Simulating impacts of climate change on cotton yield and water requirement using RZWQM2

Authors: CHEN, XIAOPING - Chinese Academy Of Sciences; QI, ZHIMING - McGill University - Canada; GUI, DONGWEI - Chinese Academy Of Sciences; GU, ZHE - Chinese Academy Of Sciences; Ma, Liwang; ZENG, FANJIANG - Chinese Academy Of Sciences; LI, LANHAI - Chinese Academy Of Sciences

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2019
Publication Date: 5/30/2019
Citation: Chen, X., Qi, Z., Gui, D., Gu, Z., Ma, L., Zeng, F., Li, L. 2019. Simulating impacts of climate change on cotton yield and water requirement using RZWQM2. Agricultural Water Management. 222:231-241. https://doi.org/10.1016/j.agwat.2019.05.030.
DOI: https://doi.org/10.1016/j.agwat.2019.05.030

Interpretive Summary: Understanding the potential impacts of climate change on cotton yield and water demand in the semi-arid region of northwestern China is crucial in allocating water resources and adopting alternative cropping systems. In this study, cotton yield and water requirement under future climate scenarios were evaluated for a desert oasis. Six general circulation models (GCMs), under moderate and high representative concentration pathway (RCP) scenarios (RCP4.5 and RCP8.5) and elevated CO2 concentration, were used to project climate for near (2041-2060) and far future (2061-2080) periods. The impacts of climate change on cotton yield and water requirement were then simulated using the Root Zone Water Quality Model (RZWQM2), which was calibrated with experimental data from 2007 to 2014. For the study region, the GCMs predicted an increase of 4.28 °F and 5.83 °F in temperature and of 0.047 in and 0.059 in in precipitation during growing seasons (April-October) for 2041-2060 and 2061-2080, respectively. For 2041-2060, seed cotton yield was projected to increase by 0.11 tons/ac (5.6%) under RCP4.5 and 0.09 tons/ac (4.5%) under RCP8.5 comparing to the baseline yield of 1.89 tons/ac; however, for 2061-2080, the model predicted a 0.14 tons/ac (7.6%) yield increase under RCP4.5 but a 0.13 tons/ac (6.5%) decrease under RCP8.5. The increased cotton yield was attributable to the fertilization effect of enhanced CO2 that offset the adverse effects of shorter growing seasons (8.0-9.5 days). Averaged across the RCP4.5 and RCP8.5, simulated cropping season water requirement for the 2041-2060 and 2061-2080 were 28.67 in and 27.87 in, respectively, decreases by 7.5% and 10.3% relative to the present day baseline (30.95 in), respectively., which was attributed to shorter growing seasons and enhanced CO2 effects on stomatal resistance. These results suggest that the region’s water crisis may be alleviated in the future.

Technical Abstract: Assessing the potential impacts of climate change on cotton (Gossypium hirsutum L.) yield and water demand is crucial in allocating water resources. In this study, cotton yield and water requirement under future climate scenarios were evaluated for a desert oasis. Six general circulation models (GCMs), under moderate and high representative concentration pathway (RCP) scenarios (RCP4.5 and RCP8.5) and elevated CO2 concentration, were used to project climate for near (2041-2060) and far future (2061-2080) periods. With current management practices, the impacts of climate change on cotton yield and water requirement were simulated using the Root Zone Water Quality Model (RZWQM2), which was calibrated with experimental data from 2007 to 2014 in a previous study. For the study region, the climate models predicted an increase of 2.38°C and 3.24°C in temperature and of 1.2 mm and 1.5 mm in precipitation during growing seasons (April-October) for 2041-2060 and 2061-2080, respectively. For 2041-2060, seed cotton yield was projected to increase by 0.24 Mg/ha (5.6%) under RCP4.5 and 0.19 Mg/ha (4.5%) under RCP8.5 comparing to the baseline yield of 4.23 Mg/ha; however, for 2061-2080, the model predicted a 0.32 Mg/ha (7.6%) yield increase under RCP4.5 but a 0.28 Mg/ha (6.5%) decrease under RCP8.5. The increased cotton yield was attributable to the fertilization effect of enhanced CO2 dominating the detrimental effects of shorter growing seasons (8.0-9.5 days). Alleviated low temperature stress also slightly promoted cotton yield. Averaged across the RCP4.5 and RCP8.5, simulated cropping season water requirement for the 2041-2060 and 2061-2080 were 728 mm and 706 mm, respectively, decreases by 7.5% and 10.3% relative to the present day baseline (786 mm), respectively, which was attributed to shorter growing seasons and enhanced CO2 effects on stomatal resistance. These projections suggest that the region’s water crisis may be alleviated in the future.