Strategies for site-specific nitrogen fertilization with respect to long-term environmental demands

Long-term field trials were implemented in three regions of Germany, differing in climatic conditions and soil properties, to evaluate different site-specific nitrogen fertilization approaches over several years with regard to N efficiency, yield and environment. The strategies tested were mapping approaches on the basis of site-specific yield potential and spectral information and, alternatively, an on-line approach using the Hydro N sensor. Results from the first year are presented. N efficiency could be increased by mapping approaches on sites with low yield potential. Total yield however was not noticeably affected. Sensor based N application reduced variability in the field but only slightly increased total yield. On the other hand, N efficiency was significantly reduced on shallow soils. The first results indicate that including yield potential in site-specific N recommendation could be an essential step to make plant nutrition more environmentally sound.