Time of Seeding for New Alfalfa Establishment
Timing of seeding for new alfalfa establishment is critical to the success of the emerging crop and for the future success of the stand. Factors to be considered when planning are temperature, rainfall pattern, weed pressure, and time of year when environmental conditions are optimum for the seedling germination and crop emergence. Unfortunately, no single time period will fulfill all these conditions satisfactorily. Benefits and drawbacks of each time period need to be considered by the producer.
Alfalfa is extremely cold tolerant at emergence and this can give a false sense of security, but as the plant develops to two trifoliate leaves, frost sensitivity becomes greater and it may be killed by exposure to 26 degrees F for as little as 4 hours until it reaches the three trifoliate leaf stage.
In the Northern Great Plains, a spring planting for alfalfa establishment is more likely to be successful than a late summer planting. This is because moisture is adequate in the spring and cool but not freezing conditions can support good germination and growth (germination begins at 40F degrees soil temperature). Fields may be difficult to enter into due to wet soils, but alfalfa may be planted as soon as danger of spring frost has passed.
Summer weed competition can be alleviated by planting with an annual companion crop such as oats.
Alfalfa, during growth, is not tolerant of a high water table that could drown it out. Equally as important is that the site receive enough water for successful growth. Sandy to clay loamy soils are best. Sand dominated or clay dominated soils will pose problems to water management.
Planting during the summer is not recommended due to the potential for increase of weeds.
LATE SUMMER PLANTING
Planting in the first two weeks of August is a possibility IF soil moisture is sufficient. PLANTING AFTER AUGUST 15TH IS NOT RECOMMENDED DUE TO THE LIKELIHOOD OF FROST CONDITIONS THAT CAN DAMAGE EMERGENT YOUNG PLANTS.
Alfalfa requires a minimum of six weeks after germination, and before a killing frost to ensure survival. At least four trifoliate leaves and the formation of a crown are necessary for winter survival.
Advantages of a late summer planting are a decreased competition with weedy species and an increased yield the following year when compared with spring planting. However, late summer plantings come with higher risk due to unpredictable rainfall and early frost.
Authored by: Fara Brummer, Area Extension Specialist, Livestock Systems, Central Grasslands Research Extension Center
2014. Stage of Alfalfa for Winter Survival (M. Bohle, personal communication, August 14, 2014)
2011. Undersander, Dan et.al. Alfalfa Management Guide. American Society of Agronomy, Inc., Crop Science Society of America, Inc., and Soil Science Society of America, Inc.
1997. Benton et. al. Intermountain Alfalfa Management. University of California, Division of Agriculture and Natural Resources. Publication 3366