Preprints
https://doi.org/10.5194/esd-2021-24
https://doi.org/10.5194/esd-2021-24

  22 Apr 2021

22 Apr 2021

Review status: this preprint is currently under review for the journal ESD.

Impacts of hot-dry compound extremes on US soybean yields

Raed Hamed1, Anne F. Van Loon1, Jeroen Aerts1,2, and Dim Coumou1,3 Raed Hamed et al.
  • 1Department of Water and Climate Risk, Institute for Environmental Studies (IVM), Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
  • 2Deltares Institute, Delft, The Netherlands
  • 3Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands

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 explore synergistic effects between drivers that can lead to severe impacts. The study combines weather data from reanalysis, satellite-based evapotranspiration and root-zone soil moisture with sub-national crop yields using statistical methods that account for interaction effects. Our model can explain on average about half of the year-to-year yield variability (60 % on all years and 40 % on 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 less so during wet conditions. Compound and interacting hot and dry August conditions (defined by the 95th and 5th percentiles of temperature and soil moisture, respectively) reduce yields by 1.25 standard deviation. This sensitivity is, respectively, 6 and 3 times larger than the sensitivity to hot or dry conditions alone. Other important drivers of negative yield responses are lower evapotranspiration early in the season and lower minimum temperature late in the season, both likely reflecting an increased risk of frost. The sensitivity to the identified drivers varies across the spatial domain with higher latitudes, and thus colder regions, being less sensitive to hot-dry August months. Historic trends in identified drivers indicates that US soybean has generally benefited from recent shifts in weather. Overall warming conditions have reduced the risk of frost in early and late-season and potentially allowed for earlier sowing dates. More importantly, summers have been getting cooler and wetter over eastern US. Still, despite these positive changes, we show that the frequency of compound hot-dry August month has remained unchanged over 1946–2016. Moreover, in the longer term, climate models project substantially warmer summers for the continental US which likely creates risks for soybean production.

Raed Hamed et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2021-24', Corey Lesk, 20 May 2021
  • RC2: 'Comment on esd-2021-24', Anonymous Referee #2, 13 Jun 2021

Raed Hamed et al.

Raed Hamed et al.

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Short summary
Soy yields in the US are affected by climate variability. We look at the most impactful climate drivers to highlight the relation between compound events and agricultural impacts. Our statistical model, which accounts for interaction effects, shows that soy yields are most negatively influenced by the combination of high temperature and low soil moisture during the summer crop reproductive period. Early season evapotranspiration and late season low temperature also contribute to reduced yields.
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