USDA-ARS and University of Minnesota researchers teamed up in an effort to assess the impact of potassium fertility on crown rot disease in alfalfa. Along with being alfalfa’s most common deficiency, lack of the nutrient is also one of the most recognizable. Lower leaflets develop yellow or white spots around margins, which then grow together and eventually cause total necrosis. Potassium deficiency can result in stand loss, winterkill, and extensive weed growth.

While potassium has been linked to disease resistance, there have been no direct indications that it alone is a solution. Two experiments were performed to measure potassium’s effect on crown rot disease and forage yield. The first experiment used five cultivars seeded at four diverse Minnesota locations. Potash (K₂O) was applied annually at 0, 125, or 350 pounds per acre, and plants were rated for the amount of crown rot after the third production year. Results across all cultivars and locations indicated a clear reduction in crown rot symptoms with potassium fertilization. There was also significantly greater number of plants that showed absolutely no symptoms of crown rot. Learn more about the second study by viewing the full article, here.