Influence of potassium fertilization on alfalfa leaf and stem yield, forage quality, nutrient removal, and plant health

Abstract Potassium (K) is an essential nutrient for plant growth. In K‐deficient soils, fertilization has been shown to increase herbage yield of alfalfa. The purpose of this study was to determine the effects of K fertilization on alfalfa leaf and stem yield, forage quality, nutrient removal, and plant health of a nonlodging experimental germplasm. Five alfalfa rotations had K fertilizer applied at three rates (0, 186, and 372 kg K ha−1) to soils already containing sufficient soil test K (223 mg kg−1). No overall yield differences were found related to K application rates, though K removal in total herbage increased by 30–58% with K fertilization, depending on alfalfa stand age. Leaf:stem ratios were not impacted by K fertilization. The concentrations of B, Ca, and Na decreased with K fertilization, while K concentrations increased, which may have resulted in B deficiencies. Leaf in vitro digestibility decreased significantly with the application of K. There was no benefit to crown rot disease resistance with increased K fertilization. This study supports that the addition of K to already sufficient soils does not lead to any additional economic benefits and may reduce productivity due to the reduction of B uptake and in vitro digestibility.