Age-dependent Changes in Soil Quality of Sodic Fish Ponds: A Comparative Study

Abstract

Pond-bottom soil plays a fundamental role in regulating nutrient availability, water quality, and biological productivity in aquaculture systems. However, prolonged pond use may alter soil fertility, salinity, and sodicity, making age-related assessment essential for effective pond management. This study assessed the nutrient status of bottom soils in aquaculture ponds, including pH, organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K), electrical conductivity (EC), and exchangeable sodium percentage (ESP), to support the optimisation of fish production and scientific pond management at the College of Fisheries Science, Ayodhya, Uttar Pradesh, India. Following a Z-shaped sampling pattern, soil samples were collected from newly constructed, five-year-old, and ten-year-old ponds and analysed using standard laboratory techniques. Pond age significantly affected soil quality (p < 0.05). Soil pH decreased from 8.9 in the newly constructed ponds to 8.1 in the ten-year-old ponds, while EC declined from 2.56 to 2.15 dS m⁻¹ and ESP decreased from 38.59 to 13.37, indicating a marked reduction in soil sodicity. In contrast, the ten-year-old ponds showed increases in organic carbon from 0.21% to 0.32%, available nitrogen from 262 to 282 kg ha⁻¹, phosphorus from 10.73 to 12.63 kg ha⁻¹, and potassium from 281 to 313 kg ha⁻¹. These findings indicate that prolonged aquaculture practices may increase organic carbon and nutrient availability while reducing soil salinity and sodicity, thereby improving bottom-soil fertility. The improved soil quality observed in older ponds may provide more favourable conditions for sustainable fish production and effective pond management.