Crop–weed interactions under diverse cropping systems in the Canadian prairies

Abstract

Diverse cropping systems with different input levels and crop diversities can alter weed community dynamics (abundance and crop-weed competition). Organic systems believed to have greater heterogeneity in soil resources which can sustain more competition form weeds compared to conventional systems. However, direct evaluation of competitiveness among the two systems under wide range of crop diversities has not being tested. Therefore, a study was carried out within a long-term cropping systems study at Scott, Saskatchewan to compare weed dynamics. The main experiment consists of three input levels; high, reduced, and organic and three diversity levels; low, diversified annuals, diversified annual perennials. A micro-plot study was carried out within the main experiment with four weed control treatments applied in the wheat phase of reduced and organic systems. The treatments were 1.weed free treatment, 2. weedy treatment, 3. standard weed control and 4. pseudo weed established at 1:1 ratio with the crop. Within organic crop rotations weed density was high in diversified annual perennial system while in reduced systems it was high in diversified annual grain rotations. Overall, diversified annual perennial system had low weed biomass compared to low diversity rotation. There was no difference in weed biomass between organic and reduced systems. There was no difference between organic and reduced systems for yield loss. Grain yield was greater in reduced compared to organic systems. Even under weed-free conditions grain yield was low in organic systems indicating weeds are not the major yield limiting factor in Saskatchewan organic cropping systems.