Influence of growing plants and nitrogen fertilizer on saturated hydraulic conductivity

Abstract

A field experiment was conducted on a sandy loam (typic Hapludoll) to test the effect of maize (Zea mays L.) and nitrogen (N) fertilizers on soil saturated hydraulic conductivity (Ksat). Half of the plots were planted to maize and the other half were kept unplanted. All the plots were fertilized at the rate of 75 kg ha‐1, with two fertilizers differing in their acidity index [calcium ammonium nitrate (CAN)=16 and ammonium sulphate (AS)=111]. Undisturbed topsoil samples were taken at the time of maize harvest to determine soil Ksat in the laboratory. Total organic carbon (TOC) and soluble carbon (SC), pH (1:2.5), and the electrical conductivity (EC) of soil saturated extract were determined in grounded and sieved soil samples. The Ksat reached the highest values under maize fertilized with AS. Most of the variation of soil Ksat was determined by the increment of soil salinity. So, soil permeability improvements were caused by a greater flocculation of soil colloids because of saline effects. Soil pH decrease caused by these acid N sources did not provoke the dissolution of organic matter because none of the carbon (C)‐forms measured in the experiment were affected by the fertilization. Thus, other C‐compounds different from those here measured might be improving soil permeability.