Investigating the effects of inter-annual weather variation (1968–2016) on the functional response of cereal grain yield to applied nitrogen, using data from the Rothamsted Long-Term Experiments

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

doi:10.1016/j.agrformet.2019.107898

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

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https://doi.org/10.1016/j.agrformet.2019.107898

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Abstract

The effect of weather on inter-annual variation in the crop yield response to nitrogen (N) fertilizer for winter wheat (Triticum aestivvum L.) and spring barley (Hordeum vulgare L.) was investigated using yield data from the Broadbalk Wheat and Hoosfield Spring Barley long-term experiments at Rothamsted Research. Grain yields of crops from 1968 to 2016 were modelled as a function of N rates using a linear-plus-exponential (LEXP) function. The extent to which inter-annual variation in the parameters of these responses was explained by variations in weather (monthly summarized temperatures and rainfall), and by changes in the cultivar grown, was assessed.The inter-annual variability in rainfall and underlying temperature influenced the crop N response and hence grain yields in both crops. Asymptotic yields in wheat were particularly sensitive to mean temperature in November, April and May, and to total rainfall in October, February and June. In spring barley asymptotic yields were sensitive to mean temperature in February and June, and to total rainfall in April to July inclusive and September.The method presented here explores the separation of agronomic and environmental (weather) influences on crop yield over time. Fitting N response curves across multiple treatments can support an informative analysis of the influence of weather variation on the yield variability. Whilst there are issues of the confounding and collinearity of explanatory variables within such models, and that other factors also influence yields over time, our study confirms the considerable impact of weather variables at certain times of the year. This emphasizes the importance of including weather temporal variation when evaluating the impacts of climate change on crops.

Highlights

Many factors affect cereal crop yields including weather and climate, soil structure and fertility, pest, weed and disease incidence, previous cropping, cultivar, fertilizer applications and other agronomic practices
Nitrogen-yield response curves, individual years Yield response curves fitted with separate a, b and c parameters for each individual year (Fig. 3(b)), but with a common value of the nonlinear parameter, r, estimated at 0.988, explained more variability compared to a single common N response curve (Fig. 3(a)) fitted to all years (F(9.69, 138, 153), P < 0.001)
(3) Significant variability in N yield response curves was explained by inter-annual variation in weather at different times of the year and by cultivar in each crop

Summary

Introduction

Many factors affect cereal crop yields including weather and climate, soil structure and fertility, pest, weed and disease incidence, previous cropping, cultivar, fertilizer applications and other agronomic practices. It is predicted that to keep pace with rising food demand, global crop production will need to be 60% greater than current levels by 2050, with fewer inputs and no increase in agricultural land use (FAO, 2017) This intensification of crop production must accommodate adaptation to global change in climate: average global temperature in 2016 was 1.43°C above the 20th century average (NOAA, 2017); and warming is anticipated to continue throughout the remainder of this century, including more frequent high temperature extremes and more variable rainfall, due to anthropogenic emissions of greenhouse gases (IPCC, 2014). Variations in rainfall have long been associated with variations in the grain yield of wheat (Fisher, 1925; Lawes and Gilbert, 1871) and spring barley (Wishart and Mackenzie, 1930) These variations in rainfall may contribute to an increased frequency of drought conditions, reducing plant growth (da Silva and Kay, 1997). Whilst the crop response to drought develops over a comparatively long-time scale (Peña-Gallardo et al, 2019), even brief exposure to high temperature at sensitive stages of crop development, such as anthesis, can reduce wheat grain yield considerably, largely due to lower seed set (Ferris et al, 1998; Wheeler et al, 1996)

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