Water Table Management as a Natural Bioremediation Technique of Nitrate Pollution

Nitrate-nitrogen (NO3--N) pollution of water resources is a worldwide problem. Field trials were conducted from 1997 to 1998 to investigate the combined impacts of water table management (WTM) and N fertilization rate on soil NO3--N level and concentration of NO3--N in drainage water. Treatments consisted of two water table treatments: free drainage (FD) with open drains at a 1.0-m depth from the soil surface and subirrigation (SI) with a design water table of 0.6 m below the soil surface, and two N fertilizer rates: 200 kg N ha-1 (N200) and 120 kg N ha-1 (N120) in a split-plot design. Subirrigation reduced NO3--N concentration in the soil compared to FD by 37% in the spring of 1997 but not significantly (2%) in 1998; and 45% and 19% in the fall of 1997 and 1998, respectively. Higher rates of fertilization (N200) resulted in greater levels of NO3--N in the soil profile than the N120. Nitrate-N concentrations in drainage water from SI were 74% and 80% lower than those from FD in 1997 and 1998, respectively. Water table management can effectively reduce NO3--N pollution of water.