The germination and emergence of a seedling, or seedling recruitment remains an essential process in the establishment of a plant. This establishment can be limited by the availability of microsites within the soil profile, or the availability of seed within a given area. Three field experiments were initiated in Saskatchewan, Canada to examine the relative effect of seed and microsite limitations on weed seedling recruitment. The first experiment examined the effect of landscape position as well as nitrogen (N) rate and tillage system (zero tillage vs. conventional tillage) on weed seedling recruitment from an indigenous weed population. Survey results indicated habitat differentiation of the weed population with wild oat and cleavers preferentially recruiting in the lower landscape positions, Russian thistle and Kochia in the upper landscape positions, while green foxtail recruited in high levels on all landscape positions. This suggested that different weed species have different microsite requirements for weed seedling recruitment across contrasting landscape positions. The second field experiment examined the effect of landscape position and moisture availability on weed seedling recruitment from an artificial hand-seeded weed seedbank. This experiment indicated that seed limitation remained a very important factor, but even when irrigated, total seedling recruitment did not reach maximum recruitment, indicating water was not the only limiting resource for weed seedling recruitment. Microsite limitations were greatest on the upper slope position for all species with green foxtail having the greatest overall recruitment of the species across all landscapes and moisture regimes. The third experiment examined the effect of tillage system and density on weed seedling recruitment of wild oat, green foxtail, and wild mustard. Again, weed seedling recruitment remained a function of both microsite and seed limitations as absolute recruitment values increased for each density examined in this experiment. The agronomic significance of microsite limitation was negligible as high weed population numbers occurred for the highest weed seeding densities. Overall, microsite limitations remained negligible in these experiments for arable agriculture with the main influence on weed seedling recruitment most often being seed limitation in the natural seedbank.

The goal of the project was to enhance the period of weed growth prior to seeding in order to reduce weed emergence and weed competition after the crop has been planted. Weed growth was stimulated using either light tillage or by applying nitrogen fertilizer early in the spring. Light disturbance significantly increased pre-seed weed emergence while early applied nitrogen did not appear to have an effect. Post seeding weed emergence levels and weed biomass were similar among the light tillage and early nitrogen treatments. Therefore the goal of decreasing weed competition after seeding was not attained. Future research should focus on long-term strategies to reduce weed populations in field rather than seasonal strategies. / October 2006

The germination and emergence of a seedling, or seedling recruitment remains an essential process in the establishment of a plant. This establishment can be limited by the availability of microsites within the soil profile, or the availability of seed within a given area. Three field experiments were initiated in Saskatchewan, Canada to examine the relative effect of seed and microsite limitations on weed seedling recruitment. The first experiment examined the effect of landscape position as well as nitrogen (N) rate and tillage system (zero tillage vs. conventional tillage) on weed seedling recruitment from an indigenous weed population. Survey results indicated habitat differentiation of the weed population with wild oat and cleavers preferentially recruiting in the lower landscape positions, Russian thistle and Kochia in the upper landscape positions, while green foxtail recruited in high levels on all landscape positions. This suggested that different weed species have different microsite requirements for weed seedling recruitment across contrasting landscape positions. The second field experiment examined the effect of landscape position and moisture availability on weed seedling recruitment from an artificial hand-seeded weed seedbank. This experiment indicated that seed limitation remained a very important factor, but even when irrigated, total seedling recruitment did not reach maximum recruitment, indicating water was not the only limiting resource for weed seedling recruitment. Microsite limitations were greatest on the upper slope position for all species with green foxtail having the greatest overall recruitment of the species across all landscapes and moisture regimes. The third experiment examined the effect of tillage system and density on weed seedling recruitment of wild oat, green foxtail, and wild mustard. Again, weed seedling recruitment remained a function of both microsite and seed limitations as absolute recruitment values increased for each density examined in this experiment. The agronomic significance of microsite limitation was negligible as high weed population numbers occurred for the highest weed seeding densities. Overall, microsite limitations remained negligible in these experiments for arable agriculture with the main influence on weed seedling recruitment most often being seed limitation in the natural seedbank.

The goal of the project was to enhance the period of weed growth prior to seeding in order to reduce weed emergence and weed competition after the crop has been planted. Weed growth was stimulated using either light tillage or by applying nitrogen fertilizer early in the spring. Light disturbance significantly increased pre-seed weed emergence while early applied nitrogen did not appear to have an effect. Post seeding weed emergence levels and weed biomass were similar among the light tillage and early nitrogen treatments. Therefore the goal of decreasing weed competition after seeding was not attained. Future research should focus on long-term strategies to reduce weed populations in field rather than seasonal strategies.

The goal of the project was to enhance the period of weed growth prior to seeding in order to reduce weed emergence and weed competition after the crop has been planted. Weed growth was stimulated using either light tillage or by applying nitrogen fertilizer early in the spring. Light disturbance significantly increased pre-seed weed emergence while early applied nitrogen did not appear to have an effect. Post seeding weed emergence levels and weed biomass were similar among the light tillage and early nitrogen treatments. Therefore the goal of decreasing weed competition after seeding was not attained. Future research should focus on long-term strategies to reduce weed populations in field rather than seasonal strategies.