Combined heat and drought suppress rainfed maize and soybean yields and modify irrigation benefits in the USA

Anna Scaini,Riccardo Bommarco,Giulia Vico,Xiangyu Luan

doi:10.1088/1748-9326/abfc76

Abstract

Heat and water stress can drastically reduce crop yields, particularly when they co-occur, but their combined effects and the mitigating potential of irrigation have not been simultaneously assessed at the regional scale. We quantified the combined effects of temperature and precipitation on county-level maize and soybean yields from irrigated and rainfed cropping in the USA in 1970–2010, and estimated the yield changes due to expected future changes in temperature and precipitation. We hypothesized that yield reductions would be induced jointly by water and heat stress during the growing season, caused by low total precipitation (P GS) and high mean temperatures (T GS) over the whole growing season, or by many consecutive dry days (CDD GS) and high mean temperature during such dry spells (T CDD) within the season. Whole growing season (T GS, P GS) and intra-seasonal climatic indices (T CDD, CDD GS) had comparable explanatory power. Rainfed maize and soybean yielded least under warm and dry conditions over the season, and with longer dry spells and higher dry spell temperature. Yields were lost faster by warming under dry conditions, and by lengthening dry spells under warm conditions. For whole season climatic indices, maize yield loss per degree increase in temperature was larger in wet compared with dry conditions, and the benefit of increased precipitation greater under cooler conditions. The reverse was true for soybean. An increase of 2 °C in T GS and no change in precipitation gave a predicted mean yield reduction across counties of 15.2% for maize and 27.6% for soybean. Irrigation alleviated both water and heat stresses, in maize even reverting the response to changes in temperature, but dependencies on temperature and precipitation remained. We provide carefully parameterized statistical models including interaction terms between temperature and precipitation to improve predictions of climate change effects on crop yield and context-dependent benefits of irrigation.

Highlights

The harvest we reap from our crop fields depend to large extent on the climatic conditions and their fluctuation (Porter and Semenov 2005)
We hypothesized that yield reductions would be induced jointly by water and heat stress during the growing season, caused by low total precipitation (PGS) and high mean temperatures (TGS) over the whole growing season, or by many consecutive dry days (CDDGS) and high mean temperature during such dry spells (TCDD) within the season
We considered two sets of climatic indices to capture different physiological mechanisms: (a) mean climatic conditions during the whole growing season, i.e. growing season precipitation total, precipitation over the growing season (PGS), and mean air temperature, TGS, and (b) shorter-term intra-seasonal conditions, as represented by maximum number of consecutive days with precipitation

Summary

Introduction

The harvest we reap from our crop fields depend to large extent on the climatic conditions and their fluctuation (Porter and Semenov 2005). Increased frequency of co-occurring high temperatures and low precipitation (Mazdiyasni and AghaKouchak 2015, Alizadeh et al 2020) suppresses crop yields by causing heat and water stress in the crop plants (Lesk et al 2016, Zscheischler et al 2017). Parameterized yield models that include interaction terms between temperature and precipitation hold potential to improve predictions of climate change impacts on crop yield (Carter et al 2018). Analyses of yields from arable fields with detailed climatic data show that interactive effects of precipitation and temperature or precipitation and vapor pressure deficit are needed to explain yield variation (Urban et al 2015, Carter et al 2018). The combined effects of heat and water stress on yields have often been overlooked in field-scale experiments and modeling (Rötter et al 2018)

Methods

Results

Discussion

Conclusion