Water retention in ponds and the improvement of its quality during carp production / Retencjonowanie wody w stawach oraz poprawa jej jakości w procesie produkcji karpiowej

Abstract

Abstract Ponds play various functions both productive and non-productive. It was demonstrated in the paper that ponds retain water and during heavy rainfalls they act as a flood control measure. Self-purification of water takes place along the pond. Statistically significant reduction of nitrate-N, phosphate-P and calcium concentrations was found in pond water. From 102±24 to as much as 360±53 kg nitrate-N per ha of fishpond is retained during fish growth. Phosphorus may not be retained in fishpond; if it is then the amounts of stored P are small (from 1 to 7 kg·ha-1 on average). Slightly more potassium may remain in the pond. After the period of fish growth and draining the pond, only part of stored load of nutrients reaches the recipient water body. From 200 to 400 kg N-NO3 and up to 2300 kg Ca per ha does not flow out of the pond. The outflow of ammonium-N, phosphorus and potassium may, however, increase or decrease