Russell W. Gesch and Jane M-F Johnson, USDA-ARS, Morris, MN
Double-cropping winter camelina (Camelina sativa) followed by soybean (Glycine max) may increase land use efficiency by producing food and biofuel in a single season and is a viable cropping system for the northern Corn Belt. However, regional success of double-cropping, especially under dryland conditions, is highly dependent on water use (i.e., having enough water to produce both crops). A 2-yr field study was conducted in western Minnesota to determine seasonal water use in winter camelina – soybean double crop systems compared to a full-season soybean crop. Different methods of sequential double-cropping and relay-cropping were evaluated. Additionally, rooting depth and density of camelina at early reproductive phase were evaluated to a soil depth of 1 m. Water use (spring to final harvest) varied little between double crop treatments but as expected was greater than the single full-season soybean. However, the difference was relatively small, largely due to the short lifecycle of camelina. Water use in the double crop systems was only about 21-25 mm greater than the full-season soybean in yr-1 and 40-60 mm greater in yr-2. About 80% of camelina’s root mass was within the surface to 30 cm depth and only around 5% within the 60-100 cm depth. Results also indicated that about 20-30% of camelina’s biomass is belowground. Although seasonal water use for double-cropping winter camelina and soybean was greater than a single full-season soybean crop, results indicate that it may be a suitable system for many dryland cropping areas in the Corn Belt.