Determination of Deltamethrin & Dimethoate in Tea Soil

Tea plantations prefers to grow best in acidic soil conditions and they are subjected to ravages of insects, mites, plant pathogens, nematodes, caterpillar, termites and beetles. Pesticide is an important agricultural input for controlling array of pest complex in tea crop. The pesticides during its spray on tea bushes can enter the ecosystem by leaching into soil. An experiment was undertaken to assess the behaviour of deltamethrin and dimethoate in tea soil followed by its comparative laboratory study. The results for dimethoate revealed that residue decline during wet season (not detected on 5th day after spray) could be due to moist soil while during dry season (0.31-0.04-Treatment 1 and 0.60-0.06- Treatment (2 on 7th day) the loss in dimethoate concentration from the soil surface could be attributed to evaporation from dry soil surface. For deltamethrin the sunlight might have accelerated the decline during dry season (1.02-0.05-T1 and 1.95-0.28-T2 on 3rd day after spray).Further, during wet season, the residue loss was 0.19-0.06-T1 and 0.30-0.10-T2) high soil water partitioning indicated a relatively low potential for loss due to volatilization. The results obtained in field studies were further confirmed by laboratory studies which explained the effect of temperature, photo degradation and soil pH on the pesticide under study.