Effect of irrigation with treated waste water on some physical and chemical properties of calcareous soil and on growth and heavy metals content of some fodder trees

Abstract EN

A greenhouse experiment was carried out to study the effect of secondary treated waste water on some physical and chemical properties of calcareous soil (sandy clay loam in texture) and on the growth and accumulation of some nutrient elements and heavy metals contents of three fodder trees (Acasia saligna, Acacia stenophylla and Ceratonia siliqud).

Data showed that using secondary effluent in irrigation have an improving effect on soil physical and chemical properties which enhanced fodder trees growth.

Results of the studied soil physical properties showed that percentage of macro water stable aggregates, optimum size aggregate, mean weight diameter (MWD) and structure coefficient (SC), as well as water holding pores and fine pores significantly increased by prolonged irrigation with secondary effluent up to 18 months, compared with tap water under the studied trees.

While values of fine water stable aggregates (<0.25mrn), quickly drainable pores and the specific surface area decreased.

Results ofvSoil chemical analysis indicated that soil pH, decreased and EC values slightly increased, while SAR did not varied by using secondary effluent as a source of irrigation.

Soil available N, P and K, as well as Fe, Mn, Zn and Cu and heavy metals (Pb, Cd, Cr and Ni) increased with using secondary effluent as a source of irrigation.

Vegetative growth parameters (height, stem diameter, fresh and dry weight) and elements content in leaves of the three tree species (N, P, K, Fe, Zn, Mn, Cu, Pb, Cd, Cr and Ni) increased with prolonged irrigation period by secondary effluent comparing with tap water (control).

The response of trees growth to irrigation with secondary effluent was in the order; Acacia stenophylla > Acacia saligra > Ceratonia siliqua.

Content of both micronutrient and heavy metals in leaves of trees were within the permissible limits and below the toxic level, which encourage using such water for fodder trees irrigation under the conditions of the present study.

Acacia stenophylla was the most responded tree for irrigation with secondary effluent.

So, it is recommended to be planted in calcareous soil in western coastal region, instead of wasting such water in the sea.

Key words: irrigation, waste water, calcareous soil, heavy metals