Effects of Nitrate Solution on Soil Permeability and Salts Leaching

Abstract

Nitrate solution with several different pH were percolated into three kinds of soil columns under saturated conditions. These soils were Kantoh loam surface soil, subsoil and Yellow soil respectively. Main clay mineral of Kantoh loam was allophane and Yellow soil was kaolinites. The distribution of water pressure potential, pH of soil water and concentration of salts in the soil columns were measured. The results were as follows.
1) The soil permeability for Kantoh loam subsoil was decraesing with percolation time due to the dispersion of the soil particles at the surface of soil column.
2) The soil organic matter had the mechanism to control the dispersion of soil particles, so the reduction of soil permeability was small in the case of Kantoh loam surface soil.
3) Yellow soil particles were flocculated in low pH nitrate solution, so the reduction of soil permeability with time was small.
4) The soil surface area for ion exchange increased in proportion to the dispersion of soil particles. Then the quantity of salts displaced from the soil surface by the hydrogen ion increased in the case of soil particles dipsersed condition. The degree of salts leaching for Kantoh loam subsoil was large as compared with another two soils.