Soil heavy metal residue under different treated waste-water irrigation technique and management

Different irrigation techniques (furrow irrigation and subsurface drip irrigation) and management (full irrigation and partial rootzone drying irrigation) were used to study heavy metal residue in soils irrigated with treated waste-water. The results show that Cd content in soils after harvest with full irrigation is higher than in that with partial rootzone drying irrigation under the same irrigation technique and water quality. Cd content in soils under subsurface drip irrigation with treated waste-water is higher than in those with treated waste-water and a few additional chloride; that under furrow irrigation with treated waste-water is higher than in soils with fresh water irrigation.Cd content in soils under full irrigation with treated waste-water and subsurface drip irrigation is lower than those with furrow irrigation. However, Cd content in soils with partial rootzone drying irrigation and subsurface drip irrigation is higher than in soils with furrow irrigation. Pb content exhibits the same trend as Cd for almost all the treatments, except that Pb content in soils under subsurface drip irrigation with treated waste-water is lower than that with treated waste-water and a few additional chloride; also those for soils under subsurface drip irrigation with treated waste-water are lower than for furrow irrigation under both partial rootzone drying irrigation and full irrigation. Soil Pb residue decreases under different treatments after harvest, while soil Cd residue under treated waste-water irrigation increases by 0.62%～7.78% after harvest (though it decreases under other treatments). The study provides a solid scientific guide for treated waste-water irrigation.