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Abstract
Biochemical, chemical and physical characteristics for both sandy and calcareous soils under the influence of different water holding capacity levels (WHC) were studied under different incubation periods.
Two laboratory experiments and two greenhouse experiments were executed to achieve the aim of this investigation. In first experiment, Chlorella pyrenoidosa and Nostoc muscorum were selected as best growing algal strains in the aqueous extracts of both sandy and calcareous soils. The second experiment was to select the favorite moisture contents (any of 25, 50, 75 and 100% of the soil water holding capacity [WHA] of both sandy and calcareous soils under sterilized and non-sterilized conditions. There were other two greenhouse experiments to evaluate the effect of algal inoculation under different soil moisture contents (75 and 100% WHC). The greenhouse experiments were incubated for 24 weeks and the first one was non-cultivated and the second was under tomato cultivation condition. The results revealed that algal inoculation under any of the tested WHC levels improved the soil biochemical properties such as and soil pigments (chlorophyll a &b and carotene) the soil enzyme activities (Acid phosphatase, Alkaline phosphatase, ATP-ase and dehydrogenase), soil chemical properties, since the electric conductivity decreased in both sandy and calcareous soils. Due to the soil physical properties, remarkable improvement in soil aggregates stability index were recorded in both sandy and calcareous soils against decreases in the soil aggregates instability index. Nevertheless, the improvement in soil characters in both sandy and calcareous soils was more pronounced in non-sterilized conditions than those of the sterilized ones. The enhancement of the soil characters was better under tomato cultivation conditions. However, these enhancements in such soil properties could by due to the exopolysaccharides secreted by algae into the soil. Exopolysaccharides were detected in both sandy and calcareous soil extracts and in the algal cells at different growth stages. The detected exopolysaccharides were momo- saccharides (fructose, glucose, ribose and xylose), di-saccharides (galactose, lactose, maltose and mannose) and tri-saccharides (raffinose); Algal inoculation can play an important role in improving the soil properties of the marginal poor soil such as sandy and calcareous soils.