Optimizing potassium applications and harvest strategies to boost productivity of depleting alfalfa stands

Rejuvenating thinning alfalfa ( Medicago sativa L.) stands with additional forage species have been ineffective in boosting productivity. Research is needed to identify practical solutions to extend the life of declining alfalfa and increase forage production. A 2‐year field study at the University of Wyoming James C. Hageman Sustainable Agriculture Research and Extension Center in Lingle, WY, investigated the interaction effect of K and harvest time on thin alfalfa stands. Treatments were (a) six K rates (0, 56, 112, 168, 224, and 280 kg K 2 O ha −1 year −1 ) applied to a ∼10‐year‐old alfalfa in the fall of 2019 and after the final harvest in the fall of 2020, and (b) two harvest times (early harvest, late bud to early [10%] bloom; late harvest, 7–10 days after early harvest), arranged in a 6 × 2 factorial under random complete blocks with four replications. Results showed a higher yield response to K at 224 kg K 2 O ha −1 year −1 and early harvest, and at 168 kg K 2 O ha −1 year −1 and late harvest particularly in soils with high soil test K levels (>300 mg kg −1 ). Harvest timing influenced alfalfa's K needs, with quadratic responses of forage accumulation to K rate observed at early ( p