The most traditional method to determine the soil-water retention curve is based on the Richards' pressure plate apparatus. For practical reasons, cheaper and faster alternatives to the Richards' apparatus are needed. Therefore, this study evaluated the use of the filter paper method. Initially, an Oxisol was sampled and physically characterized. Undisturbed soil samples were prepared and tested in Richards' chamber, at pressures of 0, 10, 30, 60, 100, 300, 500, 1,000 and 1,500 kPa. In the filter paper test, the water matric potential was measured in samples for which moisture levels had been determined by an appropriate calibration curve. The tests obtained pressure versus moisture points that were adjusted by the van Genuchten model, using the RETC program. A comparative analysis of the soil moisture values estimated by the model adjusted in the filter paper test and the adjusted retention curve obtained by the Richards' apparatus was performed. Results allowed the conclusion that the filter paper method is suited to determine the water retention curve of the agricultural soil studied.
Richards' pressure apparatus; alternative method; matric potential; soil moisture
