Evaluating fractal dimension of the soil particle size distributions and soil water retention curve obtained from soil texture components

It is much easier to measure solid phase data or particle size distribution (PSD) than pore size distribution, therefore it is useful to determine relationship between fractal dimension of the soil particle size distributions (DPSD) and soil water retention curve (DSWRC). The present research aims to firstly measure fractal dimension of the soil PSD using three radii 1 (clay), 25 (silt) and 1000 (sand) µm (DPSD3) and subsequently compare it with fractal dimension obtained from DPSD, and secondly develop a relationship between DPSD3 and DSWRC. The results showed that the maximum and minimum values for DPSD were 2.93 and 2.65 and for DPSD3 were 2.91 and 2.63 and there was no significant difference between DPSD3 and DPSD. A linear relationship between DPSD3 and DSWRC was developed for some of soils UNSODA databases. The relationship developed here was compared with three present methods to calculate DSWRC from soil texture including (1) non-linear relationship with clay, (2) logarithmic relationship with clay, and (3) percent of sand, silt and clay for some of the northern soil of Iran. The results indicated that the proposed method in this study, especially in fine-grained soils, can efficiently predict DSWRC with appropriate precision.