Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2012
Publication Date: 10/2/2012
Citation: Nord, E., Ryan, M.R., Curran, W.R., Mortensen, D.R., Mirsky, S.B. 2012. Effects of management type and timing on weed suppression in soybean no-till planted into rolled-crimped cereal rye. Weed Science. 60(4):624-633. Interpretive Summary: No-till soybean production has been widely adopted by conventional producers, however concerns with weed resistance and potential nontarget herbicide environmental toxicity have spawned interest in reducing chemical inputs, diversifying weed selection pressures, and developing reduced-tillage organic soybean cropping systems. Therefore, we conducted an experiment to examine the role of cover cropping on weed suppression in soybean. Specifically, we examined the effects of weed management system (organic vs. conventional), timing of cover crop fall planting date and spring termination date, and supplemental control (herbicides or high residue cultivation) on weed suppression and community composition in soybean no-till planted into a cereal rye cover crop. In general, weed control was significantly higher in the conventionally managed cropping systems regardless of rye management timing. Interestingly, at similar cereal rye biomass levels, delay in cover crop management resulted in an increase in weed biomass in the organic system and a decrease in the conventional. Strategies that improve cereal rye weed suppression potential early in the spring are needed since weeds emerging prior to cereal rye termination appear to have the greatest impact on crop performance. This work helps illustrate key principles in integrated weed management and informs producers on strategies for combating herbicide resistant weeds. In addition, this work provides an approach to improve weed management in reduced tillage organic soybean production.
Technical Abstract: Knowledge of weed emergence periodicity can inform the timing and choice of weed management tactics. We tested the effects of weed management system (conventional = CNV and organic = ORG), timing of rye sowing (2 times), timing of soybean planting (5 times, 3 in each system), and supplemental control (with and without) on weed suppression and weed community composition in soybean no-till planted into a cereal rye cover crop. Cereal rye was terminated with a roller-crimper and herbicide (CNV) or with a roller-crimper alone (ORG) and supplemental weed control was achieved with a postemergence glyphosate application (CNV) or with inter-row high-residue cultivation (ORG). Supplemental control in CNV was more effective than in ORG. When soybean was planted on the same date, CNV resulted in less weed biomass and a more even community composition; whereas ORG resulted in greater weed biomass, dominated by common ragweed. When we controlled for cereal rye biomass and compared the effects of planting date within each system, later planting resulted in lower weed biomass in CNV, but greater weed biomass in ORG. Our results suggest the ability of a management system to suppress weed growth prior to soybean planting should be considered when optimizing planting date for weed suppression in no-till soybean.