Studies on low productive rainfed brackishwater culture ponds along the periphery of chilka lake, orissa.

Abstract

A survey was conducted by collecting water and sediments from ten rainfed ponds of Khandualpur area situated along the periphery of Chilka lake to investigate the possible causative factors for the low production of Penaeus monodon (100457.5 kgMyr) and to consider ways and means to help augment production in such systems. Seasonal changes were studied during the monsoon and winter production cycles as also the resting summer period during the year 1988-89. The data on sediment characteristics reveal that organic carbon (0.17-0.66%), CaCO3 (nil-2.0%), available nitrogen (11.37-23.83 mg/100 g soil) and available phosphorus (1.62-6.34 mgI100 g soil) are indicative of low productivity. Among other factors, the exiremely low redox potential ((Eh:48*7 to -1601) mv) and very high iron content (0.90-1.85%) are probably limiting the production of prawn in these ponds. Further, the water quality and low nutrient status (phosphate 0.0111-0.012, nitrate 0.020-0.050 and alkalinity 22.G60.0 ppm), low salinity (5.0-10.0 ppt) and high iron content (0.92-2.68 ppm) also indicate low productivity. The very poor plankton and benthos density confm the poor productivity of these ponds. The sandy clay soil with a pH range of 5.6 to 9.4 can be better utilized with suitable management practices to overcome the low nutrient status and high iron content of soil and water. Possible measures for improving the productivity of the rainfed ponds are discussed