An assessment of the concept of early time of weed removal in field pea using natural weed populations

Abstract

The economic and agronomic benefits of including annual grain legumes in cropping systems has resulted in a large increase in field pea production in Western Canada. Concerns have been raised about the large year-to-year variability in field pea grain yields and recent attention has focussed on weed management. A study was conducted to quantify the effects of time of post-emergence herbicide application to normal leafed and semi-leafless field pea types under natural weed populations and conservation tillage practices. Odyssey™ herbicide (50:50 imazethapyr:imazamox) was applied either 1, 2 or 3 wk after crop emergence with an untreated check included. The study was conducted at seven locations across the major agro-ecological zones of Saskatchewan in 1999 and 2000. The results of this study support the merits of early herbicide application 1 to 2 wk after crop emergence. Benefits of early time of weed removal occurred in 7 of 14 sites-years. There was no yield penalty recorded from early applications of herbicide, but some yield penalty was observed with later applications at certain locations. Spraying early rather than late minimizes the risks associated with delayed applications resulting from adverse weather conditions and a possible decrease in crop tolerance as was observed at the Swift Current site. Results support the early removal of weeds from field pea crops to optimize seed yield. Key words: Crop-weed interference, Pisum sativum L., weed management, timing of herbicide application