Movement of ammonia plus ammonium from nitrogen fertilizers band placed in alkaline soils

Abstract

Movement of NH₃ plus NH₄ ⁺ from nitrogen fertilizers, band placed either as crystals or as granules in alkaline soils, was determined. The pH values of these soils, whereof the clay contents ranged from 7,6 to 49,9%, were adjusted to approximately 8,8. Fertilizers like (NH₄)₂SO₄, LAN, urea, MAP and DAP were band placed in these soils with different water contents at different bulk densities. The application level was equivalent to 60 kg N ha⁻¹. After a contact period of 14 days the movement of NH₃ plus NH₄ ⁺ was determined. The distances that NH₃ plus NH₄ ⁺ moved from the plane of application varied between 45 and 100 mm. The results indicate that the movement of NH₄ ⁺ was small compared to the movement of NH₃. The major factor that controlled the degree of NH₃ movement in soil was the quantity of NH₄ ⁺ converted to NH₃. The conversion of NH₄ ⁺ to NH₃ was governed by the variable soil properties and the type of fertilizer. Both diffusion and convection contributed to the movement of NH₃.

Keywords:

• Ammonia
• ammonium
• convection
• diffusion
• movement