IN MEMORIAM – CHRIS DIRKSEN (1936-2017)

The well-known Dutch soil physicist Chris Dirksen passed away on September 17 2017. After completing his International relations degree at Wageningen University, in 1959 he and his wife Dicky Boeijenga moved to the USA. In 1964 Chris obtained his PhD degree at Cornell University, with a thesis on formation of ice lenses in unsaturated soil. Subsequently he was four years with Gulf Research and Development Company at Pittsburgh PA, working on natural convection during segregated burning. In the period 1968-1978, he was with the USDAARS, the first five years stationed at University of Wisconsin and next at the US Salinity Laboratory (USSL) in California. In 1978 Chris returned to Wageningen, first to Soil Science and Plant Nutrition and later on to Water Resources.

Throughout his career Chris developed novel laboratory and field methods to determine soil physical properties and monitor processes in unsaturated soils and response of plants to salinity and water stress. At Wageningen, he became much involved in teaching and organizing introductory and advanced soil physics courses. The book Soil Physics Measurements (Catena Verlag, 1999) reflects his promotion of sound methods. At Riverside Chris collected an impressive amount of data on the response of plants to salinity and water stress. At Wageningen he thoroughly analyzed those data, paying close attention to the hysteresis of the water retention curves. In the late 1990s, with colleagues he collected and analyzed more data on plant response to non-uniform, transient salinity and water stress.

By Peter Raats, Wageningen University