Location: Plant Science Research
Title: Alfalfa: A Companion Crop with Corn Author
|Jung, Hans Joachim|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 18, 2010
Publication Date: June 29, 2010
Citation: Jung, H.G. 2010. Alfalfa: A Companion Crop with Corn [abstract]. Proceedings of the Alfalfa/Corn Rotations for Sustainable Cellulosic Biofuels Production, June 29-30, 2010, Johnston, Iowa. Available: http://www.alfalfa.org/2010WS/Jung.pdf. Technical Abstract: Corn grain-based ethanol is the major form of biofuel production in the USA. Corn is an attractive biofuel crop because it is easy to manage, process, and ship; is high yielding; and has significant industry support and research. However, there are concerns about growing corn in rotation with soybean or as a continuous corn crop for ethanol, including high energy inputs, high soil erosion potential, and high nutrient inputs and loss to the environment. Concerns have also been raised about diversion of grain from food and feed uses to bioenergy production, and land use shifts from set aside programs like CRP to corn production in order to meet growing demand for corn. Incorporating alfalfa into rotation with corn offers an opportunity to maintain biofuel production and alleviate the negative impacts related to continuous corn production. At the same time, this crop rotation would fulfill the food and feed needs for starch and protein traditionally provided by the corn/soybean production system of the American Midwest. Alfalfa is a perennial legume crop that is adapted and widely grown throughout the Corn Belt. Alfalfa does not require nitrogen fertilizer, an increasingly expensive production input for corn and other non-legumes, because alfalfa captures nitrogen from the air. It also scavenges excess nitrogen fertilizer left over from other crops, thereby protecting surface and ground water quality. When an alfalfa field is plowed down, alfalfa residues provide all of the nitrogen needed by the following year's corn crop and one-half the nitrogen needed in the second year of corn production, cutting corn nitrogen fertilizer use by 75% over 2 years. Corn grain yield is often boosted by 5 to 15% when corn follows alfalfa compared to corn following soybeans. If alfalfa were to partially replace soybeans in Midwest corn/soybean rotations, then nitrogen fertilizer use would decline and corn yields would rise; helping to meet the increasing demand for corn grain and reducing greenhouse gas emissions from natural gas use in fertilizer production. Alfalfa leaves are high in protein concentration. These leaves can be easily separated from the stems of dry alfalfa hay or stripped from standing alfalfa in the field. Alfalfa leaves yield at least as much total protein per acre as soybean. Alfalfa leaf protein is an excellent substitute for soybean meal protein in beef and dairy cattle diets. Thus, replacing soybeans with alfalfa in corn rotations would maintain feed protein production. When bioenergy production from cellulosic biomass becomes a reality, corn stover use will make corn an even more attractive crop because most production costs have already been charged to the grain, making the stover a very low cost additional product. Soybean provides very little harvestable stover and is not expected to contribute to cellulosic bioenergy. In contrast, alfalfa stem yield per acre is virtually equal to corn stover yield. Relatively little corn stover can be removed from the land without reducing soil carbon storage. In contrast, the large root system of alfalfa adds to soil carbon sequestration even when all above-ground biomass is regularly harvested. Soil carbon accumulation during the alfalfa phase of an alfalfa/corn rotation might replace or even exceed the soil carbon losses normally associated with corn stover removal, allowing sustainable and perhaps more removal of corn stover for bioenergy. The tremendous production capacity of the Corn Belt must be harnessed if we are to meet our national goals for bioenergy production, but we must not compromise traditional food and feed supplies. Other candidate bioenergy crops such as switchgrass, Miscanthus, and hybrid poplar require nitrogen fertilizer additions and do not provide protein products to replace soybean. Also, these other bioenergy crops do not have an established production infrastructure, as already exists for alfalfa. And while these other bioenergy crops effectively control soil erosion and sequester carbon, they must remain in place for many years, thereby displacing corn grain production for long periods. In contrast, alfalfa can be rotated with corn on a much shorter timeframe, 2 or 3 years of alfalfa followed by a similar period of corn production, essentially replicating the annual corn/soybean rotation. Such an alfalfa/corn system would reap most of the erosion control and soil carbon sequestration benefits of other bioenergy crops while maintaining or even increasing corn production. Although alfalfa is not adapted to all regions, it offers a unique set of advantages for enhancing the production of food, feed, and bioenergy in the Corn Belt by contributing to a more sustainable corn production system.