Short-term effects of bio-fertilizers application on some soil physical and chemical properties

Bio-fertilizers can affect soil structure by affecting soil porosity and aggregate stability. In fact, the activity of soil microorganisms, in addition to their effects on plant roots, has significant effects on organic compounds and, in most cases, soil structure. Therefore, the aim of this study was to investigate the effect of bio-fertilizers namely mycorrhiza fungi (Glomus mosseae) and rhizobium (Mesorhizobium caesar) separately and together on some physical (bulk density and soil porosity) and chemical (Soil reaction, electrical conductivity and cation exchange capacity) properties of soil under greenhouse and field conditions, which has been less studied, so far. Because the application of bio-fertilizers in the soil can be one of the best ways to maintain and improve the physical and chemical quality of the soil.

In order to investigate the effect of Mycorrhiza fungi and Rhizobium on some chemical and physical properties of soil, an experiment was conducted in both field and greenhouse conditions in a completely randomized-block design with three replications. Mycorrhizal fungi specie Glomus mosseae, rhizobium (Mesorhizobium), mycorrhiza - rhizobium and control (no bio-fertilizer) were the treatments at the field condition. Sterilized mycorrhiza background material and non-plant (non-bio-fertilizer) were the two additional treatments in the greenhouse condition. The plant cultivated in this experiment was chickpea. At the end of the growing season, disturbed and undisturbed soil samples were taken from different depths and physical and chemical soil properties, mentioned above, were measured.

In the field and greenhouse conditions, mycorrhiza treatment reduced soil pH. Different treatments had no significant effect on cation exchange capacity under greenhouse and field conditions. Probably because, the cation exchange capacity associated with the soil specific surface area. In the greenhouse condition, the lowest bulk density at the first depth 0-5 cm (p < 0.05) was observed in pots containing mycorrhiza-rhizobium treatments (1.30 g cm-3) and mycorrhiza (1.36 g cm-3) and the highest bulk density was observed in the control treatment without plant and without inoculation (1.49 g cm-3). Also, treatments containing bio-fertilizer significantly increased soil porosity compared to the control without plant. So that, in the first depth 0-5 cm, the mycorrhiza × rhizobium bacteria treatment (0.50 cm3cm-3), in the depth 5-10 cm, the mycorrhiza treatment (0.49 cm3cm-3) and in the third depth (10-15 cm), all three bio-fertilizer treatments, had the highest porosity. The field conditions reduced the effects of the treatments on the soil physical properties, which may be due to the less impact of the treatments applied due to the large extent of the area and the uncontrolled environmental conditions.

Since different bio-fertilizer treatments had different effects on rooting depth and plant yield, the effect of the different treatments on soil structure improvement was different in different depths. In general, treatments containing bio-fertilizers improved the soil physical parameters and structure by affecting plant and root yield.