Alfalfa is, without a doubt, the most complex forage. Because of its many uses, importance in the dairy, beef and equine industries, and use in many different climatic regions, there has been a significant amount of research done on alfalfa. As a result, there are literally hundreds, if not thousands, of varieties. CHS Seed Resources secured a line-up of high-performing varieties that are priced affordably. So how do you decide what alfalfa product is best for your situation?
Fall Dormancy (FD): This number determines how early in the fall/winter a variety goes dormant and how late in the spring it comes out of dormancy. The FD rating is separate from the winter hardiness rating, although the two are partially related. The FD rating should be the first characteristic you consider, as it determines your management/harvest schedule. In general, the FD number allows a grower to get that many harvests, plus one. So if a variety is a FD 3, a grower can expect to get 3 or 4 timely cuts at 10%-25% bloom (peak harvest time with high yield and good quality). Generally, select a FD based on the number of times you can harvest the field. If you select a FD 4, but only cut two or three times per year, your harvests may yield well but be over-mature and poorer quality (very stemmy).
For the far northern U.S., a FD 4 is usually the highest FD that is recommended. Anything higher and the plant tries to grow longer into the fall and risks severe freezes before it goes dormant, and tries to come out of dormancy in the spring before temperatures are really warm enough. Dormancy is controlled by daylight length first and temperature second.
In the central U.S, a FD 5 can be grown, as long as it has a strong winterhardiness rating.
In the Plains, south of I-40, a FD 6 is ideal (although FD 4 and 5 varieties have shown better drought tolerance in many cases, probably because they are not trying to grow as rapidly, and don’t require as much water at one time).
South of the Red River in the southern Plains and the Southwest, a FD 7 is very productive and in California and the Southwest, a FD 8 or 9 (non-dormant) is used.
Winter Hardiness Rating (WH): For areas of the central and northern tier of the U.S., the winter hardiness rating is important. The scale runs from 1 to 5, with 1 being the most winter hardy. Many of the newer varieties on the market are very winter hardy. For FD 5 or lower varieties, always select a variety with at WH around 2.5 or lower, although many varieties now have a rating of 2.1 or lower, which indicates exceptional winter hardiness.
Disease Resistance/Rating Index (DRI): The DRI is very important in the Midwest and East where humidity is high and disease pressure is intense, but other regions have numerous diseases that must be considered. The DRI is a scale that measures disease resistance to six common alfalfa diseases – anthracnose, aphanomyces (race 1), bacterial wilt, fusarium wilt, phytophthora root rot, and verticillium wilt. Each disease is given a rating of 1 to 5, with 5 being the best. So the best total score is 30 (six diseases with a high score of 5 for each). FD 5 and lower varieties are rated on all six diseases. For those varieties, select a variety that has a perfect or near perfect rating (29 or 30 out of 30). For FD 6 and higher varieties, identify the major diseases in your area and compare that to the resistance of the varieties you’re considering.
Leaf Hopper Tolerance: In the eastern Great Plains, Mississippi River Valley and East, potato leaf hoppers can severely damage a crop. Leaf hoppers look like miniature grasshoppers that aren’t much larger than an alfalfa seed. The stick their beak in the stem to suck our moisture and nutrients. The plant then forms scar tissue in that area, blocking the flow of moisture and nutrients to that part of the plant. As a result that part of the plant turns yellow and dies. If you see large patches of yellow in your alfalfa crop, you very well could have a leaf hopper infestation, and those little pests can decrease the yield by 50% or more and even kill young alfalfa stands. Spraying can be effective. But for those that don’t want to spray or have mixed alfalfa/grass stands, a great option is a leaf hopper tolerant variety, which has longer hairs along the stem that prevent the leaf hopper from reaching the stem.
Number of Harvests: Alfalfa, in general, regardless of variety, has about 16 high-end cuts in its lifespan. After 16 cuts, the plant is starting the downhill slide of its life. It may continue to grow for years, but its production significantly declines. If you carefully measure your yields, you'll often discover that after 16 cuts, yield has dropped to a point where it is economically advantageous to terminate the field and establish a new field.
Predicting Yields: For peak yield, a stand should have about 55 stems per square foot. For every 10 stems less than 55, the stand yields about 1 ton less dry matter per acre per year.
Doctor Checkup: To measure the health of your stand, dig up roots and cut the crown and taproot in half. If the inside of the crown and taproot is bright white, the plant is healthy and likely has at least two years of good production left. If some black rot is starting to show in the center of the crown/taproot, the field should be taken out of production after that growing season. If the crown/taproot has extensive black rot in the center, the field is not economical and should be converted to another profitable forage immediately.
Micro Needs: Micronutrient and growth regulator applications can greatly increase yield. Tissue sampling is the best way to determine what micronutrients are needed.
Weed Control: Roundup Ready alfalfa can offer advantages if you have tough weed/grass problems. Conventional alfalfa is tolerant to the traditional grass and broadleaf herbicides labeled for alfalfa, but weed and grass control can occasionally be difficult. Roundup Ready alfalfa should be sprayed with glyphosate within 30 days of germination. The glyphosate application does two things. First, if kills the first weeds and grasses coming up in the stand. Early weed and grass pressure can reduce establishment rates, unknowingly reducing your yields for the life of that stand. Second, the glyphosate application kills up to 5% of the alfalfa seedlings. Why? Due to the genetic complexity of alfalfa, a small percentage of the seeds in each bag of RR alfalfa do not carry the RR trait. Alfalfa naturally thins itself in the first year, even in a field free of weeds of grasses, until it reaches a certain population. By immediately killing off the non-tolerant plants, it allows the tolerant plants to have a better chance of maturing.
Seeding Rate: 15-20 lbs/acre. Research has proven that there is no advantage in pure alfalfa stands for seeding rates exceeding 12-14 lbs/acre. However, planting equipment is often not precise enough in lbs/acre in real-world environments to ensure a desired stand at those lower seeding rates. Therefore, bumping up the seeding rate provides a better opportunity for a healthy stand.
Soil Type: Well-drained soil with depth.
Soil pH: 6.5 to 7.0 (pH must be, at a minimum, in the low 6-range at planting time or stand will not perform up to its potential).
Planting Times: In the North and Central U.S., plant in early spring or late summer. In the South and Southwest, plant in late summer.
Planting Depth: ¼ inch
Forage Quality: Excellent
Drought Tolerance: Excellent
Heat Tolerance: Excellent
Winter Hardiness: Varies
Longevity: Alfalfa, regardless of variety, generally has 16 quality harvests in its life before yields start to quickly decline.