Lysimeter studies on nitrogen transport and transformation as affected by contaminated water irrigation

Contaminated river water irrigation was conducted in two couples of lysimeters with 1 and 3.5 m soil depths, respectively, to identify factors affecting transport and transformation of organic matters and nitrogen compounds. During 2 months of experimentation, 372 kg/ha of total nitrogen mineralized into inorganic nitrogen. The amounts of nitrification and denitrification were as high as 387.8 and 321.8 kg/ha, respectively. 40.5 kg/ha of NO3--N leached into groundwater, which amounted to 78% of the initial NO3--N. Therefore, denitrification and the leaching are the main processes for the loss of nitrogen in soil. Soil moisture was a primary factor affecting the transport and transformation of nitrogen (N) compounds. Lysimeter studies demonstrate that chemical oxygen demand (COD) and NH4+-N concentrations changed with spatial and temporal variations of the water content and the concentration of NH4+-N is highly positively correlated with COD. However, there is no significant correlation between soil moisture and NO3--N, and the relationship between NH4+-N and NO3--N is poor.