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A hard winter resulted in some thin alfalfa stands across many areas this spring. Scouting fields to observe plant health, fertility needs, and pest problems will be important to maintain good alfalfa stands. Proper harvest management of alfalfa can have a huge influence on yield, quality, and stand persistence.
Figure 1. Phosphorus (P) deficiency in alfalfa can result in thin, weak stands with stunted plants and dark color. Potassium (K) deficiency in alfalfa can result in browning and spotting on leaf margins and tips.
If fields were slower to green-up this spring, it may be a signal to evaluate the alfalfa stand for winter injury and plant health. Management is the key to successful alfalfa production, and supplying the correct amount of nutrients is one important management factor. Nutrient deficiencies can reduce alfalfa yields and shorten stand life.1 Soil testing should be done to accurately estimate nutrient requirements, especially phosphorous (P) and potassium (K). Alfalfa can remove large amounts of K from soil, and annual applications will generally be necessary to maintain recommended soil test levels. Broadcast applications of P should also be made in the fall or early spring according to soil testing. Visual plant symptoms may indicate nutrient deficiencies; however, by that time, significant yield losses have already occurred (Figure 1). Symptoms may also be caused by other factors such as environmental conditions, diseases, restricted root growth, or other problems not related to nutrient deficiencies. A plant tissue analysis may be necessary to confirm symptoms are nutrient related.
Figure 2. Examples of cutting schedules for different management goals. Adapted from Alfalfa Management Guide, American Society of Agronomy.3
Harvest management can have a tremendous influence on alfalfa yield, quality, and stand persistence.2 Harvest management involves planning for the number of cuts per season, date of cut, stage of maturity, interval between cuts, and cutting height (Figure 2). Obtaining high yields requires cutting at late-maturity stages, whereas cutting early maximizes quality; however, focusing on just one or the other can reduce stand persistence and shorten the life of the stand. Cutting management decisions can be complicated by the possibility of winter injury to frequently-cut alfalfa stands with depleted carbohydrate reserves. Growers may need to consider allowing alfalfa plants to mature longer before cutting if stands have symptoms of winter injury.
The goal of growing alfalfa is to optimize profitability by maximizing both yield and quality without jeopardizing stand life.2 In order to preserve the stand and permit it to reach its potential, some degree of balance is needed between obtaining yield and quality when making harvest management decisions. Scheduling harvest of the first two cuttings is critical to maximize yield of high quality alfalfa. Rapid changes in forage quality can occur during this time period and delayed cutting can reduce quality. For high yield and high quality, the first cutting should be taken at bud stage. The second cutting should be taken 28-33 days after the first cut, or at mid-bud stage, whichever is earlier. After that, a subsequent cutting should take place 38-55 days later or at 10-25% bloom. Letting the stand mature a bit longer before the third cutting can build up root reserves and boost stand persistence. The forage quality of alfalfa does not change as rapidly in later cuttings compared to earlier cuttings.3
In the fall, alfalfa stands need a break from harvest during the 6 to 8 weeks prior to the first killing frost. This rest period permits plants to build up adequate reserves of carbohydrates in the roots before winter begins. If plants are cut during this rest period, it may reduce the speed of regrowth and yield potential of the first cutting next season, along with thinning or killing the stand. Although some growers have success making a final cutting after the first hard freeze, it is not generally recommended. The decision to cut during the fall rest period is an individual one and should be made after careful consideration of the risk factors as compared with the need for additional forage.
Finally, the degree of pest problems can be influenced by alfalfa vigor and cutting frequency. Continuously cutting alfalfa at immature growth stages can alter the plant’s ability to withstand insects and diseases, and result in higher weed infestations.2
1 Koenig, R., Hurst, C., Barnhill, J., Kitchen, B., Winger, M., and Johnson, M. 1999. Fertilizer management for alfalfa. Utah State University Cooperative Extension. http://www.extension.usu.edu. 2 Orloff, S. and Putnam, D. 2004. Balancing yield, quality, and persistence. Proceedings, National Alfalfa Symposium. University of California - Davis Cooperative Extension. http://alfalfa.ucdavis.edu. 3 Undersander, D., Cosgrove, D., Cullen, E., Grau, C., Rice, M., Renz, M., Sheaffer, C., Shewmaker, G., and Sulc, M. 2011. Alfalfa Management Guide. American Society of Agronomy. http://www.agronomy.org. Web sites verified 6/9/16. 160608214618