Variation in Bottom Soil Quality with Increasing Pond Age in Freshwater Aquaculture

Abstract

Pond bottom soil quality is an interesting area to assess environmental impact of aquaculture. Aim of the present study was, therefore, to investigate effects of fish culture on quality of pond bottom soil. Ten excavated earthen ponds located in Lahore, Pakistan were divided into two groups; Group1: 23-32 years old and Group 2: 8-20 years old ponds. Mechanical and chemical methods were used to study particle size distribution and physico-chemical attributes of soil respectively. Surface sediment of ponds contained higher sand and lower clay content than that of deeper soil layers in both groups. pH of the soil was higher than 7.0 that ruled out the necessity to lime soil for neutralizing acidity. Salinity of surface soil was found to be significantly high (P<.05) compared to that of deeper layers. Organic carbon in surface soil of Group 1 ponds (3.35%) was significantly higher (P<.05) than that of Group 2 ponds (2.60%). Available phosphorous represented only 1-10% of total soil phosphorous. An interactive effect of pond age and soil depth was found on soil clay and electrical conductivity through factorial analysis. Results led to the conclusion that regular removal of sediment can maintain original quality of bottom soil.