IMPACT OF TILLAGE AND LANDSCAPE POSITION ON NITROGEN AVAILABILITY ANDYIELD OF SPRING WHEAT IN THE BROWN SOIL ZONE IN SOUTHWESTERN SASKATCHEWAN

Nitrogen availability to a spring wheat crop was examined in the cropp ing season in a side-by-side comparison of no-till (first year) and ti llage fallow in an undulating farm field in the Brown soil zone in sou thwestern Saskatchewan. Thirty different sampling points along a grid in each tillage landscape were randomly selected, representing 10 each of shoulder, footslope and level landscape positions. Nitrogen availa bility was studied i) by profile inorganic N content ii) by crop N upt ake and yield of spring wheat (Triticum aestivum L.) and iii) by N-15 tracer technique and in situ burial of anion exchange resin membranes (AEM). Pre-seeding available moisture content of the surface soil samp les was significantly higher under no-till compared with tillage fallo w. However, no significant differences in pre-seeding profile total in organic N, crop N uptake and yield were observed between the treatment s. At the landform scale, shoulder positions of the respective tillage systems had lower profile inorganic N, crop N uptake and yield compar ed with other slope positions. Soil N supply power, as determined by N -15 tracer and AEM techniques, was not significantly different between the tillage treatments, indicating that N availability is not likely to be greatly affected in initial years by switching to no-till fallow in these soils under normal moisture conditions.