There is an increasing need for accessible methods to monitor soil health. Our primary objective was to compare an accessible, do-it-yourself method for measuring the maximum water holding capacity (MWHC) – we call the funnel, filter paper, and drainage (FFPD) method – to the water desorption method via pressure cells (PCs) routinely used for generating soil water retention curves. Secondarily, we tested the sensitivity of the FFPD to methodological variations. We compared the FFPD and water desorption methods using 10 soils from a wide range of soil textures (~4% and 55% clay). The two methods were quite comparable in precision, with mean coefficient of variances of 3.5% and 4.4% for the FFPD and water desorption method respectively. The FFPD method compares best with PCs at the wetter end of water retention curves (-2.45 kPa) and is considerably wetter than what is often considered water holding capacity (or -10 to -33 kPa). The FFPD method is somewhat sensitive to some methodological modifications, notably variation in water source, but overall is consistent and with standardized protocols could be scientifically robust. Overall, this test that has long been used by soil biologists and ecologists can also be used as a simple and affordable test of MWHC of soils, thereby enhancing soil health monitoring and enabling greater use as an educational tool.
