A Laboratory Test on the Effect of Subsurface Drain Installation Depth on Nitrate Leaching from a Loamy Sand Soil

Pipe drain installation depth is one of the most important design parameters، which has a key role in the drained water volume and quality. In this research، the effect of pipe drain installation depth was investigated by using a physical laboratory model. Drains were installed at 0. 25، 0. 5 and 0. 85 m deep in a cubical box with dimensions of 1*0. 5*1 meter filled with a sandy loam soil. Nitrate، nitrite، ammonium، and ammonia as well as drained water volume were measured. The results showed that maximum nitrate concentration increased with increase in installation depth. The observed nitrate concentrations for depths of 0. 25، 0. 5، and 0. 85 m were 51. 54، 105. 45 and 296. 42 mg/L، respectively. In addition، drained water volumes for depths of 0. 5 and 0. 85 m were 26% and 30% of the drained water volume of 0. 25m depth، respectively. Therefore، it can be noted that decrease in installation depth caused a reduction in nitrate leaching amounts.