Comparative economic analysis of perennial, annual, and intercrops for biomass production

Herbaceous crops may be an important source of renewable energy. Production costs can be more competitive by increasing yields so that overhead costs are applied to more biomass. Most previous economic studies of energy crops have concentrated on the production of switchgrass (Panicum virgatum L.). This study analyzes the biomass yield and economic potential of several hig h-yielding annual and perennial crops on prime and marginal, sloping land. Crops evaluated were reed canarygrass (Phalaris arundinacea L.) harvested t wice per year; switchgrass and big bluestem (Andropogon gerardii Vitman var . gerardii); alfalfa (Medicago sativa L.); and sweet sorghum, forage sorghu m [both Sorghum bicolor (L.) Moench], and maize (Zea mays L.). The intercro pping of the two sorghum species into reed canarygrass and alfalfa was also analyzed. All crops but alfalfa were fertilized with 0, 70, 140, or 280 kg N ha(-1), with economic analysis performed assuming 140 ka N ha(-1). Sorgh ums were most productive, with more than 16 t of dry matter ha(-1). Switchg rass was the highest-yielding perennial crop, Costs per ton of biomass prod uced were lowest for sorghum, somewhat higher for switchgrass, higher still for big bluestem, and highest for alfalfa and reed canarygrass. Yields per ton for intercropped species were higher than for perennial species but lo wer than for monocrop sorghum. Costs per ton for intercropped species were less than for either alfalfa or reed canarygrass, but were higher than cost s per ton of monocrop sorghum. Although the sorghums had the highest yields , high potential for erosion on sloping soils may preclude their use on the se soils. (C) 2001 Elsevier Science Ltd. All rights reserved.