Résumé
Application of different types of feeds, fertilisers or food based nutrients in ponds results in the accumulation of high levels nitrogen, phosphorous and organic carbon in water and bottom soil. Farmers can use pond water as an irrigation source while soil as a fertility source of agriculture. This study was conducted at Sahas village on Dumuria upazila at Khulna district in Bangladesh for 46 days (from April to May, 2017) with nursery reared tilapia fingerlings in aforementioned earthen ponds using two different composition of commercial fish feed (diet-1 & diet-2) varying crude protein content 24% and 35% with different C and N content respectably as main plot treatment and three different amount 0 kg, 3 kg, 6 kg of each diets as sub plot treatment with six replications in split plot experimental design. In this study of aquaculture farming from initial about 6-8% organic carbon, 23-35% total nitrogen, 22-45% total phosphorous stored in pond sediments while 10-20% of available potassium and 2-3% of C/N ratio depleted from it. About 16-20% available nitrogen, 7-10% available phosphorous stored in pond water while about 8-9% dissolved organic carbon, 3-18% available potassium and 2-5% C/N ratio were depleted from it. Nutrient enrichment of pond water and soil during aquaculture production is insufficient to meet crop nutrient demand but fertiliser recommendations for crops should be altered when pond water is used as an irrigation source and pond bottom sediments used as fertility soil for in situ cultivation or excavate it to other field for growing crops and cost may reduce.