Potassium! Why It Matters to Alfalfa Persistence

By Christina Curell and Kim Cassida

Alfalfa is a mainstay in Michigan hay and haylage production but stand persistence is always a challenge under intensive harvest schedules. One reason for this is the high requirement of alfalfa for potassium. Potassium helps drive over 60 enzyme and hormone reactions, while supporting photosynthesis and protein production and helping plants tolerate stress. A ton of dry alfalfa hay contains about 48 pounds of potassium. Therefore, a modest alfalfa yield of 5 tons per acre removes 290 pounds of potash equivalent from the soil every year. Nearly half of alfalfa fields surveyed in Michigan were low or borderline for soil potassium. This matters because potassium is extremely important in supporting alfalfa tolerance to environmental stresses, especially winterkill, drought and diseases. Low availability of soil potassium is a common finding in alfalfa fields that are underperforming.