Grain legume yield instability has increased over 60 years in long-term field experiments as measured by a scale-adjusted coefficient of variation

Grain legumes produce high quality protein for food and feed, and provide ecosystem services contributing to sustainable cropping systems. Yet yield instability is perceived to be high, resulting in low adoption by farmers in Europe, where grain legumes were cultivated on only 1.5% of the arable land in 2014. The objective of this study was to assess whether grain legume yield instability has changed over time between 1953 and 2015. We used data from two long-term field experiments in Europe and accounted for yield differences between crops by applying Taylor’s Power Law (TPL) in a scale-adjusted coefficient of variation (aCV). The results showed that grain legume yield instability was higher than that of autumn-sown cereals, but similar to those of broad-leaved crops and spring-sown cereals. Temporal yield instability of all crops significantly increased over time by more than half from 1960 to 2015 in Borgeby (Sweden) and from 1953 to 2008 in Berlin-Dahlem (Germany). This happened despite progress in plant breeding and technical development in agronomy, and climate change may be an important driver. Our findings contribute to improving the perception of grain legumes in general and point towards necessary improvements to support adaption to climate change.