Yuwadee Sudthikara, Duangporn Kantachote, and Banjong Wittayaweerasak

pp. 25 - 35

Abstract

Bacterial numbers involved in the nitrogen cycle and some physicochemical properties in sediments of 4 intensive shrimp ponds, that had been cultivated continuously for 3 and 5 years, were studied between November 2004 to February 2005. The parameters were monitored as follows:, pH, electrical conductivity, organic matter, total Kjeldahl nitrogen (TKN), C/N ratio, ammonium, nitrite, and nitrate. The only significant differences (p < 0.05) found between the two types of ponds were ammonium (5.06-18.49 mg-N/kg
dry weight). Comparisons among these shrimp ponds and control soils indicated that shrimp cultivation significantly increased the soil pH (5.66-7.57, p < 0.05) due to accumulation of ammonium in the sediments. Bacterial populations were determined in control soils and 2 levels of sediments (0-5 cm, > 5-10 cm ) for both types of pond. Total numbers were in the order of heterotrophic plate count > azotobacteraceae >ammonifiers > denitrifiers > ammonium oxidizing bacteria > nitrite oxidizing bacteria.No significant difference was found between each bacterial group in the 2 levels of sediments from each sample set. In pond sediments from both sets of ponds organic matter was highly correlated with TKN (r = 0.783, p < 0.05,r = 0.883, p <0.01 ) indicating that ammonia release and the increase pH in the sediments was to some extent determined by the deposit of organic matter.