Does agroecosystem management mitigate historic climate impacts on dryland winter wheat yields?

Authors: Miner, Grace; Stewart, Catherine; Vigil, Merle; Poss, David; HALEY, SCOTT - Colorado State University; JONES-DIAMOND, SALLY - Colorado State University; MASON, ESTEN - Colorado State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2022
Publication Date: 9/2/2022
Citation: Miner, G.S., Stewart, C.E., Vigil, M.F., Poss, D.J., Haley, S.D., Jones-Diamond, S.M., Mason, E.R. 2022. Does agroecosystem management mitigate historic climate impacts on dryland winter wheat yields? Agronomy Journal. 114(6):3515-3530. https://doi.org/10.1002/agj2.21198.
DOI: https://doi.org/10.1002/agj2.21198

Interpretive Summary: Dryland agroecosystems are already operating at the extremes of precipitation and temperature. Identifying future regional climate adaptation strategies requires that local historical climate impacts on crop yields are accessible and interpretable to farmers and critical stakeholders. A team of USDA and university scientists leveraged two long-term wheat yield datasets to identify how precipitation and temperature have historically impacted winter wheat yields in eastern Colorado, and to investigate how management practices like tillage and fallowing may moderate climate impacts. They also investigated whether high-yielding wheat varieties are less able to withstand water or high temperature stress than low-yielding varieties. Their results indicate that spring and summer temperatures in this agroecosystem are already at or above optimum, suggesting that climate-associated yield impacts in these systems will be rapid. No-till management offers yield benefits through differences in soil water at planting but does not result in significant additional in-season water capture or storage over conventional tillage. They found no evidence for a trade-off between wheat grain yield and water or heat stress tolerance, and the high frequency of water and heat stress in these systems has likely already led to selection for these traits in traditional wheat breeding programs. Maintaining wheat yields in these dryland systems under climate pressures will likely require producers to balance yield goals with maintaining adequate soil water and soil cover, underscoring the difficulty of identifying win-win climate adaptations.

Technical Abstract: Global and national studies that quantify climate effects on crop yields are invaluable for assessing generalized impacts on global food supplies, yet do not contain the spatial resolution necessary to identify local mediating impacts of agroecosystem management. Our objectives were to identify (i) what climate factors have historically impacted winter wheat (Triticum aestivum L.) yields in eastern Colorado, (ii) how management practices may mitigate climate impacts on yields, and (iii) probe the potential for varietal selection to climate extremes. We paired long-term grain yield data (1993 – 2015) for wheat in rotations that varied in management (e.g., no-till, conventional tillage, with and without fallow) with robust on-site weather data. We also utilized data from co-located variety trials to investigate trade-offs between mean yields and the ability to withstand water/temperature stress. We found that precipitation in the ~ 90-day window after green-up was nearly as predictive of yields as total growing season precipitation. While precipitation and air temperatures are tightly linked in this agroecosystem, temperatures were more predictive of yields.