Agronomic and economic responses to integrated weed management systems and fungicide in a wheat-canola-barley-pea rotation

Changes in tillage intensity and herbicide use can influence the incidence of weeds, insects and diseases, crop yields and economic returns. We examined the effects of six integrated weed management systems (with varying combinations of tillage methods, seeding rate, seeding date, time when weed control was applied, and annual fungicide applications on pest incidence, grain yield and quality, and economic returns for a spring wheat (Triticum aestivum L.)-canola (Brassica napus L.)-barley (Hordeum vulgare L.)-pea (Pisum sativum L.) rotation in the Dark Brown soils of the Moist Mixed Grassland Ecoregion of Saskatchewan. Herbicide use intensity was reduced without a significant increase in weed biomass in five of the six systems in most crops and years. The complete elimination of herbicides in one system resulted in significant crop yield losses. Certain insects were more prevalent in the cropping systems with early planting dates. Zero tillage systems produced higher yields, and yields generally declined as tillage intensity increased. For all crops, the high herbicide-zero tillage system produced the highest yields, whereas the lowest yields were obtained in the no herbicide-high tillage system. Management method had minimal impact on seed quality. Application of fungicide generally increased yields of barley, wheat and pea, but the increases were not sufficient to recover fungicide cost. High herbicide-zero tillage, medium herbicide-zero tillage, and low herbicide-zero tillage systems produced the highest net return and no herbicide-high tillage system the lowest net return, under all grain price scenarios. Key words: Agronomic, economic, tillage, herbicide, fungicide, weed management systems, weed, insect, disease