AbstractNitrogen fertilization is an essential management component of intermountain hay meadows. Insufficient studies have been conducted to determine the economic feasibility of the 67 to 90 kg N ha−1 typically applied by the producer. The objectives of this study were to estimate forage yield response functions and to determine the economic optimum levels of N application. Forage response to N fertilization data were collected in intermountain meadows in Wyoming during the period of 1965 to 1980. The three meadow types investigated were native, improved grass and grass‐alfalfa (Medicago sativa L.) mixtures with 29, 10, and 16 field trials, respectively. Application rates for the N fertilizers ranged from 0 to 180 kg ha−1. The yield response equations were used to determine the economic optimum level of N application for three alternative prices for hay and N fertilizer. The mean economic optimum level of N application for the three price levels was 149,161, and 101 kg N ha−1 on native, improved grass, and grass‐alfalfa meadows, respectively. The improved grass species demonstrated a greater response to the higher levels of N than the other two meadow types. This study indicates that average producers are applying N to intermountain hay meadows at average rates considerably below the economic optimum. Assuming a net hay price of $55 Mg−1 and an N price of $61.60 100−1 kg, the returns ha−1 over fertilizer and harvest costs could be increased $15, $19, and $1 ha−1 for native, improved grass, and grass‐alfalfa meadows, respectively, if the economic optimum N rates were applied as compared to the typical level of 90 kg ha−1.