Der Mineralstickstoffgehalt des Bodens als Maßstab für den Stickstoffdüngerbedarf (Nmin-Methode)

SummaryNitrogen supply in soil is divided into two components: the amount of mineral nitrogen in the root zone at the beginning of the growing season (Nmin content, kg N/ha) and the amount of nitrogen mineralized during the growing season.The objective of this research is to study the importance of Nmin content for the nitrogen fertilizer demand of winter wheat. Results of experiments on loess soils in NW Germany are:1.Before the growing season Nmin content (NO3−N and small amounts of NH4−N) of the soil layer 0 to 100 cm ranges from 20 to over 300 kg N/ha when precropped by cereals, sugar beets and vegetables.2.In the growing season plants utilize mineral nitrogen in the rooted soil like fertilizer nitrogen.3.Nmin content on no-N plots is closely related to growth, N uptake and yield.4.Field experiments to study the relationship between Nmin-content and the nitrogen demand resulted in fertilizer recommendations that take Nmin content into account. This method is now applied by farmers growing cereals.5.Application of this method to other soils and crops requires knowledge of: date of soil analysis, rooting depth, total nitrogen demand of the crop, mineralisation and leaching of nitrogen in the growing period.