Continuous Winter Wheat Versus a Winter Canola–Winter Wheat Rotation

Abstract

Difficult to control winter annual grasses that have been used to produce forage, especially Italian ryegrass (Lolium multiflorum Lam.) and feral rye (Secale cereale L.), have invaded Oklahoma fields traditionally used to produce continuous winter wheat (Triticum aestivum L.). This study was conducted to determine whether a winter canola (Brassica napus L.)–winter wheat crop rotation could compete economically with continuous winter wheat. The effects of seven herbicide treatments for continuous wheat and 24 herbicide treatments for the canola–wheat rotations were analyzed during a rotation cycle at four Oklahoma locations. Enterprise budgets were prepared to enable economic comparisons across production systems and treatments. Wheat yields in the second year of the canola–wheat rotations were significantly (P < 0.05) greater than wheat yields in the second year of continuous wheat across all four locations (10, 11, 15, and 22%). Based on the historical relationship between wheat and canola prices, and a wheat price of US.21 kg−1 and a canola price of US.40 kg−1, for the three sites for which net returns could be pooled across herbicide treatments, net returns from the canola–wheat rotation (US$197, US$123, and US$24 ha−1 yr−1) were significantly (P < 0.05) greater than net returns from continuous wheat (–US$46, –US$118, and –US$48 ha−1yr−1). Based on historical price relationships and the yields produced in the trials, a winter canola–winter wheat crop rotation may improve net returns relative to continuous winter wheat for Oklahoma fields infested with Italian ryegrass and feral rye.