ABSTRACT
Summary At present the most hazardous pollution phenomenon in groundwaters is the nitrateproblem. The extent of N-removal will determine the feasibility of most sludge application projects. From a practical standpoint, the annual loading rate can be estimated using a N-mass balance. The annual loading rate can be adjusted in accordance with proper monitoring technique. The upper limit for nitrogen fertilizers has been emphasized to be 100 kg/N/ha, when the groundwater pollution is hindered.
