Impacts of compound hot–dry extremes on US soybean yields

Abstract

Abstract. The US agriculture system supplies more than one-third of globally traded soybean, and with 90 % of US soybean produced under rainfed agriculture, soybean trade is particularly sensitive to weather and climate variability. Average growing season climate conditions can explain about one-third of US soybean yield variability. Additionally, crops can be sensitive to specific short-term weather extremes, occurring in isolation or compounding at key moments throughout crop development. Here, we identify the dominant within-season climate drivers that can explain soybean yield variability in the US, and we explore the synergistic effects between drivers that can lead to severe impacts. The study combines weather data from reanalysis and satellite-informed root zone soil moisture fields with subnational crop yields using statistical methods that account for interaction effects. On average, our models can explain about two-thirds of the year-to-year yield variability (70 % for all years and 60 % for out-of-sample predictions). The largest negative influence on soybean yields is driven by high temperature and low soil moisture during the summer crop reproductive period. Moreover, due to synergistic effects, heat is considerably more damaging to soybean crops during dry conditions and is less problematic during wet conditions. Compounding and interacting hot and dry (hot–dry) summer conditions (defined by the 95th and 5th percentiles of temperature and soil moisture respectively) reduce yields by 2 standard deviations. This sensitivity is 4 and 3 times larger than the sensitivity to hot or dry conditions alone respectively. Other relevant drivers of negative yield responses are lower temperatures early and late in the season, excessive precipitation in the early season, and dry conditions in the late season. We note that the sensitivity to the identified drivers varies across the spatial domain. Higher latitudes, and thus colder regions, are positively affected by high temperatures during the summer period. On the other hand, warmer southeastern regions are positively affected by low temperatures during the late season. Historic trends in identified drivers indicate that US soybean production has generally benefited from recent shifts in weather except for increasing rainfall in the early season. Overall, warming conditions have reduced the risk of frost in the early and late seasons and have potentially allowed for earlier sowing dates. More importantly, summers have been getting cooler and wetter over the eastern US. Nevertheless, despite these positive changes, we show that the frequency of compound hot–dry summer events has remained unchanged over the 1946–2016 period. In the longer term, climate models project substantially warmer summers for the continental US, although uncertainty remains as to whether this will be accompanied by drier conditions. This highlights a critical element to explore in future studies focused on US agricultural production risk under climate change.

Increased probability of hot and dry weather extremes during the growing season threatens global crop yields

“…3 E,F)—all highly important regions for global soybean production. Noteworthy, for North America, also previous research has reported yield reductions during compound hot-dry events 43 .…”

Persistent La Niña’s favor joint soybean harvest failures in North and South America

“…We find that summer soil moisture is strongly preconditioned by antecedent soil moisture in the SESA and US regions. Soil moisture memory can persist over several months which implies that spring anomalies can influence summer soil moisture conditions and in turn intensify summer land-atmosphere feedbacks (Anderson et al, 2017a;Hamed et al, 2021;Sippel et al, 2018;Sippela et al, 2016). The lack of a significant relationship between antecedent (spring) and summer soil moisture in the CB region could be related to local land-atmosphere feedbacks, which can force an inverse relationship between austral spring and summer moisture conditions particularly during ENSO events (Grimm et al, 2007).…”

“…1a). Wisconsin, Michigan, Minnesota and North and South Dakota are omitted from the US cluster as these northern states were previously shown to have a different seasonal climate sensitivity compared to the rest of the US regions considered (Hamed et al, 2021;Schauberger et al, 2017). Weighted spatial average timeseries are calculated at regional level for the three defined regions https://doi.org/10.5194/egusphere-2022-960 Preprint.…”

“…Soybean harvest failures are often related to anomalously hot and dry conditions in summer (Hamed et al;. Studies have shown that inter-annual climate variability is one key factor that strongly impacts crop yields (Lobell et al, 2011;Lobell and Field, 2007;Ray et al, 2015).…”

Coordinated evaporative demand and precipitation maximize rainfed maize and soybean crop yields in the USA

“…Temperature, precipitation and their interaction are often used to predict crop yields with statistical models (e.g., Lobell & Field, 2007; Luan et al, 2021; Matiu et al, 2017; Ray et al, 2015), explaining approximately a third of crop yield variability globally, with large local variations (Ray et al, 2015). Several aspects of the crop response to precipitation and temperature are mediated by soil water availability (e.g., Hamed et al, 2021; Luan & Vico, 2021; Riha et al, 1996), making soil moisture a better predictor of yields (Proctor et al, 2022). Soil moisture data are unavailable for long periods and over wide geographical areas, limiting robust statistical inference.…”