Double and Relay Cropping Systems of Oilseed and Biomass Crops for Sustainable Energy Production.

In a growing developing world innovative sustainable cropping systems are necessary to obtain continuous supply of food, feed and energy products. Double and relay cropping systems are an option to produce biofuels, food and forage in a single season on the same land without sacrificing food security. Field studies were conducted between 2012 and 2013 in Prosper and Carrington, North Dakota and Morris, Minnesota. Evaluation of 11 crop sequences of double-cropping and relay-cropping of soybean (Glycine max L.), corn (Zea mays L.), and forage sorghum (Sorghum bicolor L.) following winter camelina (camelina sativa L.) as a dedicated oilseed biofuel feedstock was conducted. Combined analysis across year by location showed high camelina seed yield up to 1,531, 1,011 and 1,656 kg ha^-1 for Prosper, Carrington and Morris respectively. In relay-cropping systems (inter-cropping) highest biomass yield was 14.7, 7.2 Mg ha^-1 for camelina-sorghum relay treatment in Prosper and Carrington and 23.3 Mg ha^-1 for camelina-corn relay treatment in Morris. Energy efficiency was evaluated for double and relay cropping systems based on energy inputs and outputs. In Prosper energy efficiency was not significantly different for any of the cropping systems. However an energy efficiency value fluctuates from 1.6 to 21.6 GJ ha^-1 for Carrington and 5.6 to 34.7 GJ ha^-1 for Morris in 2013. Energy efficiency is higher for soybean, corn and sorghum in monoculture.  However camelina double and relay cropping systems showed significantly lower but positive energy efficiency. Especially camelina-sorghum relay treatment showed to be an alternative cropping system for biofuel and forage production in the Northern Plains of U.S.