Location: Food Systems Research UnitTitle: Surmounting the tradeoff between productivity and weather resilience in diversified grain rotations
Submitted to: AgriRXiv
Publication Type: Pre-print Publication
Publication Acceptance Date: 10/5/2023
Publication Date: 10/5/2023
Citation: Ewing, P.M., Chim, B.K., Lehman, R.M., Osborne, S.L. 2023. Surmounting the tradeoff between productivity and weather resilience in diversified grain rotations. AgriRXiv. https://doi.org/10.31220/agriRxiv.2023.00202.
Interpretive Summary: The crop rotation is a critical management choice that growers make that dictates farm productivity and viability. In the US and globally, rotations have become less diverse over the past 50-100 years as yields have increased. Because increasingly extreme weather is threating this productivity, re-diversifying may improve long-term farm viability and stabilize US food production. However, diversifying may also reduce overall productivity. Over 16 years, we studied the relationship between rotation-wide productivity and stability against weather variation in the western Corn Belt. Rotations included the corn-soybean rotation and six, 4-year rotations containing 3-4 field crops each. We found that, although the corn-soybean rotation produced the most grain per acre, it was also the most at risk to weather extremes. This risk could be avoided at no cost to productivity: The corn-oat-winter wheat-soybean rotation produced as much grain as corn-soybean on average, while being as reliable as the most reliable rotations. Crop selection, sequencing, and duration of diversification were critical to these results. Beneficial rotation effects, such as favorable crop legacies, contributed to higher corn and soybean yields in diversified rotations and increased with time. Selecting crops that responded to different weather patterns lent stability, but these weather responses did not correspond to warm- vs cool-season or grass vs legume categories. Growers choose rotations based on complex factors, including policies that dictate viable management. By formulating policies to accommodate these findings, we expect growers will be able to implement rotations that improve the stability of their operations and US agricultural production while maintaining overall production of food, fuel, and fiber.
Technical Abstract: The crop rotation is a farm-scale management choice that dictates agronomic output, ecological impacts, and farm viability. Rotations have become less diverse recently. Re-diversifying may help agricultural systems meet the growing, dynamic demands from society and challenges from climate change. Using a long-term experiment, we tested whether diversified rotations could a) match the productivity (grain yield) of simplified rotations while b) stabilizing productivity against variable weather in the western Corn Belt. We identified rotation design choices that drive these productivity-stability dynamics. Although more productive rotations were more susceptible to weather (r = 0.63; p < 0.001), this tradeoff was surmountable (p < 0.001): the corn-oat-winter wheat-soybean (Zea mays L., Avena sativa L., Triticum aestivum L., Glycine max (L.) Merr.) rotation was a) no less productive than the highly unstable, corn-soybean rotation (p = 0.11); and b) only marginally less stable than the most stable rotation (p = 0.06). Crop selection and sequencing were critical to this outcome. High productivity was due to a) overyielding of individual crops in diversified rotations that increased with time; b) sequencing to allow higher-yielding winter crops; and c) beneficial crop legacy effects. Stability was highest in rotations that included crops belonging to more weather-niches (r2 = 0.67; p < 0.001). Surprisingly, these weather-niches did not correspond with traditional functional groups such as cool- vs warm-season crops. These results suggest four principles for the design, study, and implementation of diversified grain rotations that are stable under erratic weather and are as productive as current standard practices.