Climate Change Impacts on Long-Term Field Experiments in Germany

CONTEXT Long-Term Field Experiments (LTEs) were implemented to study the long-term effects of different management practices, including tillage, fertilization and crop rotation under otherwise constant conditions. Climate change is expected to change these conditions, challenging interpretation of LTE data with regard to the distinction between climate change and management effects. OBJECTIVE The objective of the study was to quantify the expected, spatially differentiated changes of agroclimatic conditions for the German LTE sites as a precondition for modelling and LTE data interpretation. METHODS We developed a framework combining spatially distributed climate data and LTE metadata to identify the possible climatic changes at 247 LTE sites with experiments running for 20 years or more. The LTEs were classified using the following categories: fertilization, tillage, crop rotation, field crops or grassland, conventional or organic. We utilized climate variables (temperature, precipitation) and agroclimatic indicators (aridity, growing degree days, etc.) to compare a baseline (1971–2000) with future periods (2021−2100) under the IPCC's Shared Socio-economic Pathways (SSP). A comprehensive LTE risk assessment was conducted, based on changes in climate variables and agroclimatic indicators between baseline and future scenarios. RESULTS AND CONCLUSIONS Under the most extreme scenario (SSP585), 150 LTEs are expected to shift from humid and dry sub-humid to semi-arid conditions. Frost days in LTE areas are expected to decline by 81%, and the growing season to lengthen by up to 92%. The spatial differentiation of expected climate change also facilitates the identification of suitable sites for future agricultural practices and may inform the design of new LTEs. SIGNIFICANCE Our results may guide the interpretation of LTE data regarding the effect of climate change, facilitating future soil crop modelling studies with LTE data and providing information for planning new LTE sites to support future agricultural research and/or adapting management on existing LTE sites. The framework we developed can easily be transferred to LTE sites in agricultural regions worldwide to support LTE research on climate change impacts and adaptation.