Arabic Gum Effects on Some of Physical and Chemical Properties of Loam and Clay Loam Soils

There are controversial reports about the physical, chemical and biological properties of biofilms modified soils. Although there is no report on comparing the effects of Arabic gum on different soil textures, reports of different biopolymer effects as potential analogues of biofilms in different soils are contradictory. We assume that the soil texture class, as its intrinsic property, may affect the effects of various soil amendment. Therefore, in order to evaluate the performance of Arabic gum in two different soil texture classes, the present study was conducted to investigate the effects of Arabic gum as a similar to biofilm (extracellular polysaccharides) on several soil characteristics in loam and clay loam soils. For this study, two different soil types including clay loam and loam texture classes, a factorial experiment in a completely randomized design (CRD) were carried out with two factors including soil type and different amounts of Arabic gum (0, 5 and 10 g per kg of soil) and three replications and two observations. Then, after the incubation stage of the treated soils, the disturbed and undisturbed soil samples were collected from the pots and prepared for measuring the bulk density, soil moisture content, hydraulic conductivity, saturated water content, soil aggregate stability (WAS), mean weight of aggregate diameter (MWD), mass fractal of aggregates, soil acidity (pH), organic carbon content, cation exchange capacity, and microbial respiration. The results showed that the effect of Arabic gum on saturated moisture content, soil bulk density, saturated hydraulic conductivity, and microbial activity in loam soil was lower than that of clay loam. The use of Arabic gum in clay loam soil increased by approximately 12, 18 and 317 percent, respectively, in the saturated volumetric and gravimetric water contents and the saturated hydraulic conductivity. While having very little effect on these properties in the loam soils. The use of Arabic gum also reduced the bulk density of clay loam soil, while no changes were found in the loam soils. Also, in treated soils, Arabic gum showed positive changes in soil organic carbon and the stability, size, and mass fraction dimension of aggregates, being independent from soil type. Considering that less variation was observed in the properties of loam texture (which is courser than clay loam soils), we recommend the use of a higher amount of Arabic gum (greater than 10 g kg-1) in coarse texture soils or its use with residues of organic matter to have significant effects on these soils.