Evaluation of nitrogen-fertilizer recommendations for sugarbeet on the nitrogen-index expert system

Besides variety and environmental conditions, the nitrogen (N) fertilization is a major factor influencing the financial profit of the sugar beet crop. In Belgium, concerns about quality as measured by sugar content and extractability have led to increasing pressure from the sugar industry to promote fertilization systems which guarantee high crop quality. N-INDEX is a N-advisory system, developed to calculate optimal N fertilizer rates that take into account the expected N supply by the soil itself throughout the growing season. The calculation of the available N is based on the mineral N content of the soil at sowing time as well as on a range of other factors estimating the N mineralisation during the growing period (Vandendriessche et al., 1992; Geypens et al., 1994). N-INDEX is built empirically and is continuously refined both by new field trials and feedback from practice. This poster presents the results of a study carried out in 1996 to evaluate the effectiveness of N fertilizer recommendations based on N-INDEX with respect to production levels, quality, and financial return of the sugar beet crop at farm level.