Comparative nitrogen partitioning and water use by native and introduced grass communities in southern Alberta, Canada

Abstract

The objectives of this research were to evaluate 1) short-term changes in soil and plant N partitioning created by cultivating and re-seeding native grasslands with two cropping systems of wheat and perennial (crested wheatgrass and Russian wildrye) monocultures; 2) differences in the rate of soil water uptake between Mixed Prairie grasslands, crested wheatgrass and Russian wildrye after a dry-down period; and 3) differences in above ground water use efficiencies, root and crown masses between Mixed Prairie grasslands, crested wheatgrass and Russian wildrye under two different soil water contents. The perennial agronomic species were recommended by Agriculture and Agrifood Canada for seeding in Mixed Prairie and Fescue grassland in southern Alberta, Canada. In the first four years after plow-down, soil nitrate (NO3 -) concentration was higher and light fraction N (LFN) was lower in the soil under wheat than native grasslands. Although LFN was lower in perennial monocultures than native grasslands, there was little difference in soil nitrate. More N was partitioned into shoot biomass of wheat, crested wheatgrass and bromegrass that native grasslands and levels increased as annual and long-term growing season precipitation increased. There were no differences in the rate of soil water uptake after dry-down periods between native Mixed Prairie, crested wheatgrass or Russian wildrye, but both perennial monocultures had higher above ground water use efficiencies than native Mixed Prairie.