Comparative study on the dissipation of thiram in two type of soils at oil palm (Elaeis guineensis jacq.) nursery

Abstract

The dithiocarbamate fungicide thiram is extensively used in oil palm (Elaeis guineensis Jacq.) nurseries for protecting oil palm seedlings from diseases caused by Melanconium, Glomerella and Rhizoctonia sp. The factors affecting thiram dissipation were studied under tropical conditions at two experimental sites situated in oil palm nurseries with two soil types namely: Clay loam and sandy clay loam. The field experimental plots were treated with thiram at two dosages (using the knapsack sprayers) (1) at the recommended dosage (25.6 g ai plot-1) and (2) at double the recommended dosage (51.2 g ai plot-1). Thiram residue was detected in the sandy clay loam and clay loam soils on treatment day (0 day) and from 1 to 3 d after treatment (DAT), respectively. The level of residue detected increased in soil depth. The results demonstrated that thiram dissipation was influenced by soil properties such as organic matter and clay content, and preferential flow was found to be the main pathway of thiram in the soil profile. The dissipation of thiram residue was observed in both the clay loam and sandy clay loam soils, to the depth of 50 and 30 cm of the soil profile, respectively, and the half-life was found to be less than 1 d. These findings suggest that thiram is safe for use as a foliar application on oil palm seedlings due to its short life span in the soil and its low risk potential for groundwater contamination.