SITE-SPECIFIC NITROGEN-FERTILIZATION GPS, ELECTRONICS AND NITROGEN SIMULATION-MODELS

A site-specific nitrogen fertilization is necessary from an economical and an ecological point of view. The necessary technical equipment in cludes the use of DGPS, yield sensors on harvesters and electronics on tractor and fertilizer spreader and is well testet for practical oper ation. But there are many open questions concerning the correct way to calculate the fertilizer amounts. The first step is to identify and l ocalize homogeneous areas. The fertilzer amount for each area can be e stimated using simulation models for crop growth and nitrogen dynamics . This paper gives an overview about problems and solving strategies f or the identification of homogeneous areas. Because of the existing pr oblems of the practical use of nitrogen simulation models the resultin g stragtegies for the actual and further development of the simulation models are discussed.