Submitted to: Book Chapter in Text Forages
Publication Type: Book / Chapter
Publication Acceptance Date: February 16, 2012
Publication Date: July 31, 2013
Repository URL: http://farmwest.com/node/1303
Citation: Jokela, W.E., Russelle, M.P. 2013. Benefits of perennial forages in rotations. In: Bittman, S., Hunt, D., editors. Cool Forages, Advanced Management of Temperate Forages. Agassiz, BC: Pacific Field Corn Association. p. 84-87. Technical Abstract: Perennial forages are grown on over 23 million ha in the US and 8 million ha in Canada. Alfalfa is the most widely grown perennial forage species in both countries, but in the US the area of alfalfa has been declining steadily for the past 50 years, while the area of soybeans and, more recently, corn has been increasing. There is heightened public scrutiny of agriculture’s environmental ‘footprint’, so farmers, their advisors, and policy makers need to consider the total value of having perennial forages in their crop rotations. This chapter covers: a) the direct benefits of perennial forages used in rotation or as a cover crop; and b) the more far-reaching benefits of perennial forages in terms of improved soil and water quality. One of the reasons for the increase in corn area, and decrease in alfalfa area in the US, is that the amount of corn silage fed to U.S. dairy herds has risen significantly in the last 20 years. This has occurred for several reasons, including higher yield and dietary energy per hectare from corn silage. There are, however, a number of economic and environmental benefits from production of alfalfa and other perennial forages that sometimes are overlooked when comparing them to silage corn. One of the most important economic reasons to incorporate perennial forages into a rotation is the nitrogen (N) credit for the crop following the forage. Nitrogen released from decomposing forage tissue and from newly accumulated soil organic matter can supply most or the entire N requirement of a following corn crop, greatly reducing the need for purchased N fertilizer. In addition, first-year corn grown after alfalfa may have 10 to 15% higher yield potential due to factors other than N supply (“rotation effect”). A major concern with corn silage production is the increased risk of soil erosion and the associated phosphorus (P) loss, which can be greatly reduced, typically by 70 to 90%, by incorporating perennial forages into the rotation. Much of the benefit in controlling erosion is derived from the year-round vegetative cover perennial forages provide, but long-term studies also reported greater total organic C, higher total N, and greater overall soil quality in rotations with alfalfa than in grain systems. Another environmental concern is the leaching of nitrate into subsurface tile drains, which is much less from land in perennial forages compared to continuous corn or a corn-soybean rotation. And on top of all these benefits, nearly every economic analysis has concluded that alfalfa production is, on average, more profitable than corn. The fact that forages also can produce substantial direct and indirect economic returns should make the decision to include more forages in the rotation an easy one.