Nitrogen cycling and retention in fish-cum-livestock ponds

Synthesizing the results of 18 PhD studies carried out at the Fisheries Research Institute in Szarvas, Hungary, on fish-cum-pig and fish-cum-duck ponds, the nitrogen cycles in these organically loaded ecosystems were constructed. Data for 13 water and sediment nitrogen components, including is solved and particulate matter, combined and freely dissolved amino acids and dissolved and ‘absorbed’ sediment total ammonia concentrations, were quantitatively analysed. All known nitrogen transfer rates were determined simultaneously or estimated through mechanisms of nitrogen balance: nitrogen fixation, ammonification, ammonia regeneration, amino acid uptake, ammonia uptake, nitrification, nitrate uptake, nitrate respiration and denitrification. Based on management parameters as well as compartment and transfer rate measurements, the nitrogen balance and budgets were also calculated for the experimental ponds and for a fish-cum-duck commercial farm. The farm nitrogen budget was determined by analysing 20 years of nitrogen input-output data. The analysis shows the high assimilative capacity of the fish-cum-livestock ecosystems for nutrients, indicating the possible buffer function of the system in highly utilized agricultural areas.