Dissolution of fertilizer in Ando Soils

Abstract

Almost farm in southern part of Kyushu Island are covered by ando soils. In order to investigate transpotation of inorganic nitrogen dissolved from fertilizer, one dimensional unsaturated seepage tests are carried out under precipitation condition. The test columns are filled with ando soil picked up from the surface of actual farm in Mimata, Miyazaki. Experimental rainfall intensity is decided from the averaged monthly precipitation through April to August in Miyazaki. The fertilizers are added on the soil in both standard quantity and 167% quantity of standard on 12th day and 28th day, respectively. The sample water are collected every 4 days from the bottom of 20cm,50cm,100cm and 150cm columns. The concentration of NH₄⁺-N, NO₂^--N and NO₃^--N are measured by means of Ion Chromatograph or Spectrophotometer. From these measurements, the followings are clarified; that is, nitrification occurs in shallow place within 50cm depth. The concentration of NH₄⁺-N and NO₂^--N are quite low but that of NO₃^--N exceed 50ppm. The concentration of NO₃^--N increase in parallel to the quantity of fertilization.