Crop yields and NPK use efficiency of a long-term experiment on a former sea bottom in the Netherlands

In the twentieth century, the ‘Zuyderzee’, an inland sea in the Netherlands, was closed off from the North Sea, and several ‘IJsselmeerpolders’ were created on the former sea bottom. In 1968, the Wageningen University decided to start an experimental farm in Oostelijk Flevoland, the Southeastern polder. The farm received the name ‘Ir. A.P. Minderhoudhoeve’ (APM). Although it was already known that the soils were very fertile, farmers and (soil) scientists lacked a sound scientific assessment of the time span with that high soil fertility status and ample soil reserves of P and K. Hence, the Soil Fertility group of the university designed a long-term 23 NPK factorial experiment to examine how long it takes before the soil supplies of N, P and K get depleted when no nutrients are applied, and whether selected crop types respond differently to applied nutrients.