EFFECT OF AGRICULTURAL RESIDUES ON AQUATIC FAUNA

Abstract

Nodorn agriculture is largely dependent on the extensive use of pesticides and fertilizers to increase crop. yield. These chemicals are not, completely assimilated by the soil and plants and some portion is left as residues. These residues find their way to natural water resources and adversely affect their quality and the flora and fauna. It is thus considered important to investigate quantitatively the effects these residues produce in receiving water. In the present investigation the combined toxic effect of pesticides and fertilizers have been determined. Seventy—two hour static bioassay tests. using Colisa faciatus as test fish and tap water as dilution water have been carried out. Dimecron and Aldrin pesticides and Urea and Diammonium phosphate ferti-lizers have been used in the-study. Six test runs, with Dimecron and. Aldrin separately and in conjunction with Urea and Diammonium phosphate, have been conducted to evaluate the synergistic and antagonistic effects of these chemicals and to fix up the toxicity level on the fish. Dimecron has been found to be less toxic to the test fish. Aldrin is significantly more toxic than Dimecron. The effect of addition of fertilizers .(Urea and DAP) to Dimecron is antagonistic and to Aldrin is synergistic. The combination of Aldrin and DAP has been found to be more synergistic than that of Urea and Aldrin. There is not much difference in the toxicity levels of Diniecron—irea and Dimecron—DAP combinations. 10 significant difference was found in median tolerance limit values obtained by Standard practice.and those with be fit regression. Harmless concentration has also been worked out