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Little information has been published concerning the long-term effects of N and P fertilization on nutrient cycling and availability of N and P as related to quantity and quality of native grassland herbage. Factorial combinations of ammonium nitrate at rates of 0, 112, 336, and 1,008 kg N/ha and concentrated superphosphate at rates of 0, 112, and 224 kg P/ha were broadcast once in the spring of 1969 on a native range site (Bouteloua-Carex [Stipa] faciation of a mixed prairie association). During the next 8-years, plant N and P content of grasses and nongrasses increased for periods of time proportionated to the rate of N and P applied. Plant N content tended to be low in "wet" years and relatively high in "dry" years. Conversely, plant P content ended to be high in "wet" years and relatively low in "dry" years. After the first 2 years, the increase in plant N and P uptake, resulting from a given level of N-P fertilization, continued at a rather stable rate as compared with the unfertilized check. In 1973, the unfertilized check had 20,700 kg/ha of root material in the upper 30 cm of soil. The fertilized (336 kg N/ha plus 224 kg P/ha) grassland had 24,310 kg/ha of root material which contained 116 kg/ha more N and 8 kg/ha more P than did the check. Therefore, the below-ground root system is a nutrient-deficient sink which has a high potential to immobilize relatively large quantities of applied N and P fertilizer materials. This study revealed the long-term benefits of N and P fertilization on forage quality which may persist for several years after yield responses are no longer apparent. 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 2020