Comparison of water quality in rotation of shrimp - rice farming system in Ca Mau and Tien Giang provinces, Vietnam
The study on the fluctuation of water quality in rotation of shrimp-rice farming system in Ca Mau and Tien Giang provinces, this is the coastal region in the Western and Eastern the Mekong Delta, some regions of these provinces have fluctuated saline following the season, land in the rainy season is used for growing paddy rice, but saline has appeared in the dry season, this land is alternated with growing of Black Tiger Shrimp.
The study was conducted in year of 2013 in Thoi Binh district of Ca Mau province and Tan Phu Dong district of Tien Giang province. Three farms in each district are selected for the study, area of each farm ranges from 0.5-2.4 ha. There are 6 times of sampling included two times in rice crop, and fourth times in shrimp crop. Sampled sites are collected in both of the inlet canals and the flat-forms of each farm. Postlarvae density stocking is 4 individual / m2 without feeding, they are PL 15 from the shrimp hatcheries. Parameters in each the waters include salinity, temperature, DO, COD, BOD, TN and TP and yield of shrimp. Results found that it has different about operating of farming system in two districts because of various natural conditions. Furthermore, there are fluctuations about water quality in temporal and spatial aspects, yield of shrimp and period of culture is also different in two locations. Depth of canals is 1.2-3.3m and flat form is 0.4m, the temperature fluctuated 26-30.50C, salinity oscillated 1.0-30.0 ppt. Besides, dissolve oxygen ranges from 4.3-6.5mg/L, COD is 1.2- 16.4 mg/L, TN and TP are 0.5-2.6 mg/l and 0.2-0.7mg/L, respectively. In addition, relative of environmental parameters and yield of shrimp are also discussed in the study.