Topics : Species and Forage Variety Trials : Species Fact Sheets : Alfalfa
Before Planting -Information on adjusting soil nutrient levels before seeding is available.
During Establishment - Have a soil test taken to determine lime and fertilizer needs for alfalfa establishment. Fields to be seeded to alfalfa should be limed to pH 6.5 to 7.0. Needed lime should be applied at least 6 months to a year before seeding to allow the lime time to react with the soil and minimize triazine herbicide carryover. For maximum production, seed only in soils that are already at a pH of 6.2. Generally, for soils below this pH, lime should be applied but seeding delayed. Starter fertilizer applications of up to 20-60-20 per acre are desirable at seeding time. Band placement is highly recommended. Plant nutrients recommended in excess of this amount should be incorporated into the seedbed before seeding. If soil test recommendations are followed at planting, additional applications of fertilizer in the fall of the seeding year are not necessary.
Additional and more detailed information on forage fertilization during establishment is also available.
Established Stands - High levels of phosphorus and potassium must be maintained in the soil for high crop yields and long-lived alfalfa stands. Determine lime and fertilizer needs by soil test. High alfalfa yields can reduce plant nutrient levels in soil rapidly. Thus, for top production and stand persistence, annual soil testing is recommended.
When a soil test indicates the need for fertilizer, topdress after first and/or last cutting. Split applications, one-half in fall and one-half after first cutting, may result in more efficient use of fertilizer, especially potash. Recent research suggests that, based on nutrient removal, a 0-1-4 ratio of N-P2O5-K20 is best when high yields are anticipated. If the soil test is 1 part per million (ppm) or less of boron (B), or plant tissue has 25 ppm or less B, then topdress with a fertilizer containing at least 2 pounds of B per acre.
At present, there is no evidence to indicate a general need for other fertilizer nutrients. Recent research does suggest that in certain isolated cases small responses from sulfur may be obtained.
Additional and more detailed information on fertilization of established forage stands is also available.