The Effects of Changing Environments, Abiotic Stresses, and Management Practices on Cropland Evapotranspiration: A Review

The significance of crop evapotranspiration (ET_a) to climate science, agronomic research, and water resources is not in dispute. What continues to draw attention is how variability in ET_a is driven by changing environments, abiotic stresses, and management practices. Here, the impacts of elevated CO₂ concentration (e[CO₂]), elevated ozone concentration (e[O₃]), warming, abiotic stresses (water, salinity, heat stresses), and management practices (planting density, irrigation methods, mulching, nitrogen application) on cropland ET_a were reviewed, along with their possible causes and estimation. Water and salinity stresses, e[O₃], and drip irrigation adoption generally led to lower total growing–season ET_a. However, total growing–season ET_a responses to e[CO₂], warming, heat stress, mulching, planting density, and nitrogen supplement appear inconsistent across empirical studies. The effects of e[CO₂], e[O₃], water and salinity stresses on total growing–season ET_a are attributed to their influence on stomatal conductance, root water uptake, root and leaf area development, microclimate, and potentially phenology. Total growing–season ET_a in response to warming is affected by variations in ambient growing–season mean air temperature and phenology. The differences in crop ET_a under varying planting densities are due to their differences in leaf area. The responses of ET_a to heat stress, mulching, and nitrogen application represent trade–off between their opposite effects on transpiration and evaporation, along with possibly phenology. Modified ET_a models currently in use can estimate the response of ET_a to the many aforementioned factors except for e[O₃], heat stress, and nitrogen application. These factors offer a blueprint for future research inquiries.