Impact of Initial Tilapia (Oreochromis niloticus) Stocking Size on Crop-Fish Yield and Soil-Water Quality in Integrated Rice-Fish Farming Systems

Abstract

Integrated rice-fish farming (IRFF) is a system of producing fish in combination with paddy cultivation using the same resources in the same unit area. This study aimed to assess the effects of different initial tilapia (Oreochromis niloticus L.) stocking sizes on the growth and yield of rice and fish, economic return, and to evaluate soil fertility and water quality within an IRFF system. A field experiment was conducted using four (T1-T4) stocking sizes: T1:5 g, T2:20 g, T3:35 g, and T4:50 g. Each treatment with three replicates was randomly allocated in a Complete Randomized Block Design. Data were analyzed using ANOVA and Duncan’s post hoc test. Stocking sizes influenced both rice and fish performance significantly. The 35 g and 50 g provided the best balance, supporting high yields for both rice and fish without adverse effects on soil fertility or water quality. The 50 g treatment produced the highest rice yield (5.08 t/ha), presenting a 1.8% increase compared to the average regional rice yield (4.99 t/ha). Soil nutrient levels (N, P, K) and organic matter (OM) significantly increased across treatments, with T4 showing the highest enrichment. Water quality parameters including pH (7.36-7.80), EC (376-383 µS/cm), temperature (29.26-29.40 ºC), DO (4.72-5.08 mg/L^-1), NO₃^- (0.61-0.86 mg/L^-1), and NH₃ (0.23-0.34 mg/L^-1) remained within non-toxic limits. The 50 g stocking size yielded the highest net return (USD 1,047.54 ha^-1) and benefit-to-cost ratio (BCR) of 1.44, presenting a 290 % increase in profit and a 19 % higher BCR compared to rice monoculture. In conclusion, this study suggests that 35 g and 50 g tilapia stocking sizes optimize rice-fish yields and enhance soil quality without compromising water quality in IRFF systems.

Keywords: Integration, Nutrients, Profitability, Stocking size, Sustainable agriculture