of its root density found in the top 0.3 m of soil. Although both DC and relay‐crop treatments used more seasonal water than a sole soybean crop, on average it was only 26 and 50 mm greater in 2010 and 2011, respectively. Camelina is a low water user compared with soybean. Total cropping system water use efficiency for relay‐cropping was comparable to the sole soybean crop, but for the DC treatments was less. This cropping strategy is a way to sustainably integrate food and fuel production to meet societal needs of a growing population. Moreover, our results indicate that it may be amenable to most rainfed‐farming areas in the upper Midwest where soybean is grown.