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

Non-Peer ReviewedDiverse 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

Integration of cultural weed control enhances weed control in organic cropping systems

Non-Peer Reviewe

Weed dynamics under diverse nutrient management and crop rotation practices in the dry zone of Sri Lanka

Integrated weed control strategies are essential for organic and integrated nutrient management, where both systems are progressing with a fundamental of zero or minimum synthetic chemical cultivations. For optimizing the outcome of weed management, a better understanding of the weed dynamic is needed. Especially, with the absence of herbicides, weeds are expected to be controlled by the system itself, during the transition period under rice-based crop rotation systems. This study was conducted to estimate the weed abundance, growth, and composition during the transitional period with conventional (CONV), integrated (INT), and organic (ORG) nutrient management under four crop diversification intensities in a dry zone of Sri Lanka. Monocrop rice and a rice-maize rotation were the starting point. After 1 year, the diversification intensity was increased by adding interseason sunnhemp (rice-sunnhemp-rice and rice-sunnhemp-maize). Weed density and weed biomass were measured at 20 DAS and 60 DAS intervals. Weed density was higher in ORG during the early growth stages of monocrop rice rotation in the 1st cycle, and monocrop rice and rice-sunnhemp-rice rotation in the 2nd cycle while didn’t show any changes during the later growth stage of all systems in both cycles. The total weed biomass in ORG increased with increasing crop diversification. Overall, crop rotation in INT reported the lowest weed density and biomass after two cycles. In the CONV with rice-sunnhemp-maize rotation, weed biomass had declined, while in ORG grass biomass decreased only in sunnhemp cultivated rotations. Overall, INT was the best for weed suppression irrespective of crop rotation intensities. Monoculture with rice in the INT was able to suppress weed more effectively than rice-maize rotation