This LTE overview map contains information about 500 agricultural experiments with a duration of at least 20 years. You can narrow down your selection by different research themes (e.g. fertilization or tillage), duration times, land use, farming category, and status, identify the location of the trial, get information of the responsible parties and LTE literature or download metadata. The following networks are included: EJP SOIL (European Joint Programme), GLTEN (Global long-term experiment network), ILTER (International long-term ecological research), IOSDV (International Organic Nitrogen Fertilization Experiment), NLFT (National Long-term Fertilization Trials, Hungary), RetiBio 2 (Italy).
(You can get easy access to your LTE of interest by using the categories as a filter criteria.)
 "Metadata of agricultural long-term experiments in Europe exclusive of Germany" https://doi.org/10.1016/j.dib.2021.107322
 "Long-term field experiments in Germany: classification and spatial representation" https://doi.org/10.5194/soil-6-579-2020
 "Provision of Metadata of European Agricultural Long-Term Experiments through BonaRes and EJP SOIL Collaboration" BonaRes. Repos., v1 (2022) https://doi.org/10.20387/bonares-40kc-2661
 "Agricultural long-term experiments in Europe outside Germany", Bona Res. Repos., v1 (2021) https://doi.org/10.20387/bonares-eff3-0mb4
 "Long-term Field Experiments in Germany", Bona Res. Repos., v1 (2019) https://doi.org/10.20387/BonaRes-3TR6-MG8R