Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/24/2000
Publication Date: N/A
Citation: Interpretive Summary: Biomass fuels are being explored for their potential to replace or supplement nuclear and fossil fuels. Alfalfa is currently being investigated as a source of biomass for producing electricity. For this biomass project the leaves are used as a high quality animal feed while the stems are harvested and used to generate electrical energy. We investigated dthe effects of plant age and cutting frequency on leaf and stem yield and value to provide information for economic decisions about alfalfa biomass production systems using currently available alfalfa varieties. Results showed that producers should cut alfalfa more frequently at an early plant age (early flower) when livestock feed prices are high to maximize the economic return from the leaf meal product. For the best economic return when energy prices are high, we advise that producers cut less frequently at a later plant age (late flower) to produce more stem material to sell to othe power plant. This information will be used by producers to make management decisions on whether their alfalfa should be used for energy or feed markets resulting in maximum income from a biomass-fuel production system.
Technical Abstract: Biomass fuels are being investigated for their potential to replace or supplement nuclear and fossil fuels. Research has focused primarily on switchgrass (Panicum virgatum L.) and hybrid poplar (Populus sp.), but alfalfa has recently been considered as an alternative that may be easier for producers to fit into their farm operations. Alfalfa has the potential to produce high quality animal feed from the leaves as well as electricity from the stems. Our objective was to determine the effects of harvest regime on leaf, stem, and total herbage yield and quality of alfalfa to provide the biological basis for economic decisions about alfalfa biomass production in Minnesota. We grew six alfalfa entries at three locations and applied three harvest regimes involving three harvests per year at bud stage or early flower, or two harvests per year at late flower. Total leaf yields were greatest from the early flower harvests, and total stem yields were greatest from the late flower harvests. Bud stage herbage had the highest total herbage, leaf, and stem quality and highest leaf concentration, followed by early flower and then late flower harvest regimes. Herbage yield was highest and forage quality lowest at the first harvest of the season from all harvest regimes. Alfalfa entries differed in herbage quality and leaf concentration but did not consistently differ in total herbage or stem yield. Harvest regime effects were consistent across locations and alfalfa entries. Harvest regime had no effect on final stands. For an alfalfa biomass energy system, producers should choose an early flower harvest regime when livestock feed prices are high and a late flower harvest regime to produce stem material when energy prices are high.