The study evaluated wheat, faba bean and onion uptake of Fe, Mn, Zn, Cu, Cd and Pb and characterized the microbial biomass and distribution in a soil under irrigation with sewage wastewater for 40 years at ElMadabegh, Assiut, Egypt.
With sewage wastewater irrigation concentrations of Fe, Mn, Zn and Cu in all crops are optimal for plant growth, but that of Cd and Pb were high. Compared to that irrigated with the Nile River fresh water, irrigation with sewage waste water resulted in lower dehydrogenase activity, soil respiration and microbial biomass carbon and higher quantities of bacteria, actinomycetes, fungi and denitryfing bacteria and decreased the quantities of nitrifying bacteria, Azotobacter bacteria and sulphere oxidizing bacteria.
In the rhizosphere of onion, the biomass of actinomycetes and fungi was lower, but that of bacteria was higher with sewage wastewater irrigation than with the Nile River fresh water irrigation. Lowest log numbers of fungi, denitryfing bacteria, nitrifying bacteria and Azotobacter bacteria were found in the rhizosphere of onion, but the log numbers of certain other bacteria and actinomycetes were not significantly different between the three crops.
These results showed high Pb and Cd concentrations in the crops irrigated with the sewage wastewater and that the sewage wastewater affected the quantity of common and functional microorganisms in the plant rhizosphere, but the magnitude of the microbial population is dependent on the crop type.