Method for repairing contaminated soil through arranging powder ridge underdrain system

The invention discloses a method for repairing contaminated soil through arranging a powder ridge underdrain system. The method comprises the following steps: during powder ridge tillage, using traightly-arranged powder ridge mechanical screw drill bits in which one drill bit (or two drill bits) in the middle is lengthened to form a concave strip-shaped ditch on the layer surface of a plough pan below a tillage and soil loosening layer in the powder ridge tillage process; cleaning the ditch in the powder ridge process, placing a certain thickness (such as 2-3 centimeters) of weeds or tree branches in the ditch, adopting manual ditch digging on the periphery of a field (a plot of land), and forming a drainage and pollution discharge port to form a pollution discharge network system below the tillage and soil loosening layer so as to facilitate pollution discharge; enabling soil contaminated by heavy metals, residual chemical fertilizers, pesticides and the like to be sunk to the junction of the bottom of the power ridge soil loosening layer and the plough pan along with moisture through soaking and leaching of natural rainfall or manual irrigation and then to be sunk to the concave strip-shaped ditch through the layer surface, so as to remove pollutants through the pollution discharge network system formed by the powder ridge tillage to achieve the purpose of reducing pollution and repairing the soil.