Soil and Plant Responses to Long‐Term Fertilization of Alfalfa (Medicago sativa L.)1

Synopsis Yields and persistence were greatly increased by K fertilization over a period of 9 years. Yields were not affected and persistence was reduced by N and P. P concentration in alfalfa hay was dependent on rainfall rather than on the P fertilizer. Levels of soil K and P supplies were considerably influenced by K and P. Continued alfalfa production was largely dependent on the relative abundance of K provided by fertilization. P from the soil supply was sufficient for maximum yields, but supply was depleted without application of P.