Water Retention and Pore Size Distribution of a Biopolymeric-Amended Loam Soil

The pore size distribution (PSD) of biopolymeric-amended soils is rarely investigated due to difficulties in its quantification using classical methods. In this study, we analyzed the impact of biopolymeric soil amendments on the PSD of a dryland loamy soil based on its physical and biological properties using a completely randomized design with four treatments consisting of two different dosages (10 and 5 g kg−1) of two different biopolymers, (chitosan [CH] and Arabic gum [AG]) plus a reference soil. To determine the effects of CH and AG on the PSD, nuclear magnetic resonance relaxometry (NMRR) measurements were used to determine the longitudinal (T1) and transversal (T2) relaxation times. A set of soil structure–related characteristics was also determined in the laboratory. The results revealed that T2 spectra provided a good proxy to determine the PSD, showing good agreement between the PSD from T2 spectra and that calculated from the water retention curve (WRC) (R2 > 0.78; RMSE