The results of research about the development of hydrogensulfide in water and mud at the bottom in models for raising penseus monodon on orthi – thionic gleysoils in Ca Mau province

Abstract

      This paper introduces some experimenting results about H2S concentration on some production models for raising Penaeus monodon: Extensive Improvement Farming Model (QCCT), intensive farming model(CN) and rice - shrimp model (TL) on Orthi - thionic Gleysols in Ho Thi Ky and Thoi Binh villages in Thoi Binh District, Ca Mau Province. Sampling is carried out at two points at each place: in mud at the bottom of ponds, in water by the bottom, from August to December in 2007. The results through 5 times surveying show that: the concentration of hydrogensulfide is higher than the concentration that is lost equillibrium (LE: 0.1 ppm) and dead instantly (ID: 4ppm) of monodon shrimp. The average concentration of hydrogensulfide in three models are the highest in September and October and decrease by degree in November and December. The algae dead in water environment may cause high average concentration of hydrogensulfide at the periods. The average concentration of hydrogensulfide in mud at the bottom of ponds and in water by the bottom in three models are: CN (0,421 ppm - 4,88 ppm) and (0,320 ppm - 2,52 ppm); QCCT(0,179 ppm - 42 ppm) and ( 0,00 ppm - 3,73 ppm); TL( 0,674 ppm - 98,5 ppm) and ( 0,00 ppm - 2,04 ppm). High concentration of hydrogensulfide may cause low shrimp productivity. The productivity in CN, QCCT and TL model is lower the productivity in Alluvial solls like following: CN ( 1,5 ton/ha/crop), QCCT (69 kg/ha/crop) and TL( 88 kg/ha/crop), while in Alluvial solls: CN( 2-3 ton/ha/crop), QCCT (260 kg/ha/crop) and TL( 250 - 300 kg/ha/crop). To raise Penaeus monodon effectively, we must care about applying methods that can ameliorate the environment of mud at the bottom and water quality to control the concentration of ammonia in each model, example: put down lime periodly, control the organic, pH, send oxygen down bottom of pond...