Climate and management interaction cause diverse crop phenology trends

Abstract

Growing evidence suggests that the warming trend observed in many parts of the world has considerably modified crop phenology during the last decades but little is known about the impact of changes in crop management on crop phenology and possible interactions with temperature increase, and whether responses can be generalized across crop types. Here we evaluate the effects of climate and management on crop phenology by using observations for winter rapeseed and winter rye obtained in Germany for the period 1960–2013 by using piecewise linear regressions of temperature and phenology data on year. We show that long-term trends in crop phenology are crop-specific. The length of the vegetative phase of winter rapeseed declined by 4.8days per decade in the period 1979–2013. However, the corresponding decline for winter rye was only 1.3days per decade in the period 1978–2013 with the difference caused by change in management practices such as the introduction of early flowering cultivars of winter rapeseed or changes in sowing date of winter rapeseed and winter rye during the last decades in Germany. The length of the reproductive phase of winter rye declined by 0.9days per decade between 1976 and 2013 in response to the warming trend in that period. In contrast, the extended use of late maturing cultivars with a longer grain filling period and changed planting densities over-compensated for the effect of increasing temperature on the length of the reproductive phase of winter rapeseed and caused an increasing trend of 2.0days per decade between 1992 and 2013. The sowing date of winter rye advanced by 1.3days per decade in the period 1972–2013. The length of the phase between maturity and harvest increased considerably for both crops and compensated partly for the effect of increasing temperature to shorten the preceding phenological phases. We conclude that it is essential to account for interactions between climate and crop management in climate change impact analysis and assessment studies and that differences among crops need to be considered.