The Effect of Plotting on Leaching Uniformity of Soil Profile in Laboratory Model

In an experiment, the effect of soil surface plotting on leachinguniformity of soil profile was investigated. The experiment was performed in a physical model with dimensions (height×width×length) of 1×0.5×2 meters. The leaching of the soil profile was simulated in presence of subsurface drainage pipe. The plots were made by separating the soil surface into four equal parts (with dimensions of 0.5×0.5 m), in order to prevent water mixing on the soil surface. An equal water depth was applied for soil leaching, before and after soil surface plotting. After leaching, the ECe of soil samples taken from different depths (20, 40 and 60 cm) and different distances from the drain pipe (25, 75, 125 and 175 cm) were measured. The amount of standard deviation of soil salinity data were 2(dS/m) and 0.63(dS/m) before and after soil surface plotting, respectively. The uniformity coefficient of salinity distribution in the soil profile before and after soil surface plotting was estimated to be 45% and 76%, respectively. The results showed that the presence of drain pipe was effective on infiltration rate at different parts of the soil surface. So that the infiltration rate was estimated to be 1.9, 1.7, 1.56 and 1.47 (mm/h) at 25, 75, 125 and 175 cm far from the drain pipe, respectively. Through soil plotting, the unbalanced water infiltration to the soil surface was prevented, in order to have a uniform soil washing at different places. The results showed that the soil leaching uniformity can be achieved by adopting a management strategy. Therefore, more drainage water production, depletion of soil nutrients and environmental pollution are prevented.