The agronomical and physiological efficiency of nitrogen applied for arable crops in Poland

The common relation yield / nitrogen dose can be broken into two relations: nitrogen uptake / nitrogen dose and yield / nitrogen uptake. Such procedure narrows the original variation and separates it in two different and easier to recognise categories, external and internal. The results of permanent field experiments conducted in Poland with all the most important arable crops has been re-examined according to this idea. The model for fertilizer recommendations in respect to nitrogen was proposed.