Growing Alfalfa for Seed
The cultivation of alfalfa for the production of seed is well suited to the dry Western climate because it allows good seed drying and harvesting conditions. Although the crop produces better in heavier soils, the sandier soils can also produce good seed yields if managed effectively. In the lower deserts, alfalfa seed production may be intentional or on fields already harvested once or twice for hay earlier in the season. When planning alfalfa seed production, the alfalfa should be planted in rows to facilitate harvest and threshing of the seed, whereas fields planted for hay production tend to have lower yields and make harvesting seed a little more difficult due to increased seed loss during harvest. Typically, for optimal seed production, a plant density of less than 100,000 plants is recommended, or a seeding rate of 0.9-1.3 lbs/acre.
It is important to make sure that weed control is effective during stand establishment to reduce seed contamination. To avoid mixtures of varieties, the grower should also ensure that the ground is not subject to volunteer alfalfa contamination. Row planting helps in the control of weeds and volunteers through cultivation approaches, and may also improve access to flowers by pollinators.
If the plants are being grown specifically for seed production, yield is usually enhanced if the plants are cut or clipped earlier in the season for hay production or by sheep grazing. If weed control is needed, the window after cutting or grazing may offer the most appropriate timing. As it is for hay production, alfalfa grown for seed should be maintained at the optimum nutritional level through the use of frequent soil and tissue analysis, allowing timely application of fertilizers and micronutrients.
Pollination can be achieved with either honey or leafcutter bees, with the latter being increasingly popular in the lower deserts. Honey bees do not find the alfalfa flowers as attractive as do the cutter bees, and they are far more particular about honey concentration, which can be significantly impacted by irrigation timing relative to blooming.
Pest control is always necessary in alfalfa since it is such an attractive crop for a range of pests such as mites, lygus, weevils and worms. If chemical control is necessary, every effort must be made to make applications well in advance of flowering and to use products that would facilitate the buildup of beneficials at the time of flowering. As flowering is initiated, the use of products that improve flower production, pod retention and seed fill can significantly increase seed yield. There is some suggestion that such approaches may also make the flowers more attractive to honey bees that do not normally find alfalfa an attractive crop. Often, a combination of honey bees with the more expensive, but more efficient, leafcutter bees is used to optimize seed production. Seed can be harvested by windrowing or the use of a desiccant followed by combining. With either method, no time should be lost once the crop is dry to avoid excessive loss from pod shatter.
Your Helena representative can provide a wide range of products to service your alfalfa needs from insect control to nutrition. For example, Liquid Chisel® can help remediate salty soils, and Retention®, through center pivot or other irrigation systems, can hold water more effectively in the upper soil profile. Megafol® can significantly improve the plants ability to withstand stress conditions such as extreme temperature or low humidity, while products such as eXploit® or Utilize® PK can be used to improve seed set, harvest yield and profitability. Contact your Helena representative for more information on these and other products.
- Dr. Ian Watkinson, Desert Product Manager, Western Division