Tips for fall planting of alfalfa

Stacy Campbell
News Column Cottonwood Extension District, Hays

September 9, 2021 Kansas has 568,324 acres of alfalfa, which is a very important leguminous crop for the dairy and livestock industry in Kansas. Alfalfa hayfields help to supply forage that is highly digestible and high in protein. Late summer and early fall are often the best times to plant alfalfa in Kansas due to less weed pressure than spring planting.  

Available moisture at planting is crucial for alfalfa establishment, but too much moisture can increase seedling disease incidence and reduce alfalfa nodulation and nitrogen fixation. 

If soil moisture is available, growers in northwest Kansas can plant as early as August 10. Optimum sowing date occurs later as we move towards southeast Kansas, where growers can plant until mid- to late-September. In other parts of Kansas, the optimal planting time is late August or early September. Producers just need to plant early enough to have three to five trifoliate leaves before the first frost. 

Alfalfa is a four to five-year, or longer, investment, and therefore it is crucial to ensure proper establishment. Some producers shy away from alfalfa because of its high establishment cost and risk of stand failure. In the long run, however, it’s relatively inexpensive if amortized over the life of the crop. 

If managed properly and given favorable weather conditions, dryland alfalfa can produce 3 to 6 dry matter tons of forage per acre per year. Irrigated fields can produce 6 to 8 dry matter tons per acre per year or more. 

When sowing alfalfa, producers should keep the following in mind: 

Soil test and correct soil acidity. Alfalfa grows best in well-drained soils with a pH of 6.5 to 7.5 and does not tolerate low soil pH. If the soil is acidic, add lime to raise soil pH to 6.8 before planting. Ensuring appropriate soil pH levels before planting is essential, especially as lime is relatively immobile in the soil profile and the field will not be worked for the next 3-5 years. Remember, after spread, lime takes a few weeks in the soils to react and increase the pH. 

Soil test and meet fertilization needs. Apply the needed phosphorus (P) and potassium (K) amounts according to soil test recommendations. Phosphorus fertilizer will be required if soil test P levels are below 25 ppm, and potassium fertilizer will be required if soil K levels are below 120 ppm. Even soils that test higher than these thresholds may need additional fertilizer. Small amounts of nitrogen fertilizer (15 to 20 lb/acre) as a starter at planting are beneficial for alfalfa establishment. In some fields, sulfur can also bring some yield benefits. 

Plant certified, inoculated seed. Ensuring the correct Rhizobium inoculation is crucial for alfalfa seedlings to fix available soil nitrogen to meet the needs of growing alfalfa for optimum production. 

Plant in firm, moist soil. A firm seedbed ensures good seed-soil contact; therefore, use a press wheel with the drill to firm the soil over the planted seed. No-till planting in small-grains stubble will usually provide a good seedbed. 

Don’t plant too deeply. Plant one-fourth to one-half inch deep on medium- and fine-textured soils and three-fourths inch deep on sandy soils. Don’t plant deeper than 10 times the seed diameter. 

Use the right seeding rate. Plant 8 to12 pounds of seed per acre on dryland in western Kansas, 12 to15 pounds per acre on irrigated medium- to fine-textured soils, 15 to 20 pounds per acre on irrigated sandy soils, and 12 to 15 pounds per acre on dryland in central and eastern Kansas. 

Check for herbicide carryover that could damage the new alfalfa crop – especially when planting alfalfa no-till into corn or grain sorghum stubble. In areas where row crops were drought-stressed and removed for silage, that sets up a great seedbed for alfalfa but may still bring a risk of herbicide damage. 

Choose pest-resistant varieties. Resistance to phytophthora root rot, bacterial wilt, fusarium wilt, verticillium wilt, anthracnose, the pea aphid, and the spotted alfalfa aphid is essential. Some varieties are resistant to even more diseases and insects, which could contribute to reducing costs. 

Purchase alfalfa varieties with a fall dormancy rating ranging from 4 - 6 for Kansas. Fall dormancy relates to how soon an alfalfa variety will stop growing in the fall and how early it will begin growing in the spring or late winter. Simply put, it would be better not buy a variety with fall dormancy of 9-10, which can be more suitable for California and regions where alfalfa can keep growing year-round under irrigation. 

More information about growing alfalfa in Kansas can be found in the Alfalfa Production Handbook. That information also is available on the web at: www.ksre.ksu.edu/bookstore/pubs/c683.pdf 

Also see Alfalfa Growth and Development, available on the web at: https://www.bookstore.ksre.ksu.edu/pubs/MF3348.pdf 

 Stacy Campbell is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at scampbel@ksu.edu or calling 785-628-9430.