Kornertrags-, stickstoffbilanz- und energieeffizienzorientierte Stickstoffmineraldüngung von Körnermais in einem Langzeitdüngungsversuch in der Steiermark

At a high-yield site in southern Styria, a long-term nitrogen (N) fertilization trial was conducted over ten experimental years (2011–2016, 2018, 2020–2022) to investigate grain yield, N balance and energy efficiency in eleven mineral-fertilized treatments with 115, 145, 180, 210 and 240 kg N/ha, as well as an unfertilized control, with respect to the optimal N fertilizer rate. Calcium ammonium nitrate was used for all fertilizer rates. At an application rate of 180 kg N/ha, different fertilizer types (calcium ammonium nitrate, Linzer STAR, ENTEC® 26, urea), application times and numbers of split applications were additionally compared. Grain yield and N content in the grain increased with N fertilization, while the highest N rates no longer showed any additional effect. Nitrogen fertilization also increased the N balance (sum of N fertilization minus N uptake), and improved energy use efficiency (ENE = energy output/energy input). However, very high N rates strongly increased the N balance and led to a decrease of the ENE. The optimal N rates for a balanced N balance were calculated at 139 kg N/ha and for the highest ENE at 167 kg N/ha. The value of the ENE is in line with national recommendations for appropriate fertilization. Anyhow, an optimal, site-adapted N fertilization rate should be based from an ecological point on the N balance. At a fertilization rate of 180 kg N/ha, the different variants had no effect on grain yield and only a minor effect on N balance and energy efficiency.