R. KALCHEV1, D. TERZIYSKI2, A. STOEVA2 and G. GROZEV2
1 Institute of Zoology, Bulgarian Academy of Sciences, BG - 1000 Sofia, Bulgaria
2 Institute of Fisheries and Aquaculture, Varna, Branch Plovdiv, BG - 4003 Plovdiv, Bulgaria
KALCHEV, R., D. TERZIYSKI, A. STOEVA and G. GROZEV, 2006. Nutrients and other chemical variables, related to plankton primary production in fertilized and control fish ponds. Bulg. J. Agric. Sci., 12: 226-235
Polyculture earthen fishponds stocked with common, grass and silver carps were fertilized with cattle manure applied in 3000 kg.ha-1 per vegetation season. Several variables (solar radiation, water temperature, Secchi depth transparency, oxygen, phosphate, ammonium and nitrate concentrations, pH, permanganate oxydability, N.P-1 ratio and gross plankton primary production) were registered at approximately bi-weekly intervals. Variance analysis revealed a week difference between control and fertilized ponds for phosphate and ammonium concentrations only for level of significance between 0.05 and 0.1. Plankton primary production of treated fishpond as dependent variable delivered a highly significant multiple linear regression with nitrogen or nitrogen to phosphorus ratio and water temperature. In control ponds no such relationship emerged.