EFFECT OF NATIVE PRAIRIE, CRESTED WHEATGRASS (AGROPYRON-CRISTATUM (L) GAERTN) AND RUSSIAN WILDRYE (ELYMUS-JUNCEUS FISCH) ON SOIL CHEMICAL-PROPERTIES

Crested wheatgrass and Russian wildrye are used extensively as seeded pastures in the prairie region of western Canada, Their long-term impact on soil quality was studied at 4 sites, each including plant communities of native mixed prairie rangeland and 17- to 27-year-old monocultures of crested wheatgrass and Russian wildrye, in southern Alberta, Canada, Root mass and soil chemical properties were determined on the soil samples collected, Native rangeland had about 7.6 times more root mass than the seeded species from the 0- to 7.5-cm depth and about equivalent mass from the 7.5- to 40-cm depth, For the seeded species, root mass was significantly less between rows than within rows, Soils in the native rangeland community had significantly greater soil organic matter and lower NO3-N, chemical index, urease activity, and available phosphorus than those in the seeded pastures, Altering the plant community from native mixed prairie to either a sequence of cropping followed by an introduced grass monoculture, or directly to an introduced grass monoculture, resulted in decreased root mass and organic matter, and monosaccharide content of dry aggregates, The seeded grasses could neither return nor maintain the chemical quality of the soils in relation to that of the native rangeland.