Response of alfalfa to fertilization with P and Mg in the greenhouse

Abstract

Alfalfa (Medicago sativa L.) needs a considerable amount of P and Mg for maximum growth and production. ‘Lew’ alfalfa was grown in a greenhouse‐pot trial in Mohave sandy loam soil with several rates of P and Mg applied singly and in combination. There was a positive response to P applied alone, but Mg applied alone reduced plant growth even though herbage‐Mg concentration was increased (from 0.22% to 0.40% with the highest rate of 400 kgMg/ha). However, fertilization with both Mg and P resulted in a significant yield response and a higher herbage‐P concentration than when only P was applied. Within the conditions of this experiment, a response to fertilization with Mg is likely to occur only when the level of the P in the plants is adequate.

Key words:

• Medicago sativa
• number of shoots
• herbage yield
• root yield
• total plant yield
• herbage elemental concentrations