Significance of the treated sewage water as an alternative source for irrigating some newly reclaimed desert soils

الملخص EN

A greenhouse pot experiment was carried out on some marginal desert soils of sandy and calcareous in nature cultivated with alfalfa plants for studying the impact of applied treated sewage water as an alternative irrigation source on soil and grown plant characteristics as compared to the fresh Nile water .

The data obtained show that soil bulk density tends to decrease vs an increase in each of total porosity and available water as a result of applied treated sewage water for both studied soils.

However, soil permeability shows a dual relationship for both studied soils as affected by the applied irrigation resource, where hydraulic conductivity value tended to decrease in the sandy soil vs an increase in the calcareous one.

These results were supported by a parallel decrease or increase in soil drainable pores for sandy and calcareous soils, respectively.

This trend could be ascribed to the physio-chemical action of suspended organic colloidal particles that modified soil structure, throughout increasing both meso and micro-pores (< 9.0 ?) in sandy soil, and in turn to increase its ability to retain water.

On the contrary, increasing macro-pores (3000.0-9.0 ?), which enhanced excess water removed by drainage from the calcareous soil.

In general, applying the treated sewage water caused an increase for soil organic matter content and CEC in sandy soil,as well as, a decrease for soil pH and ESP values in calcareous soil.

Also, results indicate that this water quality was surpassed the Nile fresh for improving the fertility status (availability of plant nutrients) of the studied newly reclaimed sandy and calcareous soils, due to it attains a relatively high content of both organic matter and essential macro- & micronutrients for plants.

The dry matter yield of the grown alfalfa was enhanced by the addition of applied treated sewage water, especially for the studied sandy soil as compared to the calcareous one.

This may be attributed to the high content of CaCO3 in the latter soil, which restrict the nutrients availability and in turn, reduced the vegetative growth of alfalfa.

Data of N, P, K, Fe, Mn, Zn, Cu and B contents in alfalfa plants responded positively to the applied treated sewage water as being as a source of nutritional elements, as well as, the relatively high content of suspended organic constituents (humic and fulvic acids) have a pronounced benefit effect on the biological characteristics of soil.

However, Cd, Ni, Pb and Co taken up by alfalfa plants did not exceeded the permissible limits.