Evaluating the Acid Soils for Aquaculture in Fish Pond Development in Akwa Ibom State, Southeastern Nigeria
Declining natural fish stocks due to over-exploitation of finite water resources and loss of habitats resulting from discharge of toxic contaminants, and increasing demand for fish products due to increasing population have necessitated the expansion of aquacultural development from aquatic ecosystems to upland ecosystems. Studies were conducted at seven representative locations to evaluate the suitability of the acid soils for aquaculture in pond development in Akwa Ibom State, Southeastern Nigeria. Morphologically, a hue of 7.5 YR typifies the upland soils. The soils have a weak, medium sub-augular blocky structure, and consistence varying from very friable in the topsoil to friable at lower profile depth. The predominant particle-size fraction is sand averaging between 73.9 and 85%, while the clay fraction ranges from 10.7 to 23.1%, and soil texture varies from sand to sandy clay loam. Average values of soil density varies from low (1.14 g/cm3) to high (1.66 g/cm3). Hydraulic conductivity (Ks) ranges from slow (1.01 cm/h) to rapid (8.31 cm/h). Infiltration rate at the soil surface and at 60 cm depth ranges from 4.80 to 84.8 cm/h and 0.78 to 2.16 cm/h respectively. Maximum available water capacity is low ranging from 5.57 to 11.92 cm. The soils are slightly acidic with pH ranging from 5.2 to 6.1. Electrical conductivity range from 0.01 to 0.057 dS/m. Organic C content varies from low (0.79%) to medium (1.29%). Available P ranges from low (7.12 mg/kg) to high (112.21 mg/kg). Effective CEC is generally low, mean profile values range from 5.25 to 7.92 cmol/kg. Base saturation is moderately low, averaging between 33.9 and 54.2%. The results show that the soils of the upland ecosystems are naturally unsuitable for earthen fish pond development. Remedial measures to alleviate the physical and chemical constraints to aquaculture in fish pond development have been discussed.
Keywords: Upland ecosystems, acid soils, soil characteristics, earthen fish pond development.