A Comparison of Annual and Perennial Biomass Cropping Systems for Fuel and Feed.

A suite of biofuel feedstocks will be developed for meeting the emerging biomass-based energy economy.  The right choice for a given location will be dependent on many factors including local markets, growing climate, and available land resources.  This study was conducted to compare the productivity of annual and perennial bioenergy feedstock species on a Marshall Silt Loam (fine-silty, mixed, superactive, mesic Typic Hapludoll) in Central Missouri.  Annual cropping systems included two varieties of high biomass sorghum (HBS) and ‘M 81E’ sweet sorghum (SS) (Sorghum bicolor  Moench.) sown at 197,000 (HBS) and 148,000 (SS) PLS per ha^-1.  Perennial cropping systems included ‘Alamo’ and ‘Cave in Rock’ (CIR) switchgrass (Panicum virgatum L.) sown at 8.9 kg PLS ha^-1 and eastern cottonwood ‘ST-66’ (Populus deltoides Bartram ex Marsh.) planted at 14,345 stems ha^-1 in a double-row configuration. The effect of crop species on biomass production was evaluated in the first two growing seasons after establishment.  After two growing seasons, cumulative dry matter yield of the annual crops (‘ES5200’ and ‘ES5201’ HBS, and M 81E SS) produced 45.3, 33.7, and 34.2 Mg DM ha^-1, respectively over the two growing seasons.  Yields were similar between the sorghums and were greater than that of ST-66 cottonwood, and Alamo and CIR switchgrass which yielded 6.37, 2.17, and 2.09 Mg DM ha^-1, respectively.  Yields of the perennial crops were similar to each other. Low dry matter yields of ST-66 are attributed to tree mortality in the establishment year which averaged approximately 20%.  Low switchgrass yields were attributed to the multiple years of the establishment phase of this species which results in maximum yields 3-4 years following planting.  Results indicate that producers should weigh the benefits of receiving yields of annual crops yearly compared to the delayed maximum yields of perennial crops.