Maize (Zea mays L.) silage is the preferred feedstock choice for biogas production. However, other feedstocks or mixed feedstocks might have lower environmental impact than silage maize. The objectives of this study included: 1) to determine if forage sorghum [Sorghum bicolor (L.) Moench] and forage sorghum-maize intercropping can be a viable option to replace maize in forage and biogas production, and 2) to assess the environmental impact of systems involving maize and forage sorghum intercropping and comparing the impact of those, with conventional monocrop rotations. Replicated experiments were conducted in Carrington, Fargo, and Prosper, ND, in 2013 and in Fargo, ND in 2014. Maize for silage and grain and two forage sorghum cultivars (Brown Mid Rib (BMR) and non-BMR) were grown in monoculture and in intercropping. Treatments were a total of twelve; four monocultures, four inter-row intercropped maize-sorghum, and four within-row intercropped maize-sorghum. Results across environments indicated non-BMR forage sorghum monocultures produced similar or higher biomass yield compared with maize monocultures and maize-forage sorghum mixed cultures (inter-row and within-row). Biogas yield and forage quality produced by forage sorghum monocultures, and mixtures containing forage sorghum were similar to that of maize. Thus, forage sorghum can replace, at least in part, silage maize as feedstock for feed or biogas. Forage sorghum and forage sorghum-maize intercropping had lower environmental impact compared with maize in all categories evaluated. In conclusion, intercropping of forage sorghum with maize is a promising alternative to maize silage for forage or as feedstock for biogas production.

玉米（Zea mays L.）青贮饲料是沼气生产的首选原料。但是，其他原料或混合原料对环境的影响可能比青贮玉米低。这项研究的目标包括：1）确定是否饲喂高粱[双色高粱[L.] Moench]和饲草高粱-玉米间作可以替代牧草和沼气生产中的玉米，并且2）评估涉及玉米和饲草高粱间作的系统对环境的影响，并比较它们的影响，传统的单作轮作。2013年在北卡罗来纳州的卡灵顿和北卡罗来纳州的Prosper进行了重复试验，2014年在北卡罗来纳州的法戈进行了重复试验。玉米用于青贮和谷物，两个饲用高粱品种（棕中肋骨（BMR）和非BMR）在单一栽培中生长。间作。总共治疗十二次。四种单作，四种行间玉米/高粱和四种行间玉米/高粱。整个环境的结果表明，与玉米单一培养物和玉米-饲草高粱混合培养物（行间和行内）相比，非BMR饲用高粱单一培养物产生相似或更高的生物量产量。饲草高粱单一培养产生的沼气产量和饲草质量以及含有饲草高粱的混合物与玉米相似。因此，饲草高粱可以至少部分替代青贮玉米，作为饲料或沼气的原料。在所有评估类别中，饲用高粱和饲用高粱-玉米间作与玉米相比对环境的影响较小。总之，高粱与玉米间作是玉米青贮饲料或沼气生产原料的有前途的替代品。饲草高粱单一培养产生的沼气产量和饲草质量以及含有饲草高粱的混合物与玉米相似。因此，饲草高粱可以至少部分替代青贮玉米，作为饲料或沼气的原料。在所有评估的类别中，饲用高粱和饲用高粱-玉米间作与玉米相比对环境的影响较小。总之，高粱与玉米间作是玉米青贮饲料或沼气生产原料的有前途的替代品。饲草高粱单一培养产生的沼气产量和饲草质量以及含有饲草高粱的混合物与玉米相似。因此，饲草高粱可以至少部分替代青贮玉米，作为饲料或沼气的原料。在所有评估的类别中，饲用高粱和饲用高粱-玉米间作与玉米相比对环境的影响较小。总之，高粱与玉米间作是玉米青贮饲料或沼气生产原料的有前途的替代品。