Shortage of available nutrients is limiting productiveness of native range in portions of the northern Great Plains. The demand for increased forage production to support an increasing number of livestock will require use of intensive management practices, including range fertilization.
Response of mixed prairie vegetation to annual applications of 0, 45, 90, and 180 kg elemental N/ha and 0, 20, and 40 kg elemental P/ha was studied over an 8‐year period near Mandan, N. D. At all P levels and for each harvest height used, increase in dry matter production in response to N was highly significant and nearly linear in nature for the 45‐N and 90‐N levels. Harvest at a height of 25 mm on August 1 produced 8‐year average annual dry matter yields of 810, 1,938, 2,960, and 3.097 kg/ha for the 0‐N, 45‐N, 90‐N, and 180‐N levels, respectively. Harvest at the soil surface produced 6‐year average yields of 2,047, 3,035, 3,898, and 4,205 kg/ha for the respective N levels. Response to P was often not significant during the first 3 years of the study; however, ever the 8‐year period, each increment of P produced a significant yield increase. Without N, response to P was small, but as N level increased, response to P increased. Density of western wheatgrass (Agropyron smithii Rydb.) increased and basal cover of blue grama (Bouteloua gracilis [H.B.H.] Lag.) decreased as N level increased under the harvest system used in this study.
