Effect of Irrigation of Turfgrass With Treated Domestic Effluent on Nitrogen Contents in Soil and Plant

Irrigation with treated effluent is one of the most important aspects of utilization of effluent as an available water resources. Experiment was conducted for investigating the effect of irrigation with treated effluent on nitrogen contents in soil and turfgrass. Three typical different turfgrass species and two irrigation methods (subsurface drip irrigation and subsurface irrigation with porous pipe) were adopted in the experiment with treated effluent and potable water, which was 12 treatments totally. Before the irrigation, the source of domestic effluent is treated by a special facility which includes a sand filter with volume of 2 m×1.5 m×2.2 m and a settlement pond with scale of 2 m×1.5 m×1.4 m. Results indicate that the contents of total nitrogen (TN), ammonium-nitrogen (NH⁺₄-N) and available nitrogen (AN) in soil of root zone (0～30 cm below the soil surface) after irrigation with effluent are slightly lower than those after irrigation with potable water. However, the nitrate-nitrogen (NO^-₃-N) content in and below the root zone soil is much higher than that after irrigation with potable water, and average content of TN in plant after irrigation with effluent is approximately 50% higher than that after irrigation with potable water. The contents of NO^-₃-N in soil layers especially in the layers of 15～30 cm and 30～45 cm below surface with sub-drip irrigation of effluent are higher than that after subsurface irrigation with porous pipe with effluent, but there are no differences in contents of TN, NH⁺₄-N and AN in soil between the two irrigation methods.