Alfalfa
Alfalfa as a Biofuel Crop
Alfalfa (Medicago sativa L.) is the most important
high-quality forage crop because of its high protein, vitamins, energy,
and digestibility. Alfalfa can be used whenever herbivores need a high
quality diet for growth, stamina, strength, or production of meat,
milk, wool, and eggs. It is grown over a wide range of temperate
and subtropical environments. Alfalfa was first successfully grown in
the southwest U.S. during the mid 1850's and is now most
intensively grown in many states.
Alfalfa is used as a high-quality
component of forage mixtures and allows use of lower-quality forages in
rations. It is also important for soil enrichment, soil water holding
capacity improvement, mulch, and extraction of deep minerals and
nitrogen. It is even used directly by humans in nutritional tablets and
health food!
High-yielding alfalfa requires deep soils to store an abundant water
supply for season-long growth. High yield requires large quantities of
water (from rainfall, water table, or irrigation). Alfalfa requires
approximately 6 inches of water in the root zone for each ton of hay
produced per acre per year. In addition soils should have a pH
near neutral (6.6-7.5) and be fertile enough to supply large quantities
of nutrients.
Harvesting five tons of hay per acre removes approximately 50 pounds of phosphorus (P205), 100 pounds of calcium, and 220 pounds of potassium (K2O) from the soil. Eventually these nutrients must be replenished with fertilizer applications as indicated by a soil analysis.
All soil textures (sands, loams, and clays) can be used for alfalfa; however, soils should be well drained to avoid root and crown diseases and to allow oxygen flow to roots for nitrogen fixation by Rhizobium bacteria. Soils with pH near neutral favor nutrient availability and Rhizobium activity for good alfalfa production.
Reasons for promoting alfalfa as a biofuel crop include its high biomass production; the fact that it is a perennial; and can fix its own nitrogen when grown with the appropriate Rhizobium bacteria. It is generally thought that primarily alfalfa stems would be used for biofuel and leaf by-products would be used in the animal feed industry.
The main reasons cited against alfalfa becoming a biofuel crop is that it should be grown on soil of our best soils and varieties adapted to single harvests per year have not been developed for most of the country. Harvesting alfalfa four to six times per year and its high nutrient requirements drive up production costs and make it unlikely to become a prominent biofuel crop.
Web sites about alfalfa as a biofuel crop:
http://www.ars.usda.gov/SP2UserFiles/Place/36401000/AlfalfaforBiomass.pdf
