EFFECT OF DIFFERENT DOSES OF INORGANIC FERTILIZERS ON WATER QUALITY, PRIMARY PRODUCTIVITY AND PRODUCTION OF NILE TILAPIA (OREOCHROMIS NILOTICUS L.) IN EARTHEN PONDS

Document Type : Original Article

Authors

1 Central Laboratory for Aquaculture Research, Agricultural Research Centre, Ministry of Agricultural, Dokki, Giza, Egypt

2 Faculty of Science, Zagazig University, Egypt

Abstract

Earthen ponds (surface area 155 m2 each) were used to study the effect of different doses of inorganic fertilizer on water quality and fish production. Each pond was stocked with 150 fish of Nile tilapia; Ore­ochromis niloticus (25-30 gifish). The ponds received inorganic fertilizer (20:20:5 N:P:K) with doses of 0, 20, 40, 60 and 100 kg/fed/mth. The obtained results revealed that there were no significant differences in water temperature, dissolved oxygen, pH value, free ammonia water con­ductivity, nitrate concentration, total hardness, and total alkalinity due to the effect of different doses of inorganic fertilizer. Only Secchi disk reading, orthophosphate concentration and total nitrogen were signifi­cantly affected by treatments. Chlorophyll 'a' content over all the rear­ing period was increased by increasing the applied doses and the highest one was obtained with using 100 kg/fedirnth. The optimum production of Nile tilapia was obtained with the dose of 60 kglfed/mth. Data of car­cass proximate analysis showed that there were no significant differenc­es in dry matter, while crude protein total lipids and ash contents dif­fered significantly by different doses.