A Simple, Affordable, Do-It-Yourself Method for Measuring Soil Maximum Water Holding Capacity

There is an increasing need for accessible methods to monitor soil health. Our primary objective was to evaluate an accessible, do-it-yourself method for measuring the maximum water holding capacity - we call this the funnel, filter paper, and drainage (MWHCFFPD) method. First, we compared MWHCFFPD to the water desorption method via pressure cells (WHCPC), routinely used for generating soil water retention curves, using 10 soils from a wide range of textures (4-55% clay). Second, we tested the sensitivity of the MWHCFFPD to methodological variations likely encountered by citizen scientists. 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 MWHCFFPD and WHCPC methods were comparable, with MWHCFFPD best correlating to WHCPC at -2.45 kPa (R2 = 0.98). The MWHCFFPD method is somewhat sensitive to some methodological modifications, most notably variation in water source, but with standardized protocols could be scientifically robust. Overall, MWHCFFPD can be used as a simple and affordable test of sieved soil structure and organic matter, and thus has potential to expand soil health monitoring.