Crop Seeding Rate Influences the Performance of Variable Herbicide Rates in a Canola–Barley–Canola Rotation

Abstract

Glyphosate-resistant canola was seeded at Vegreville, Alberta, in 1997 and 1999 and barley in rotation with the canola in 1998 at three seeding rates. The effects, at each crop seeding rate, of variable glyphosate (canola) and tralkoxydim plus bromoxynil plus MCPA (barley) rates on crop yield, net economic return and seed production by wild oat, wild mustard, and wild buckwheat, and the amount of weed seed in the soil seed bank was determined. Crop seeding rate influenced the response of canola and barley yield and weed seed production to herbicide rate. At the lowest crop seeding rates, yield responses tended to be parabolic with yields increasing up to one-half and three-quarters of the recommended herbicide rates and trends toward reduced yields at the full rates. This response was not evident at the higher crop seeding rates, where, in most cases the yield reached a maximum between one-half and the full recommended rate. The effects of the herbicides on weed seed production, especially at the lowest rate, were often superior at the higher crop seeding rates. The results indicate that seeding canola and barley at relatively high rates may reduce risk associated with lower crop yields and increased weed seed production at lower than recommended herbicide rates. However, the current cost of herbicide-resistant canola seed may preclude the adoption of this integrated weed management practice by growers.

Impact of Conyza bonariensis density and establishment period on soyabean grain yield, yield components and economic threshold

“…These experiments demonstrate the need for appropriate weed control tactics to eliminate C. bonariensis plants prior to soyabean sowing. Also, they indicate the importance of using residual herbicides at the time of the crop sowing to limit the emergence of C. bonariensis plants (O'Donovan et al ., ; Oliveira Neto et al ., ). Another aspect to consider is the impact of each plant on the weed seedbank.…”

Variable crop plant establishment contributes to differences in competitiveness with wild oat among cereal varieties

“…Enhancing crop competitiveness through the use of competitive varieties and/or relatively high crop seeding rates is an important component of integrated weed management and can improve herbicide performance in spring barley (O'Donovan et al 2001), spring wheat (Hucl 1998), winter wheat (Christensen 1994) and canola (Brassica napus L.) (Harker et al 2003;O'Donovan et al 2004). Cereal and oilseed crop varieties are routinely developed for western Canada, usually with the aim of improving yield, quality and disease resistance, but rarely to improve competitiveness with weeds.…”

Perspectives of oilseed rape as a bioenergy crop

“…The use of oilseed rape as a rotational crop in continuous cereal crop system also makes weed control easier and encourages producers to adopt no tillage practices to prevent soil erosions [14][15][16][17][18][19]. It is even more so when glyphosateresistant oilseed rape is introduced into the cropping system [20][21][22][23]. Along with those benefits of oilseed rape as a rotational crop, controlling volunteer oilseed rape in subsequent crops becomes a major issue [24][25][26], especially with controlling glyphosate-resistant volunteer oilseed rape [27][28][29][30][31][32].…”