ADAPTATION STRATEGIES TO HIGH NIGHT TEMPERATURE IN WINTER CEREALES AND INTERACTION WITH MANAGEMENT PRACTICES

DANIEL JULIO MIRALLES; GARCIA G; SERRAGO RA; GIMENEZ V; DRECCER, M. FERNANDA

Sevilla

Congreso; XVI European Society for Agronomy Congress; 2020

Climate change represents one the most important challenges for agriculture around the world. A rising mean temperature is the weather variable consistently predicted by a range of different climate models for the 21st century. In some countries, a distinctive characteristic of this phenomenon is an asymmetric temperature increase, retrospective climate analyses demonstrated that minimum temperature (i.e. night temperature) has increased at a faster rate than maximum temperature (i.e. day temperature). The Argentinean Pampas, one of the most important agricultural areas in the world, has experienced such trend in the winter crop season (wheat and barley). To understand and quantify the impact of high night temperatures in wheat and barley a series of different field experiments using heated chambers placed on the crop between 7PM to 7AM during different stages of the crop cycle were combined with different planting densities, nitrogen and water availability. This approach was extended by using the Agricultural Production Systems sIMulator v 7.7 (APSIM) to quantify and compare the impact of increased night temperature (NTI) in wheat and barley on the Argentinean Pampas in a historical climate series. Field experiments showed that NTI accelerated crop development reducing solar radiation capture and negatively affecting biomass production without changes in harvest index. Night temperature increases reduced yield in both wheat and barley at a rate of ca. 7% °C-1 and 4% °C-1, when warming was applied during pre-and post-flowering, respectively. When NTI applied during the pre-flowering phase were combined with different fertilizer nitrogen rates and densities, the results showed that yield was penalized only at high nitrogen rates (ca. 7% °C-1). In the same way, warmer nights increased tiller mortality only under high nitrogen availability, reducing the final number of spikes established at flowering. Warmer nights reduced grain yield similarly across plant densities. Modelling showed that wheat and barley yields declined across the Pampas between ca. 2% and 9% °C-1 during the critical period, depending on the location. In summary, field experiments and modelling showed that NTI accelerated the crop development, reducing the cumulated intercepted radiation and thereby grain number and/or grain weight. Increases in resources availability (water and nutrients) and some management practices as plant density did nor reduce the negative effects of warmer nights. Changes in sowing date and flowering time seems to be the most suitable management practice to counterbalance the negative effects of warmer nights.