Question of the Week
Answer: Thank you for your recent request for information on organic alfalfa rotations.
(1) The Noble Foundation in Oklahoma does research and education on forages and livestock management, and makes the following recommendation on alfalfa rotations:
"...graze out alfalfa by September and prepare land for wheat or small grains pasture. Use the pasture through spring and then convert to millet or a sorghum-sudan forage for summer pasture or hay, removing the summer pasture by mid-August in order to plant an alfalfa variety in September. There will usually be enough residual nitrogen in the soil to make these two crops with no fertilizer needed. In essence, you would be managing an alfalfa stand for four to five years with one year of alternative forage production (with annuals) before returning to alfalfa again" (Aljoe, 2006).
The rotation basically looks like this:
Years 1 - 5 Alfalfa --> Year 5 fall planted small grain --> Year 6 spring pasture, then summer planted annual grass, then fall planted alfalfa.
(2) The University of Wisconsin has done some work on forage rotations on dairy farms and has found that "a three-year alfalfa stand - seeding year plus two - is more profitable than a five-year stand" (Pioneer). The rotation basically looks like this:
Year 1: Alfalfa --> Year 2 Alfalfa --> Year 3 Corn
Italian ryegrass can be seeded with the alfalfa the first year. Ryegrass germinates quickly and serves as an early weed control while the alfalfa is establishing itself. The ryegrass can be taken off as hay and make a high quality forage when harvested on or before the boot stage of development.
Practices to increase alfalfa yield and longevity
- Conduct a soil test. The following are some generalized ideal conditions to shoot for:
- Phosphorus - 15 ppm (parts per million)
- Calcium - above 300 ppm
- Ca:Mg ratio - 5:1 to 8:1
- pH - above 6.0
- Correct any deficiencies. For information on integrated methods of nutrient management, see the ATTRA publication: Nutrient Cycling in Pastures.
- Delay first cutting to later in the summer to allow for adequate root and crown growth .
- Fall harvest management - allow for at least 45 days from date of last cutting to first frost. This will ensure the alfalfa stand has enough time to repair root systems and develop enough leaf canopy to protect the plant crowns during the winter.
- Consider rotating the field out (through tillage and replanting) if:
- plant counts reveal less than 5 plants per square foot,
- plant counts reveal less than 40 alfalfa stems (on plants at least two feet tall) per square foot,
- plant counts reveal less than 2.5 plants per square foot for mixed alfalfa-grass stands.
- Rotate the alfalfa field to a small grain such as wheat or barley for at least one year to alleviate alfalfa autotoxicity issues.
The information that follows comes from some practical research done by Dennis Cash, Extension Forage Specialist with Montana State University, whom I have talked with numerous times on this topic. This reflects conditions in Montana, and the differences between Montana and your area will primarily involve dates of first frost, alfalfa fall dormancy, and types of annual crops used in rotations.
"Most research and producers agree that interseeding alfalfa into thin stands is rarely successful. Thickening an existing alfalfa stand is often unsuccessful because of soil conditions, age of stand, moisture and temperature conditions, disease, competition from weeds or older established plants and autotoxicity. When all of these conditions are added up, the deck is obviously stacked against a successful interseeding. When increased production is needed, one option might be to harrow the thin stand and drill an annual [small grain crop] with the intention of replacing the alfalfa stand the following year.
"Fall harvest management is [a large] determinant for alfalfa longevity. The current guideline [is] to optimize alfalfa winter survival... The actual dates vary...but correspond to a "rest" period of 30 to 45 days before the first frost UNTIL after several consecutive days of "killing" frosts. If fields must be cut or grazed in this period, do it on older fields closer to "retirement".
"The timing for alfalfa stand replacement depends on many factors. For irrigated alfalfa [or rainfed alfalfa in the eastern US], a stand of 4+ plants per square foot (or better, 60+ stems per square foot) is generally considered a viable economic stand. Each alfalfa producer should develop a "threshold" yield level for when to replace stands. The "threshold" will vary from operation to operation based on overall operation goals and requirements. Each operation should design a rotation plan for alternative annual forages to offset low production of new alfalfa seedings" (Dixon, et al, 2005).
Alfalfa Varieties and Hay Mixes
Choose varieties with relatively high fall dormancy ratings, but make sure you do not get one that will easily winter kill in your area. The more fall-dormant a variety is, (lower the number) the faster it will go dormant in the fall, and the better it will survive the winter. However, low-dormancy rated varieties will often come back better in the spring. Varieties with higher fall-dormancies typically produce more cuttings in a growing season and go dormant later, but might winter-kill and have more trouble coming out of dormancy. Talk to your local Extension agent to see what dormancy most growers use in your area. Contact information is for local cooperative extension offices can be found at http://www.csrees.usda.gov/Extension/index.html.
Research has shown that grass-alfalfa mixes often compete against weeds better than a pure stand. Perennial grasses occupy different niches in the soil than do the alfalfa, and can therefore compete against annual weedy grasses and broadleaf plants. And as long as the stand consists of at least 30% alfalfa, nitrogen fertilization for the grasses becomes unnecessary. Some mixes that have been shown to compete well against weeds are alfalfa-brome-trefoil, timothy-alfalfa, and orchardgrass-alfalfa, with the first mix being the most resistant to weed infestation and the last being the least resistant to weeds (Guerena and Sullivan, 2003). Brome-alfalfa is another mixture that does well in most areas.
References and Resources
Aljoe, Hugh. 2006. Alfalfa Is 'Almost Permanent' Pasture. Ag News and Views, Pasture & Range: November. The Samuel Roberts Noble Foundation, Inc.
www.noble.org/Ag/Forage/AlmostPermanent/index.html Banks, Scott. 2003. Alfalfa Stand Assessment. Ontario Ministry of Agriculture, Food, and Rural Affairs.
Dixon, Paul, Dennis Cash, Janna Kincheloe and J.P. Tanner. 2005. Establishing a Successful Alfalfa Crop. Bozeman: Montana State University Extension.
Guerena, M. and P. Sullivan. 2003. Organic Alfalfa Production. Butte, MT: National Center for Appropriate Technology.
http://attra.ncat.org/attra-pub/PDF/alfalfa.pdf Pioneer. Shorter--rotation alfalfa: Beating the high cost of nitrogen. PGP magazine/Forage.
Reinhart, R. (editor). 1990. Alfalfa Management/ Diagnostic Guide. Pioneer Hi-Bred International, Inc.
Sheaffer, Craig C., Donald K. Barnes, and Gary H. Heichel. 1989. "Annual" Alfalfa in Crop Rotations. Minnesota Agricultural Experiment Station, University of Minnesota.
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