Simulated deficit irrigation and climate change effects on sunflower production in Eastern Colorado with CSM-CROPGRO-Sunflower in RZWQM2

Authors: ZHANG, JING - Northwest A&f University; Zhang, Huihui; SIMA, MATHEW - Princeton University; Trout, Thomas; Malone, Robert - Rob; WANG, LI - Northwest A&f University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2020
Publication Date: 12/16/2020
Citation: Zhang, J., Zhang, H., Sima, M.W., Trout, T.J., Malone, R.W., Wang, L. 2020. Simulated deficit irrigation and climate change effects on sunflower production in Eastern Colorado with CSM-CROPGRO-Sunflower in RZWQM2. Agricultural Water Management. 246. Article e106672. https://doi.org/10.1016/j.agwat.2020.106672.
DOI: https://doi.org/10.1016/j.agwat.2020.106672

Interpretive Summary: Sunflower (Helianthus annuus L.) has been used as an alternative summer crop in the traditional wheat (Triticum aestivum L.) -fallow rotation in the Great Plains of the USA. However, few studies have been conducted to quantify sunflower productivity and water productivity (WP) under semi-arid conditions and projected climate change. Experiments were conducted in 2008, 2010, and 2011 for sunflower under deficit irrigation conditions that met portions of potential crop evapotranspiration (ETc) in eastern Colorado. The field data were used to calibrate and validate the CSM-CROPGRO-Sunflower model that is incorporated in Root Zone Water Quality Model (RZWQM2). The model was then used to simulate sunflower production under forecasted climate conditions under four Representative Concentration Pathways (RCP) scenarios (2.6, 4.5, 6.0, and 8.5) in the late 21st century (2080s) in Colorado. The results show that the model was able to adequately simulate sunflower biomass, yield, ETc, and soil water storage (SWS) under the different irrigation treatments in all three years. Under future climate change conditions, the model simulated greater impact of irrigation treatments than RCPs scenarios on sunflower production. The CO2 fertilization effect was not significant on sunflower yield, biomass, transpiration, WP and irrigation amount. Simulation results also showed that scheduling irrigations based on 60% of ETc was the best choice for sunflower in eastern Colorado. Climate change did not have an impact on sunflower biomass, yield, and WP.

Technical Abstract: Sunflower (Helianthus annuus L.) has been used as an alternative summer crop in the traditional wheat (Triticum aestivum L.) -fallow rotation in the Great Plains of the USA. However, few studies have been conducted to quantify sunflower productivity and water productivity (WP) under semi-arid conditions and projected climate change. Experiments were conducted in 2008, 2010, and 2011 on sunflowers under deficit irrigation to meet a fraction of crop evapotranspiration (ETc) as estimated by FAO-56 in eastern Colorado. The field data was used to calibrate and validate the CSM-CROPGRO-Sunflower model that is incorporated in the Root Zone Water Quality Model (RZWQM2). The calibrated model was then used to simulate sunflower production under projected climate conditions with four Representative Concentration Pathways (RCP) scenarios (2.6, 4.5, 6.0, and 8.5) in the late 21st century. The results showed that the model was able to adequately simulate sunflower biomass, yield, and soil water storage under the different irrigation treatments in all three years. The corresponding relative root mean square deviation (RRMSD) values were between 0.05-0.15 for the simulations of soil water storage, yield, and biomass. Under future climate change conditions, the model simulated greater impact of irrigation treatments than RCP scenarios on sunflower production. For example, yield was 3251.3, 2638.85 and 1937.17 kg ha-1 with 100%, 60 and 40% ETc irrigation under baseline (1992-2013) and was 2932.47, 2360.53 and 1810.65 with these irrigation treatments under RCP8.5 (2070-2091). Simulation results also showed that scheduling irrigations based on 60% of ETc was the best choice for sunflower WP in eastern Colorado. Climate change did not affect sunflower biomass, yield, and WP. An increasing trend of irrigation amount was simulated from the baseline to RCP8.5 scenario to maintain a certain percent of ETc due to high temperature projected. For instance, the irrigation amount for 100%, 60% and 40% of ETc irrigation treatment was 16.4%, 17.3%, and 20.0% higher, respectively, under RCP8.5 than those under baseline conditions with CO2 fertilization. Finally, our results demonstrated that RZWQM2 can be used to effectively schedule sunflower irrigations based on crop evapotranspiration requirement.