Fig. 5. Sensitivity of the effective porosity (_e) to changes in organic matter (OM) contents, at selected sand contents (5–95% by 10% increments), as estimated from three different data sets, using sand and clay content (%) and OM content (%) as input. The range of soils is shown for which the estimated _e decreases when the OM content is increased. Different colors designate soils with different levels of sand content. (EUR–the European data set; HUN–the Hungarian data set; USA–the U.S. data set).