TESTING A NITROGEN FERTILIZER APPLICATOR DESIGNED TO REDUCE LEACHING LOSSES

Abstract

Conventional practices for nitrogen fertilization of corn produce soil conditions that are conducive to preferential water flow and nitrate leaching. A new fertilizer applicator is proposed that will more effectively protect the fertilizer from infiltrating water and thus reduce the potential for leaching. The device forms a small compacted layer of soil above the subsurface fertilizer band and then mounds soil into a surface dome directly above the fertilizer band. This new localized compaction and doming (LCD) method is evaluated by measuring soil physical properties around the fertilizer band and comparing them with measurements made within the conventional knifing system. The LCD applicator increased penetration resistance from 0.50 to 0.75 MPa at the fertilizer band. As the knife slit above the fertilizer band was closed by the LCD applicator, soil bulk density was increased from 1.2 to 1.4 g/cm3 in the region. The ponded infiltration rate through the fertilizer band was reduced from 19.7 cm/h at the conventional knife slit to 10.1 cm/h at the LCD surface. Reduced water flow through the fertilizer band will result in reduced NO3-N movement. Nitrate movement was measured during a growing season in a corn field, and NO3-N applied by the LCD applicator moved approximately 60% as deep as NO3-N applied by a conventional knife applicator. The ability to restrict NO3-N movement by modifying the surface soil at N application represents a simple yet effective strategy to reduce NO3-N leaching losses and possible impacts on groundwater quality.