S13 - Session O5 - Improving N fertilization management in organic vegetable farming with decision support systems

Authors: Sarah Tietjen *, Konrad Egenolf, Rachel Fischer, André Sradnick

Decision support systems (DSS) are commonly discussed as a way to optimize nutrient management in open field vegetable farming. Here, a high nutrient demand has to be met in a short time span. In organic farming, nutrients are applied in organically bound form and released under site specific conditions at variable paces. Since DSSs are able to process large and diverse amounts of information, they can play a key role in fertilization management of organic vegetable farms through sustaining yields while avoiding negative environmental impacts from excess nutrient application. To assess the impact of the recommendation from DSSs on the applied amount of nitrogen (N) fertilization, field trials with cabbage ( Brassica spp.) and lettuce ( Lactuca sativa L. ) were conducted in three consecutive years (2019-2021). The on-farm trails were situated at 13 different locations throughout Germany. The farmers' N fertilization (business-as-usual) was compared with the recommendations according to N-Expert and NDICEA, two DSSs that were developed for vegetable farming. The fertilization according to the German legislation ordinance (DüV) was included as a fourth treatment. The amount of applied N in the business-as-usual treatment did not differ significantly (ANOVA with Scheffe-Post-Hoc Test, significant at p < 0.05) from the N-fertilization calculated with N-Expert or NDICEA for both cultivars. The N fertilization in the business-as-usual and NDICEA treatments was significantly lower than N fertilization according to DüV. The results of a comprehensive statistical analysis will be presented, including the impacts of the N fertilization according to the DSSs on yields and post-harvest mineral N concentration in the soil.