Does agroecosystem management mitigate historic climate impacts on dryland winter wheat yields?. (18th November 2022) - Miner, Grace L.
Abstract: Global studies that quantify climate effects on crop yields using top‐down spatial frameworks are invaluable for assessing generalized effects on world food supplies, yet do not contain the resolution necessary to identify local mediating effects of management. Our objectives were to identify (a) what climate factors have historically affected winter wheat ( Triticum aestivum L.) yields in eastern Colorado, (b) how management may mitigate climate impacts, and (c) the potential for varietal selection to climate extremes. We paired long‐term yield data for wheat in rotations that varied in management (tillage intensity, with and without fallow) with robust on‐site weather data. We also used data from colocated variety trials to investigate trade‐offs between mean yields and the ability to withstand water and temperature stress. Precipitation in April–June was nearly as predictive of yields as full growing season precipitation. While precipitation and air temperatures are tightly linked in this agroecosystem, temperatures were more predictive of yields than precipitation. Increases in minimum May temperatures positively affected yields, likely because of minimizing freeze damage, but did not offset detrimental effects of warmer daytime spring and summer temperatures. The largest negative temperature effects were caused by extreme maximum temperatures in June. No‐till with fallow maximized yields. Low‐ and high‐yielding varieties did not differ in yield responses to high temperatures, suggesting that future advancements in heat stress resistance will not necessarily require yield trade‐offs. Climate pressures will likely require producers to balance yield goals with maintaining soil cover, underscoring the difficulty of identifying win–win climate adaptations. Core Ideas: Precipitation in a 90‐d window (April–June) was nearly as predictive of yields as full growing season precipitation. Information on monthly air temperatures (April–June) was more predictive of wheat grain yields than precipitation. Daytime temperatures in May and June are already above optimum in most years, negatively affecting grain yields. Both no‐till and fallow increased the intercept of the yield response to precipitation and temperature. The slope of the yield responses to high temperatures did not differ between low‐ and high‐yielding varieties.