Nitrate residues, soil nitrogen balance and nitrogen fertilizer recommendations in vegetable fields in Flanders

In vegetable crops, an accurate nitrogen fertilization based on soil analysis is essential, both to optimize crop yields and to reduce nitrate residues after the crop and nitrate leaching during winter. The nitrate residue in autumn is determined by several factors. Crop N requirements and N uptake patterns play a significant role, as well as N stocks at the start of the cropping period, N mineralization from soil organic matter and plant residues and N fertilization. The calculation of soil mineral N balances taking into account the different N inputs and outputs in a crop can be very useful to detect the possible causes of excess nitrate-N residues after the crop. In this study, the major bottlenecks of vegetable growing in Flanders in terms of N fertilization and nitrate-N residues are discussed, based on the calculation of soil mineral N balances in three different vegetable fields with cauliflower and leek.