Assessment of Soil Factors Influencing Productivity of Fish Ponds Under Two Contrast Agro-ecological Regions

The bottom soils of fish ponds not only influence the availability of different nutrient elements to benefit the primary food organisms but also control many important bio-geo-chemical reactions in the pond environment exerting significant influence on the pond health and, in turn, the fish growth. However, little attention is generally paid to various productivity attributing soil properties while undertaking any aquaculture operation in various soil zones. We assessed the relative effects of different soil factors on productivity of the fish ponds situated under two contrast agro-ecological regions of West Bengal, India, viz. hot-dry sub-humid (HDSH) region represented by red and lateritic soils and hot-moist sub-humid (HMSH) region exemplified by alluvial soils with the primary objectives of identifying the productivity limiting soil properties of the fish ponds of these two regions and understanding their impacts on productivity. For this, the magnitude of primary fish food production in 85 and 110 no of ponds in HMSH and HDSH regions, under culture of composite fish species, were studied in the form of net primary productivity (NPP) and correlated with relevant properties of those pond soils. NPP values were considerably lower in the fish ponds under HDSH region as compared to those under HMSH region. Statistical correlation and multiple regression analyses showed pH and available N and P status to be the key soil factors to influence the NPP of pond water in case of hot-moist region. For the hot-dry region, pH, organic C, available N and P, and clay content emerged as the major factors influencing the productivity. Among all these properties, available P was observed to be the most important soil factor influencing the net primary productivity of pond water in both the agro-ecological regions and was followed by soil pH and available N. Together, these three soil properties could explain 83 and 72% of variability in primary productivity of the fish ponds under hot-moist and hot-dry regions, respectively. The results suggest that the aquaculture practices in these two agro-ecological regions need specific management of these three soil properties for attaining better fish production.