Abstract

The effect of adding sewage sludge on the productivity of cotton, wheat and corn and the accumulation of some heavy metals in soil and crops

Author(s): Omar Jouzdan, Gilani Abdelgawad, Awadis Arslan, Manhal Alzoabe, Nadia Bejon and Mohamed Altabaa

 This study was conducted in Al-Kamary station in Aleppo province in collaboration between the Arab center-ACSAD and the
General Commission for Scientific Agricultural Research in Syria, to study the effect of adding sewage sludge on soil properties
and on the productivity of cotton, wheat, and corn. The accumulation of heavy metals namely Cd, Cr, Ni, and Pb were monitored
into the soil and plant tissue of the studied crops during three subsequent seasons. Sewage sludge was added to the soil at rates
ranging between 6 and 15 ton/ha according to crop N requirement and when its content of heavy metals are less than the
thresholds. Yields from the sewage applied treatments were compared with the treatment received chemical fertilizers, and the
both of them were compared with the control which did not receive fertilizers or sewage sludge. The results indicated a significant
increase in the productivity of some crops grown in the soil received sewage sludge, and this increase reached 15% in cotton, 36%
in wheat grain, 16% in wheat straw and 47% in corn seeds compared with control. The increase in productivity also reached 2% in
cotton, 16% in wheat grain, 10% in wheat straw and 36% in corn compared with chemical fertilizer application. Increases in the
concentrations of heavy metals Pb, Ni, Cr, and Cd were 8.44, 122, 92, and 0.13 mg/kg, respectively in the soil received up to 15
ton/ha sewage sludge compared with control (5.42, 116, 95 and 0.07) mg/kg. However, these concentration remain within the
natural limits (0.1-2) mg/kg of Cd, (10-150) mg/kg Cr, (5-500) mg/kg Ni, and (2-200) mg/kg Pb. No significant increase in the
concentrations of the heavy metals in the plant tissues of the crops cultivated in soil received sewage sludge at a rate of 15 ton/ha.
The concentration of the heavy metals in the plant tissues remained in the natural range of concentration (0.05-1.20) mg/kg Cd,
(1-5) mg/kg Cr, (0-4) mg/kg Ni, and (0.1-30) mg/kg Pb, and far from the toxic and the harmful effects on human health according
to the international standards.