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Winter canola (Brassica napus L.) production has increased in the Great Plains as producers seek a rotational and alternative crop to winter wheat (Triticum aestivum L). However, limited information is available if canola could be used for dual‐purpose without significantly affecting grain yield. The objectives of this study were to (a) investigate dual‐purpose potential and (b) impact of companion crops on growth, survival, biomass, and grain yield of canola. The study was conducted in 2011 and 2012 at Garden City, KS. The experimental design of the study was a randomized complete block design with split‐plot arrangement. Main plot treatments were a factorial of canola cultivars (Griffin or Wichita) and companion crop treatments (none, spring triticale [× Triticosecale Wittm. ex A. Camus], winter triticale, radish [Raphanus raphanistrum subsp. sativus (L.) Domin], and turnip [Brassica rapa var. rapa L.]), and the split‐plot treatments were single‐purpose (grain only) or dual‐purpose (grain and forage) management. Averaged across cultivars and years, grain yield was 70% greater when canola was used for single‐purpose (grain‐only) compared with dual‐purpose. Griffin grain yield tended to be relatively greater than Wichita in dual‐purpose use. Averaged across the two years, turnip as a companion crop decreased canola yield by 38% but resulted in greater forage accumulation. In conclusion, dual‐purpose canola has a grain yield penalty, but effects may vary by cultivar. Companion cropping did not benefit canola and in some cases negatively affected grain yield. When grain production is the primary objective, both companion cropping and forage use should be avoided. [ABSTRACT FROM AUTHOR]

Including winter canola (Brassica napus L.) crop into cereal-based crop rotations can diversify the current agricultural systems in the United States (US). In addition, canola can help to satisfy market demand for plant-based edible oil, thus better understanding of oil productivity of canola in the US production areas is relevant for further study. Canola seed oil concentration is a function of the genotype (G), environment (E), management (M), and their interaction (G × E × M). The overall aim of this research study was to identify suitable production environments with increased canola seed oil concentration and opportunities to increase cropland area in the US. The objectives of this research were: i) characterize the environmental variability of seed oil concentration in the National Winter Canola Variety Trials (NWCVT), ii) identify geographical regions and states within the continental US with potential for production of winter canola with high seed oil concentration and the link with yield, and iii) explore the potential development of varieties with stable high seed oil concentration and high yield. In this study, the E component accounted for 75% of the total variation in seed oil concentration, with the G factor only explaining 8%. Overall, seed oil concentration averaged 398 g kg-1 but ranged from 311 to 461 g kg-1. The US Midwest and Great Plains regions were shown to have a greater frequency of medium (> 389 g kg-1) and high canola seed oil concentration (> 411 g kg-1). Genotypic variation for both seed oil concentration and yield was found with an opportunity to achieve high oil and yield under varying environments. Our findings suggests that there is significant potential to further expand the area of canola cropland to increase oil productivity and focus should be on breeding high yielding varieties with stable high seed oil concentration. • Environment explained most of the oil concentration variability in winter canola. • Precipitation and photothermal quotient explain the oil concentration variability. • Large winter canola production area with potential for high oil concentration in US. • Potential to develop varieties with stable high seed oil concentration and yield. [ABSTRACT FROM AUTHOR]