ALFALFA GRASS RESPONSE TO NITROGEN AND PHOSPHORUS APPLICATIONS

Alfalfa/grass (Medicago sativa/Dactylis glomerata, Bromus) yield and q uality responses to nitrogen (N) and phosphorus (P) fertilizer appli- cations are well documented, The magnitude of the P response and in tu rn N, may however, be limited by the relative immobility of P in the s oil. A two-year field study was conducted to determine the response of an established alfalfa/grass stand to combinations of a one-time broa dcast application of N, P, and sulfur (S) rates with fall or spring ap plications of P, Nitrogen and P applications increased forage producti on, nutrient concentration and nutrient content, particularly in the f irst production year. No S response was observed. Fall P applications were superior to spring applications only in the first year of product ion. If annual broadcast applications of P are made to existing alfalf a/grass stands in Intermountain areas, fall applications are recommend ed.