Evapotranspiration of Irrigated Crops under Warming and Elevated Atmospheric CO2: What Is the Direction of Change?

Fabio V. Scarpare,Claudio O. Stöckle,Mingliang Liu,Kirti Rajagopalan,Roger L. Nelson

doi:10.3390/atmos13020163

Fabio V. Scarpare, Claudio O. Stöckle + Show 3 more

Open Access

https://doi.org/10.3390/atmos13020163

Copy DOI

Journal: Atmosphere	Publication Date: Jan 20, 2022
Citations: 3	License type: CC BY 4.0

Affiliation: Washington State University

Abstract

Future changes in crop evapotranspiration (ETc) are of interest to water management stakeholders. However, long-term projections are complex and merit further investigation due to uncertainties in climate data, differential responses of crops to climate and elevated atmospheric CO2, and adaptive agricultural management. We conducted factor-control simulation experiments using the process-based CropSyst model and investigated the contribution of each of these factors. Five major irrigated crops in the Columbia Basin Project area of the USA Pacific Northwest were selected as a case study and fifteen general circulation models (GCM) under two representative concentration pathways (RCP) were used as the climate forcing. Results indicated a wide range in ETc change, depending on the time frame, crop type, planting dates, and CO2 assumptions. Under the 2090s RCP8.5 scenario, ETc changes were crop-specific: +14.3% (alfalfa), +8.1% (potato), −5.1% (dry bean), −8.1% (corn), and −12.5% (spring wheat). Future elevated CO2 concentrations decreased ETc for all crops while earlier planting increased ETc for all crops except spring wheat. Changes in reference ET (ETo) only partially explains changes in ETc because crop responses are an important modulating factor; therefore, caution must be exercised in interpreting ETo changes as a proxy for ETc changes.

Highlights

Understanding future changes in crop evapotranspiration and net irrigation requirements is important for irrigated agriculture around the globe [1,2,3]
While changes in atmospheric evaporative demand are determined by several meteorological variables, crop evapotranspiration (ETc), and net irrigation requirements (NIR) depend on additional factors
Our evaluation of many studies assessing future changes in ETc is that a great deal of confusion and misrepresentation exists due to methodologies that do not consider the multiple influences that future environmental conditions will have on crop water demand, on the main component, crop transpiration, and how different crop types will respond to changing conditions

Summary

Introduction

Understanding future changes in crop evapotranspiration and net irrigation requirements is important for irrigated agriculture around the globe [1,2,3]. While changes in atmospheric evaporative demand are determined by several meteorological variables (e.g., solar radiation, temperature, humidity, and wind speed), crop evapotranspiration (ETc), and net irrigation requirements (NIR) depend on additional factors. ETc depends on crop type, growing cycle length, canopy evolution, initial root zone soil moisture, root depth and distribution, and other factors. Our evaluation of many studies assessing future changes in ETc is that a great deal of confusion and misrepresentation exists due to methodologies that do not consider the multiple influences that future environmental conditions will have on crop water demand, on the main component, crop transpiration, and how different crop types will respond to changing conditions

Objectives

Methods

Results

Conclusion