The impact of weather and increased atmospheric CO2 from 1892 to 2016 on simulated yields of UK wheat.

John W G Addy,Richard H Ellis,Andy J Macdonald,Andrew Mead,Mikhail A Semenov

doi:10.1098/rsif.2021.0250

John W G Addy, Richard H Ellis + Show 3 more

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https://doi.org/10.1098/rsif.2021.0250

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Abstract

Climate change effects on UK winter wheat grain yield are complex: warmer temperature, negative; greater carbon dioxide (CO2) concentration, positive; but other environmental variables and their timing also affect yield. In the absence of long-term experiments where temperature and CO2 concentration were manipulated separately, we applied the crop simulation model Sirius with long-term daily meteorological data (1892–2016) for Rothamsted, Hertfordshire, UK (2007–2016 mean growing season temperature 1.03°C warmer than 1892–1991), and CO2 concentration over this period, to investigate the separate effects of historic CO2 and weather on simulated grain yield in three wheat cultivars of the modern era. We show a slight decline in simulated yield over the period 1892–2016 from the effect of weather (daily temperature, rainfall and sunshine hours) at fixed CO2 (294.50 ppm, 1892 reference value), but a maximum 9.4% increase when accounting for increasing atmospheric CO2 (from 294.50 to 404.21 ppm), differing slightly among cultivars. Notwithstanding considerable inter-annual variation, the slight yield decline at 294.50 ppm CO2 over this 125-year period from the historic weather simulations for Rothamsted agrees with the expected decline from temperature increase alone, but the positive yield trend with actual CO2 values does not match the recent stagnation in UK wheat yield.

Highlights

Temperature and carbon dioxide (CO2) atmospheric concentration have both increased on average annually from 1892 to 2016 [1]
Some care is needed in interpreting these trends with the year, since the differences between years include the impact of the complex variability of weather factors, resulting in the considerable inter-annual variation in simulated yields which dominates these slight trends
In contrast with investigations in modified UK field environments with irrigation, in which warmer temperatures reduced both crop duration and yield and greater CO2: Avalon (CO2) increased yield [2], this simulation study for Rothamsted, UK, in which rainfall varied according to that recorded at the site for each year, indicated reduced crop duration with warmer temperature but only a marginal reduction in yield alongside considerable inter-annual variation

Summary

Introduction

Temperature and carbon dioxide (CO2) atmospheric concentration have both increased on average annually from 1892 to 2016 [1]. In spite of continued variety improvement, wheat (Triticum aestivum L.) grain yields have stagnated since the mid-1990s in Europe [4] and the UK, with a mean value of 7.84 t ha−1 on UK farms for the period 1996–2017 [5], though with considerable inter-annual variation, following a substantial increase in annual yields over the previous 40 years [6]. Wheat yield on the Broadbalk long-term experiment at Rothamsted, Hertfordshire, UK, has remained relatively constant over this period on those plots receiving commercially relevant fertilizer applications [8] with no change in agronomy other than variety These yield plateaus have occurred despite the continuing rise in atmospheric CO2 royalsocietypublishing.org/journal/rsif J.

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