INFLUÊNCIA DA ESTAÇÃO DO ANO E DO FERTILIZANTE APLICADO NA PRODUÇÃO ORGÂNICA DE TANQUES DE CRIAÇÃO DE PEIXES . I PRODUÇÃO PRIMÁRIA

The experiment was set up in 12 ponds of similar dimensions (5.0 x 9.0 x 1.2 m) of Fish Culture Section of Faculdade de Ciencias Agrarias e Veterinarias da UNESP, Campus de Jaboticabal Each pond was stocked with 95 Cyprinus carpio, Sarotherodon niloticus and hybrid tilapia fingerlings during 60 days in 1977's summer and winter seasons. Trials consisted on fish pond fertilization as follows: 1. Rabbit manure at the level of 0.5 t/ha.month plus the inorganic fertilizers ammonium sulphate (50 kg N/ha) and simple superphosphate at the level of 20 kg P/ha.year; 2. The same organic manure supplemented only with ammonium sulphate; 3. The same organic manure plus simple superphosphate at the same level of the treatment 1; and 4. Control (no fertilization). Each treatment with 3 repplicates was plotted entirely at random among the 12 experimental ponds. Meteorological and hydrological (chemical and physical water conditions) parameters and also biological data such as phytoplancton standing-stock and primary production were weekly determined. Great seasonal variations were observed qualitative and quantitatively due to nutrient recycling in the pond water, that was responsible for the larger organic production in ponds during the summer season. Concerning to N and P nutrients only N fertilization (with or without P) increased organic production at all levels in the ponds.