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

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 siliqua). 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 (<0.25mm),
quickly drainable pores and the specific surface area decreased.
Results of soil 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.
EFFECT OF IRRIGATION WITH TREATED WASTE WATER650
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.