Soil nitrogen V Leaching of nitrate from soils in laboratory experiments

Abstract The leaching of nitrate was studied by percolating water through columns of clay loam and sandy loam soils. The light soil lost nitrate more quickly than the heavy soil. For both heavy and light soils the rate of loss of nitrate from the soil into the leachate was initially greater from a coarse fraction (2-10 mm.) than from the unseparated soil. For the heavy soil a fine fraction (< 2 mm.) initially lost nitrate most quickly but ultimately the most nitrate was leached from the unseparated soil. When water was added slowly at the top of columns of unseparated soils until the bottom became wet, nitrate moved downwards, but not uniformly, as for both soils there was a minimum in the nitrate concentration near the bottom of the column. It is suggested that drainage water flows initially over the structural units, and not through the mass of soil until it is completely saturated, so that nitrate is first lost from the surface of the structural units and later from the soil mass as a whole. RESP-04214