Relative influence of crop rotation, tillage, and weed management on weed associations in spring barley cropping systems

Abstract

Generalizations concerning the effects of management practices on weed community dynamics often lack robustness, most likely because of the concomitant effects of agronomic and environmental factors. However, such generalizations, when valid, provide useful grounds for predictions and are thus desirable. This study attempted to evaluate the relative importance of crop rotation, tillage, and weed management as factors affecting weed communities and tested the hypothesis of an association between management practices and weeds from certain life cycle groups. Principal component analysis (PCA) of weed density data from a 4-yr field study conducted on a Kamouraska clay and a Saint-André gravelly sandy loam at La Pocatière QC, Canada, identified groups of weed species, while an analysis of variance (ANOVA) of PCA scores associated these groups with management factors. A multivariate analysis of variance (MANOVA) of regression coefficients describing time courses of density for each species confirmed treatment effects. Species segregated roughly according to life cycles. Interactions among weed management intensity, tillage, and crop rotation mostly explained species dominance in the various cropping systems. A first group of species, mostly annual dicots, largely dominated in minimum weed management treatments; their relative importance in each rotation varied with their level of susceptibility to postemergence herbicides. A second group included annuals and perennials, whose commonality seemed to be their tolerance to herbicides; these species also had a particular affinity for chisel and no-till treatments. A third group was formed by perennial species, each with a different response to tillage. The tenuous correspondence between commonly used classification schemes and management factors suggests that other aspects of weed biology (e.g., seed size, dispersal, production, germination requirements, and seedbank longevity) should be considered when trying to explain and predict the presence and dominance of certain weed species with regard to management practices.

Effect of tillage, cover crop and crop rotation on the composition of weed flora in a sandy soil

“…(1997). Légère & Samson (1999) reported that dominance of certain weeds in particular cropping systems is highly dependent on the interactions of locations, herbicide management, tillage system and crop sequence. Similarly, Doucet et al .…”

“…Hume (1982) documented differences between weed communities in summer fallow–wheat rotation and continuous wheat. Légère & Samson (1999) explained that species dominance in various cropping systems was influenced by interactions among crop rotation, weed management intensity and tillage. Swanton et al .…”

“…Weed community shifts cannot be accounted for by a single variable because communities are influenced by multiple abiotic and biotic factors (Légère & Samson, 1999). Agronomic and environmental factors, such as crop rotation, tillage, cover crops, soil type, moisture, herbicide use, etc., all affect weed communities (Hume et al ., 1991;Dale et al ., 1992; Derksen et al ., 1993).…”

Continuous cropping systems and weed selection

“…Furthermore, if data are available for more than one management regime, then simulations can examine the implications of rotations of management conditions (Cussans & Moss, 1982). However, prediction of the shifts in weed communities is inherently difficult due to the complex interactions involved (Derksen et al, , 2002Légère & Samson, 1999). Specific responses of weeds to management practices are difficult to generalise because of incomplete understanding of the biology of some weed species, the numerous confounding of factors in cropping systems studies, and the impact of environmental factors.…”

Response of weed flora to combinations of reduced tillage, biocide application and fertilization practices in a 3‐year crop rotation

“…Integrating more than one conservational practice may improve sustainability, while offering the potential for reducing problems caused by a single conservational practice. Some studies have examined the effects of combinations of: tillage systems and weed management on dominant species (Légère & Samson 1999); tillage systems and fertilization sources and rates on species diversity and composition (Stevenson et al . 1997; Swanton et al .…”