The relationship between soil macropore and preferential flow was analyzed in different citrus land in Jiangjin District of Chongqing City using brilliant blue dye method with image processing techniques

water breakthrough curve

and the Poiseulle equation.The results showed that the steady effluent rate of the dye-stained area was 1.48 times higher than that of the dye-unstained area.The radii of soil macropores ranged from 0.3 mm to 1.7 mm.The path of preferential flows were mainly found in the macropores with radii larger than 0.7 mm.