Alfalfa Fertility

 Knowledge Nuggets | Fact Sheets | Research Papers
Knowledge Nuggets
  • Soil test to determine availability of soil nutrients and nutrients that are inadequate.
  • Water and nutrients are the two most important factors controlling the growth of an alfalfa forage crop.
  • There are 20 elements that are needed for plant growth and a deficiency in any of these nutrients limits productivity. There are eight common deficiencies. The major nutrients include: nitrogen (N), phosphorous (P, in the form of phosphate P2O5) and potassium (K, in the form of potash K2O). The secondary nutrients include: sulphur (S), magnesium (Mg) and calcium (Ca). The minor nutrients include: zinc (Zn) and boron (B).
  • Fertilizer recommendations should be based on the averages from field and laboratory tests. Yield goals should be considered and be based on historical rainfall. Adjusting fertilizer rates based on realistic yield goals is essential to maintain environmental quality, to optimize economic returns and maintain stand longevity.
  • In general, once an alfalfa stand has been established, you will not need to apply nitrogen fertilizer because of its symbiotic relationship with nitrogen-fixing Rhizobium bacteria. Nitrogen application will not increase yields, quality or stand vigour and may reduce yield and quality due to increased growth of grass species and weeds.
  • Alfalfa needs a good supply of phosphorous for successful establishment, for good root development and health. Potash is needed to maintain yields, reduce disease incidence, improve winter hardiness and increase stand survival.
  • Phosphate and potash are immobile in the soil and should be incorporated into the soil rather than top-dressed. A large single application of phosphate (100-200 lb/a) prior to establishment may be beneficial in low P soils.
  • Deficiencies in S can occur when alfalfa is grown on light sandy soils or on low organic matter soils. Sulphate-S is readily available to the crop, whereas, elemental S has to be converted to sulphate before it can be used.
  • For stands that contain more than 60% alfalfa, the following are general annual fertilizer recommendations: 0-10 lb N/a, 0-60 lb/a P2O5 and 0-30 lb/a S.
  • The best time to apply fertilizer is in the early spring when the plants begin to grow, taking care to apply the proper type of fertilizer.
Fact Sheets

Alfalfa Fertilization - available in PDF format only

Fertilizing Alfalfa Forage - available in PDF format only

Fertilizer Requirements of Irrigated Alfalfa

Impact of Alfalfa and Fertilizer on Pasture: Economics - available in PDF format only

Is Swine Manure Injection into Alfalfa Stands a Good Idea? - available in PDF format only

Legume Innoculation Cuts Fertilizer Need

Managing Manure on Alfalfa Hay

Northern Idaho Fertilizer Guide: Alfalfa

Soil and Nutrient Management of Alfalfa

Management of Grass-Alfalfa or Alfalfa-Southeast Saskatchewan - Available in PDF format only

Research Papers

Effect of fertilizer on seed yield of alfalfa under irrigation in Saskatchewan - available in PDF format only

Let us know of more good research papers for this topic.
  For more information about the content of this document, contact Grant Lastiwka.
This document is maintained by Janet Fletcher.
This information published to the web on October 24, 2003.
Last Reviewed/Revised on February 21, 2017.

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