NITROGEN PROCESSING AND RETENTION IN HUNGARIAN CARP FARMS

Based upon a detailed study carried out 20 years ago on the sediment n itrogen content in the commercial carp ponds of Horvathpuszta intensiv e farm and upon the reexamination of the same 19 ponds, we found an av erage annual rate of nitrogen accumulation of 174 mu g N g(-1) dry sed iment. Nitrogen budgeting for the 20 years (1970-1990) was completed f or input nitrogen sources of inorganic fertilization, duck feed, fish feed, manure, atmospheric deposition, filling water and nitrogen fixat ion, as well as for output sources of alfalfa, fish, rice, duck yield, drainage water and denitrification. The average annual nitrogen reten tion of 93 kg ha(-1) corresponded well to the 174 mu g N g(-1) me of n itrogen accumulation. During the 20 years of nitrogen accumulation on industrialized agricultural land of Hungary, the intensive fish farm r eceived altogether 1246 tonnes of nitrogen and released only 686 tonne s to the environment. Therefore removing, processing and accumulating most of the available nitrogen while minimizing the pollution to the e nvironment is one of the challenges for the future for both aquacultur al and agricultural activities.