Schoofs, A. and Entz, M. H. 2000. Influence of annual forages on weed dynamics in a cropping system. Can. J. Plant Sci. 80: [187][188][189][190][191][192][193][194][195][196][197][198]. Alternatives to herbicides are needed for weed control. Field studies were conducted in 1994/1995 and 1995/1996 to investigate the nature of forage crop-weed dynamics and to test the effect of single year forage crops on the density and community composition of annual weeds in a following field pea (Pisium sativum L.) test crop. Five spring-seeded forage treatments were compared with wheat (Triticum aestivum L.) grain crops (with or without herbicides for grassy and broadleaved weeds): winter triticale (Triticosecale) (simulation grazed); spring triticale (silage); spring/winter triticale intercrop (silage, then simulation grazed); alfalfa (Medicago sativa L.) (hay); sorghum-sudangrass (Sorghum bicolor [L.] Moench × Sorghum sudanese [Piper]) (hay); and a weedy fallow (silage). A fall rye (Secale cereale L.) grain crop and a sweet clover (Melilotis officinalis L.)/winter triticale double crop (hay, then simulation grazing) were included in the 1995/1996 trial. All forage systems were at least as effective as the sprayed wheat control in suppressing wild oat (Avena fatua L.); however, effects on other weeds, especially broadleaved species, were variable. Biennial crops provided the best early season weed control, while long-season systems such winter triticale and the triticale intercrop provided the best late season weed control. Forages shifted the weed community composition away from wild oat and green foxtail (Setaria viridis L. Beauv.) to a similar or greater extent than herbicide-treated wheat. Forage systems that did not provide season-long crop competition tended to have more broadleaved weeds. Some forage systems increased pea grain yield the following year (relative to the sprayed wheat control); however, forages alone did not eliminate the need for herbicides in the pea crop. Annual forages may play an important role in integrated weed management, especially for wild oat, however further research to refine forage-based weed management systems is needed. Tous les systèmes fourragers annuels se sont révélés au moins aussi efficaces que le blé désherbé chimiquement pour maîtriser la folle avoine (Avena fatua L.), mais pour ce qui est des autres mauvaises herbes, particulièrement les dicotylédones, les effets étaient variables. Ce sont les cultures bisannuelles qui procuraient la meilleure maîtrise des mauvaises herbes en début de saison et les cultures de saison longue comme le triticale (hiver ou printemps-hiver) la meilleure en fin de saison. La présence de la sole fourragère dans la rotation éloignait la composition floristique des adventices de la dominance folle avoine-sétaire verte (Setaria viridis L. Beauv.) dans une mesure au moins égale à celle causée par le blé désherbé chimiquement. Les traitements fourragers qui ne fournissaient pas une compétition culturale continue tout au long de l'année renfermaient en gén...

No abstract

Pesticide Free Production (PFP) is a pesticide reduction system that removes in-crop pesticide use on a yearly basis. A longterm study was established in 2000 to investigate the effect of crop rotation and frequency of inclusion on the success of PFP, as well as the effect of PFP on subsequent crops in the rotation. The crop rotations being compared were linola-oat-canola-wheat and linola-oat-alfalfa-alfalfa. PFP occurred either once in the rotation (oat) or twice (linola-oat). Weed density and yield were measured in the crops that followed PFP. Oat was a more successful PFP crop than linola because it was better able to compete with weeds. Furthermore, PFP oat had a higher weed density when it followed PFP linola, but this did not influence PFP oat yield. Under the conditions of this study, PFP linola was more successful in the annual crop rotation. Inclusion of alfalfa hay crops in the crop rotation was not effective in lowering weed pressure and, in fact, may have contributed to an increase in weed density. It is concluded that weed species present influenced the effectiveness of alfalfa in facilitating PFP, because major weeds in the study are not effectively controlled by alfalfa. PFP did not have a negative effect on following crops in the rotation (i.e. canola-wheat or alfalfa), regardless of whether one or two consecutive years of PFP occurred in the rotation. No additional herbicide was necessary for weed control in the crops that followed PFP; however, alfalfa hay was weedier for the first year following PFP. This study indicates that PFP is a viable way to reduce herbicide use in a cropping system and that attention needs to be paid to PFP crop selection and crop rotation, particularly when the PFP crop is less competitive with weeds.

Strategies for pesticide use reduction have suffered from limited adoption. The impact of such strategies will be greater if they appeal to farmers with typical demographics and attitudes. A participatory, on-farm study was conducted to assess the potential of Pesticide Free ProductionTM (PFP) [Pesticide Free ProductionTM and PFPTM are registered trademarks of the University of Manitoba.] to be widely implemented on mainstream farms in Manitoba, Canada. PFP is a flexible, simple framework intended to appeal broadly to farmers who may not have adopted other pesticide use reduction initiatives. It may also provide a marketable food product label. This novel crop production system prohibits the use of in-crop pesticides and seed treatments during one crop year, as well as prior use of residual pesticides. Applications of nonresidual pesticides (such as glyphosate) are permitted prior to crop emergence. Synthetic fertilizer use is permitted at any time. The objectives of this study were: (1) to determine if the demographic and attitudinal characteristics of farms and farmers participating in a PFP pilot project varied depending on the level of PFP implementation; and (2) to compare the characteristics of farms and farmers participating in the pilot project with standards representing average farms and farmers in Manitoba. A total of 71 farmers, representing 120 fields and 11 crops, participated in the study. Fields and farmers were categorized into three groups, based on whether or not fields: (1) achieved PFP certification status and (2) were in transition to organic production. There were few demographic differences among groups. Demographic characteristics of participating farmers were typical for Manitoba, with the exception that participating farmers who were not in transition to organic production had higher levels of education than a random sample of Manitoba farmers. Attitudinal orientation (adherence to a conventional versus an alternative agricultural paradigm) of participants who were not in transition to organic production was similar to that of a random sample of Manitoba farmers. Fields and farms on which PFP was implemented were relatively large in the context of Manitoba averages. Participants indicated high satisfaction with certifiable PFP crops and high levels of interest in implementing future PFP. Pesticide free production demonstrates significant potential for broad adoption in this region.

Existing strategies for pesticide use reduction in the northern Great Plains have suffered from limited adoption. A novel approach, Pesticide Free Production (PFP), was recently developed in Manitoba, Canada. A participatory, on‐farm study was conducted to assess the potential of PFP to be implemented on typical farms and the level of success farmers experienced with PFP. Pesticide Free Production prohibits the use of in‐crop pesticide and seed treatments during one crop year as well as prior use of residual pesticides. Synthetic fertilizer use is permitted, as are pre‐emergent applications of nonresidual pesticides. A total of 71 farmers, representing 120 fields and 11 crops, participated in the study. Fields and farmers were grouped based on whether or not fields (i) achieved PFP certification and (ii) were in transition to organic production. Certification was achieved for 83% of the participating area. Spring cereals were the most likely crops to achieve PFP certification. Yields in all groups were slightly lower than conventional averages in Manitoba but were not significantly different among groups. Weed densities were higher (P = 0.065) in noncertifiable fields than in certifiable fields. Most farmers reported manageable weed densities in the year following PFP. Soil conservation practices were used on a high proportion of PFP fields. Management practices associated with PFP included the use of delayed seeding, forages in rotation, and increased seeding rates. Agronomic and demographic characteristics of participating fields and farmers were typical for Manitoba. Pesticide Free Production demonstrates considerable potential to be successfully adopted by mainstream farmers.