Abstract
2, 4-D dimethylamine at 22.4g a. i./a and ametryne at 11.2g a. i./a were applied on waterhyacinth in 150 liter- 60cm deep plastic pots in the greenhouse on July 9th, 1979. Dissolved oxygen, water temperature, pH, total suspended matter, chemical oxygen demand, organic and inorganic carbon, chlorophyll a, soluble orthophosphate and ammonia nitrogen were assayed at 15 and 45cm depths for 126 days after the application. 2, 4-D gave complete kill for waterhyacinth plants 3 weeks after application while ametryne treated plants were partially killed. The decomposition of waterhyacinth as a result of 2, 4-D application resulted in changes in water quality: oxygen depletion from 2 to 8 weeks after application; production of algae and phytoplankton; release of carbon compounds; phosphorus and ammonia production; and increase in pH, chemical oxygen demand and suspended matter. Maximum water pollution indicated by these parameters occurred 12-14 weeks after application. Differeneces in water quality between treatments and untreated control are presented.
