Alfalfa FAQs

  • Which alfalfa variety should I plant?

    Plant a nondormant variety with a dormancy class of 8, 9, or 10 for the low elevation deserts. Choose a variety with appropriate pest resistance characteristics. Test new varieties in strips or small areas on your farm. Do not plant more than 25% of your acreage to a new variety. Use certified seed. Obtain "Nondormant Alfalfa Varieties for Arizona, 2001" from your local Cooperative Extension office for pest resistance characteristics and yield trial results.

  • What is the optimum seeding rate for alfalfa?

    20 pounds of seed per acre.

  • What is the optimum planting date for alfalfa?

    October (<3000 ft), September (3000 to 6000 ft), August (>6000 ft)

  • Can alfalfa be planted in the spring?

    Alfalfa can be planted in the spring, but forage yield is less over the life of the stand compared to late summer and fall plantings.

  • How much of a delay is required in planting alfalfa after alfalfa to avoid autotoxicity?

    2 to 4 weeks.

  • Should nitrogen fertilizer be applied to alfalfa?

    A well-nodulated alfalfa crop generally does not respond to alfalfa fertilizer. However, nitrogen as a starter fertilizer near planting may be beneficial. In studies where alfalfa has responded to alfalfa fertilizer, the response has often occurred at the first few cuttings in the spring.

  • How much phosphorus fertilizer should be applied to alfalfa?

    The phosphorus fertilizer rate recommendation is based on soil testing. Soil test values of >15, 11-15, 6-10, and <6 ppm bicarbonate extractable P correspond to none, 50-150, 140-250, and 200-300 pounds P2O5 per acre, respectively, applied at planting for a 3-year crop.  For annual applications or multiple applications per year, the total annual application should be a third of the above fertilizer application rates.  Annual or multiple applications per year may be necessary to maintain the soil test level in a desirable range for soils with a high phosphorus fixing capacity.

  • Can phosphorus fertilizer be topdressed as a granule to an established stand?

    Yes. Physical incorporation of phosphorus fertilizer is not necessary.

  • Which is a more effective fertilizer for alfalfa, liquid 10-34-0 or granular 11-52-0?

    Both are equally effective.

  • Does liquid 10-34-0 fertilizer move deeper in the soil than granular 11-52-0?

    No. Both remain primarily in the top foot of soil.

  • When is the best time to apply phosphorus fertilizer?

    October, or whenever phosphorus is needed as indicated by soil or plant testing.

  • Should I apply potassium fertilizer to my alfalfa?

    A response to potassium fertilizer for alfalfa grown on desert soils is rare, but is most likely to occur on very sandy soils.

  • Does alfalfa grown in Arizona respond to micronutrients?

    I am not aware of any documented cases of Arizona alfalfa responding to application of micronutrients.

  • How much water does alfalfa use?

    The seasonal water use for the Phoenix area is about 74 inches.

  • Will summer irrigation termination hurt my alfalfa stand?

    Yes, it can, but it depends on summer rainfall, availability of deep soil moisture, soil type, temperature, and other factors. The moisture status of the crown and root provides an indication of moisture stress: > 60% (well-watered), 50 to 60% (water-stressed), 40 to 50% (severe water-stress), <40% (lethal water stress).