over 120,000 tons of finfish, primarily Nile tilapia. Earthen ponds, mostly operated by small-scale farmers, dominate the aquaculture landscape. Nile tilapia is widely cultured due to its fast growth, environmental tolerance, and flexible diet. However, wide regional disparities in tilapia growth and survival persist, even under similar temperature and feeding conditions. This suggests other influencing factors, such as soil-water interactions, which remain poorly understood by farmers. Accordingly, this study investigated the role of soil properties in influencing fish growth and yield in earthen pond aquaculture systems in Uganda.
Soil samples were collected from pond farms across Uganda, particularly in the Northern and Central regions. A 60-day controlled experiment was conducted at the Aquaculture Research and Development Centre, Kajjansi, using six soil treatments and one control (no soil), set in triplicate groups, each replicate stocked with 80 Nile tilapia (average body weight: 1.54 g). All treatments were managed under identical feeding and environmental conditions. Soils from both regions were predominantly sandy clay loam, with no significant regional differences in texture. However, the treatment with the highest organic matter, cation exchange capacity, calcium, and potassium yielded the greatest factorial increase in fish body mass and the best feed conversion ratio (Table). This treatment also produced fish with the highest phytoplankton abundance in gut content. Interestingly, while the control exhibited the highest water column phytoplankton productivity and diversity, it yielded the lowest factorial increase in body mass and survival rate. This reveals that despite the importance of natural and artificial feeds in pond aquaculture, treatments that had soil all performed better than the control.
Therefore, soil properties significantly influence pond productivity and fish performance in earthen aquaculture systems. Despite often being overlooked, soil quality, particularly nutrient content and chemical characteristics can be a key limiting factor in Nile tilapia yields. Thus, this study underscores the need for integrated pond management approaches that incorporate soil testing and amendment practices to enhance aquaculture productivity in Uganda.