Field and model assessments of irrigated soybean responses to increased air temperature

Authors: SIMA, MATTHEW - Qingdao Agricultural University; FANG, QUANXIAO - Qingdao Agricultural University; Burkey, Kent; Ray, Sam; Pursley, Walter; KERSEBAUM, KURT - Leibniz Centre; BOOTE, KENNETH - University Of Florida; Malone, Robert - Rob

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2020
Publication Date: 9/28/2020
Citation: Sima, M., Fang, Q., Burkey, K.O., Ray, S.J., Pursley, W.A., Kersebaum, K., Boote, K., Malone, R.W. 2020. Field and model assessments of irrigated soybean responses to increased air temperature. Agronomy Journal. 112:4849-4860. https://doi.org/10.1002/agj2.20394.
DOI: https://doi.org/10.1002/agj2.20394

Interpretive Summary: Predicting climate change effects on crops is essential for assessing potential impacts on food supplies and developing mitigation strategies. This is possible through development of crop models validated by field experiments. In this study, a team of crop modelling experts from China, Germany, University of Florida, and two USDA-ARS locations (Fort Collins, CO and Ames, IA) tested soybean growth models for the effects of elevated temperature, and compared the results with elevated temperature field trials conducted by USDA-ARS scientists in Raleigh, NC. The CROPGRO and HERMES soybean models both predicted seed yield and biomass production losses similar to the observed effects of elevated temperature in field trials, although the HEREMES model underestimated crop maturity date. Both models were used in conjunction with general circulation models to predict climate change effects on soybean production in the year 2100. Elevated temperature was predicted to reduce both soybean biomass and seed yield. The inhibitory effects of rising temperature were mitigated by elevated CO2 and water stress with the magnitude of mitigation dependent upon the level of CO2 in the atmosphere and the selected rainfed/irrigation management practice.

Technical Abstract: The ability to correctly project climate change effects on crop yield through field experiments and crop modeling is essential for developing mitigation strategies. The objective of this study was to compare two different soybean (Glycine max L. Merrill) models (CROPGRO and HERMES) within the Root Zone Water Quality Model (RZWQM) for their ability to predict climate change effects on soybean. The models were calibrated for measured temperature responses using data from a three-year air exclusion experiment (2015-2017). The average 2.9 degrees C increase in air temperature during three soybean growing seasons decreased observed seed yield by 27% and final biomass by 18%, but did not significantly affect soybean maturity date. HERMES simulated greater reductions in soybean yield (24.6 vs. 12.0%) and biomass (26.3 vs. 6.8%) and showed better response to temperature increase than CROPGRO. However, HERMES simulated maturity dates were about eight days earlier than observed, indicating that an improvement was needed in the model for soybean phenology response to temperature increase. Both calibrated models were then used to predict soybean production by the end of 2100 using 40 general circulation models (GCMs) and two Representative Concentration Pathways (RCP4.5 and RCP8.5) under both rainfed and irrigated conditions. Both crop models simulated similar climate change effects in terms of yield and biomass, compared with the baseline simulations. For both models, much greater reductions in biomass and seed yield were simulated for RCP8.5 than for RCP4.5 due to higher temperature, which could be mitigated or offset by elevated CO2 for both Pathways. In addition, both models predicted lower variability of biomass and seed yield across these GCMs under irrigated than under rainfed conditions. CROPGRO predicted a greater positive climate change effect in response to the projected higher precipitation and increased CO2 (compared with baseline conditions) than HERMES. Soybean production in the region will likely benefit more from the projected higher precipitation and elevated CO2 under rainfed conditions than under irrigated conditions.