C.A. Grant and D.A. Derksen

Agriculture and Agri-Food Canada, Brandon Research Centre, Brandon, MB, Canada

While there is a great deal of good information available indicating that row spacing can be increased to 12 inches in no-till systems without negative effects on crop yield, problems may arise when canola is seeded on wide row spacing with side-banded urea fertilizer. By increasing row spacing, the concentration of fertilizer present beside the seed-row is increased. With small-seeded crops such as canola, which tend to be sensitive to seed-fertilizer contact, this may lead to seedling toxicity, even where the fertilizer is separated from the seedling by the recommended 1-inch by 1-inch side-banded pattern. Toxicity may be accentuated if the separation between seed and fertilizer is compromised due to "bounce" of the seed and fertilizer during the seeding operation.

Co-operative studies are being conducted across western Canada evaluating the impact of urea nitrogen timing, placement and row spacing on canola and wheat yield and weed competition. The most consistently effective treatment in this study has been the 9-inch row spacing with side-banded urea application. In 4 of 7 site years of canola and 2 of 7 site-years of wheat, yield was lower with 12-inch row spacing and side-banded urea nitrogen as compared to the 9-inch row-spacing treatment. The problems with the 12-inch row spacing appear to be due to seedling damage from the side-banded urea. Problems with seedling toxicity are likely to be greater on high pH, carbonated soils, on coarse-textured soils, or with dry soil conditions after seeding. High pH carbonated soils are more frequent in the eastern prairies than in more westerly regions.

Studies conducted in 1998 at a number of locations across western Canada took a closer look at the effect of row spacing at different rates of urea N. While there was generally little difference between 9-inch and 12-inch spacing at most of the sites, the 9-inch spacing produced higher stand density and higher yields than the 12-inch spacing at the Brandon location. This indicates that while seedling damage will not always occur, there are situations where the effect may be significant, depending on soil and environmental conditions.

Studies are continuing across western Canada to more clearly evaluate the impact of row spacing and fertilizer placement on yield, quality and competitive ability of canola and wheat. This should help to clarify factors contributing to damage and develop management practices that will optimise economics of crop production in one-pass seeding systems.