Abstract
Abstract. Crop yield is reduced by heat and water stress and even more when these conditions co-occur. Yet, compound effects of air temperature and water availability on crop heat stress are poorly quantified. Existing crop models, by relying at least partially on empirical functions, cannot account for the feedbacks of plant traits and response to heat and water stress on canopy temperature. We developed a fully mechanistic model, coupling crop energy and water balances, to determine canopy temperature as a function of plant traits, stochastic environmental conditions, and irrigation applications. While general, the model was parameterized for wheat. Canopy temperature largely followed air temperature under well-watered conditions. But, when soil water potential was more negative than −0.14 MPa, further reductions in soil water availability led to a rapid rise in canopy temperature – up to 10 ∘C warmer than air at soil water potential of −0.62 MPa. More intermittent precipitation led to higher canopy temperatures and longer periods of potentially damaging crop canopy temperatures. Irrigation applications aimed at keeping crops under well-watered conditions could reduce canopy temperature but in most cases were unable to maintain it below the threshold temperature for potential heat damage; the benefits of irrigation in terms of reduction of canopy temperature decreased as average air temperature increased. Hence, irrigation is only a partial solution to adapt to warmer and drier climates.
Highlights
High and stable crop yield requires suitable climatic conditions throughout the growing season
We developed a mechanistic model to estimate crop canopy temperature as a function of crop physiology, soil features, and climatic conditions, coupling the canopy energy balance and the water transport through the soil–plant–atmosphere continuum (SPAC), with stomatal conductance based on an optimality principle
To quantify the compound effects of air temperature and precipitation regimes on canopy temperature and the potential of irrigation to reduce the occurrence of crop heat stress, we developed a mechanistic model describing the coupled canopy energy and water balances and their interactions with the water balance of the rooting zone
Summary
High and stable crop yield requires suitable climatic conditions throughout the growing season. Like water scarcity and high temperatures, can adversely affect crop growth, development, and yield, as shown by controlled-condition and field experiments, large-scale surveys, and crop model applications (e.g., Zampieri et al, 2017; Daryanto et al, 2017; Kimball et al, 2016; Ray et al, 2015; Asseng et al, 2015) Both water and heat stress impair photosynthesis (Way and Yamori, 2014; Lawlor and Tezara, 2009), undermine crop growth (Hsiao, 1973; Hatfield and Prueger, 2015) and reproduction (Prasad et al, 2011), and hasten crop development and leaf senescence (Lobell et al, 2012), the physiological mechanisms can differ (Fahad et al, 2017).
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