Warm nights during different periods of crop cycle reduce yield and its numerical and physiological components in wheat and barley: from field studies to modeling

GUILLERMO A. GARCIA; NEIL HURTH; ROMÁN A. SERRAGO; VÍCTOR GIMENEZ; DANIEL J. MIRALLES; IGNACIO ALZUETA; M. FERNANDA DRECCER

Saskatoon

Congreso; 1st International Wheat Congress; 2019

University of Saskatchewan

Climate change representsa continuous challengefor agriculture and world food security. A well-known characteristic of climate change is global warming, and the current knowledge on climate change highlightsthat temperature will be the most affected andpredictable variable. Global temperatureis projected to rise under most of the predicted emission scenarios between 1 and 3.7 °C to the end ofthis century. Literature showed from multi-model ensembles higher increases in the frequency of warm nightscompared to warm days and thereby asymmetric warming acrossthe day is expected to continue in the future.In this context, increases in temperature, and specially night temperatures, will affect most of the crops, but specially winter crops which, according to the predictions of IPCC, will be the most penalized in terms of yield and probably in terms of quality. However, most of the studies that try to predict the effects of climate change on crops (and especially temperature) were carried under controlled condition and/or by simulation models and few were carried under field conditions. The objectives of this study were (i) to investigatethe impact of high night temperatures during different period of crop cycle (i.e. critical period and grain filling) on grain yield (and its physiological and numerical components) in wheat andbarleyby using heating chambers placed on the crop growing in the field at19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering(critical period) and from 10 days post anthesis to physiological maturity (Grain filling) and (ii) to quantify and compare the impact of increasednight temperature on wheat and barley crops for different representative sites of the Argentinean Pampas by modeling using the Agricultural Production SystemssIMulator v 7.7 (APSIM) by historical climatic series. Results showed that night temperature increasesin the field during the critical period (ca.4°C in both crops and growing seasons)reduced yield in both wheat and barley (ca. 7% °C-1), due to reductions in grain number per unit area (ca. 6% °C-1), associated with a lower number of spikes per m2. Warmer night temperaturesaccelerated development reducing solar radiation capture with negative consequences forbiomass production without changes in Harvest index. Warmer night during grain filling reduced thousand grain weight ca. 3% °C-1causing grain yieldreductions of ca. 4% °C-1in both species. Modelling showed that wheat and barley yields declined across thePampas between ca. 2% and 9% per °C increase in the minimum temperature during the critical period, linked tolower cumulative radiation capture as a result of a shorter crop phase and lower incident radiation due todisplacement towards winter.