EFFICACY OF INORGANIC FERTILIZERS IN RESTORING WHEAT YIELDS ON ARTIFICIALLY ERODED SOILS

Chemical fertilizers are often used to amend eroded agricultural land. However, the relationships between level of erosion, nitrogen (N) rat e and phosphorus (P) rate in restoring soil productivity are unclear. In 1990, experiments were initiated to examine the effect of three lev els of erosion (0, 10 and 20 cm of topsoil removal to simulate non-ero ded, moderately eroded and severely eroded soils), four rates of N and three rates of P on the performance of spring wheat (Triticum aestivu m L.) for four southern Alberta soils. Residual erosion and fertilizer effects were assessed in a second cropped year. Erosion significantly decreased grain and straw yield at all four sites in the initial year . Removing 10 and 20 cm of topsoil reduced non-fertilized production b y 43-66% and 60-85%, respectively, as compared with the undisturbed no n-fertilized plots. Except for one site in the initial year, additions of N and P only partly remedied these losses. Responses to N and P we re highest at moderate levels of erosion at three sites. There was a g reater yield overlap between moderately and severely eroded treatments than between non-eroded and moderately eroded treatments, implying th at the restoration of productivity is more difficult once the shallowe st layer of topsoil has been removed.