Oilseeds for improving agronomic and environmental sustainability of wheat-fallow rotation

Authors: ZHELJAZKOV, VALTCO - Oregon State University; Evangelista, Roque

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract Only
Publication Acceptance Date: 8/27/2023
Publication Date: 8/27/2023
Citation: Zheljazkov, V., Evangelista, R.L. 2023. Oilseeds for improving agronomic and environmental sustainability of wheat-fallow rotation [abstract]. Association for the Advancement of Industrial Crops Conference. p. 82.

Interpretive Summary:

Technical Abstract: Dryland winter wheat production in large areas of the Palouse region, which includes parts of southeastern Washington, north central Idaho, and northeast Oregon, is primarily based on a wheat-fallow rotation. In this system, wheat is grown once every two years, with 10 months dedicated to fall-sown wheat and 14 months of fallow period (either conventional or direct seed system). This wheat/fallow rotation has been practiced for over a century, as the 14-month fallow period allows the soil to conserve moisture and store winter precipitation, which is crucial for the wheat crop in the following season. However, this system results in a crop being grown only every other year, leaving the ground bare or under chemical fallow for an extended period and causing environmental issues. The hypothesis of this study was that the current dryland winter wheat-fallow rotation could be enhanced by introducing an additional cash crop and transitioning to a three-year rotation: winter wheat/cash crop/fallow. We evaluated the agronomic and environmental feasibility of including 12 crops suitable for biodiesel and high-value chemical production in the existing winter wheat-fallow rotation. These crops included canola (Brassica napus), oriental mustard (Brassica juncea), camelina (Camelina sativa), safflower (Carthamus tinctorius), sunflower (Helianthus annuus), flax (Linum usitatissimum), coriander (Coriandrum sativum), caraway (Carum carvi), cumin (Cuminum cyminum), anise (Pimpinella anisum), dill (Anethum graveolens), and fennel (Foeniculum vulgare). The evaluation was conducted at two locations: Pendleton, OR, and Moro, OR, characterized with 15- and 12-inches annual rainfall, respectively. We analyzed and presented data on seed yield, oil content and fatty acid (FA) composition, and essential oil yield. Overall, there was significant variation in oil content (measured by pNMR), fatty acid composition, essential oil content and yield, and biodiesel yield among the different crops and within a single crop depending on the location. However, with the exception of camelina, most oilseed crops did not perform well after winter wheat at the Moro location, which receives an annual rainfall of 12 inches. Therefore, it can be concluded that incorporating oilseeds for biofuel and high-value chemical production into the dryland winter wheat-fallow rotation can enhance agronomic and environmental sustainability in areas where the annual rainfall exceeds 15 inches.