Range Fertilization: Plant Response and Water Use

During the 10-year study, herbage production on an unfertilized, mixed prairie range site in eastern Montana averaged 1,047 kg/ha and ranged from 720 to 1,321 kg/ha. Elimination of nitrogen (N) and phosphorus (P) deficiencies by fertilizing increased herbage yields an average of 114% (ranging from a low of 32% in a "dry" year to a high of 218% in a "wet" year). Nitrogen was the major growth-limiting plant nutrient with measurable responses to P occurring only when N was nonlimiting. Single high-rate applications were about equal to annual N applications when compared on an annual rate equivalent basis. Species composition varied as much among years as among fertilizer treatments. At N rates of 336 kg/ha or less, cool-season grasses increased in about the same proportion as did forbs and shrubs, maintaining a relatively constant composition of the major species groups. On unfertilized plots, herbage yields and water use reached maximum values of about 1,250 kg/ha and 265 mm, respectively, regardless of further increases in available water. Unfertilized plots produced an average of 2.60 kg/ha for each 1 mm of precipitation received as compared with 5.81 kg/ha on fertilized plots.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.Migrated from OJS platform August 202