Residual phytotoxicity effects of paraquat, glyphosate and glufosinate-ammonium herbicides in soils from field-treated plots

Soil residual phytotoxicity of commonly used herbicides in plantation crops in Malaysia were investigated through bioassay. Paraquat (Gramoxone) and glufosinate-ammonium (Basta) at 200, 400, 600 and 800 g a.i. per ha, and glyphosate (Round-up) at 400, 800, 1200 and 1600 g a.i. per ha were applied to field plots of 5 x 20 m2. Cucumber and corn were used in the bioassay to test the residual effect of herbicides in the soil of the treated plots. Soil, sampled at 1 day after treatment (DAT) and until 2 weeks (WAT) later, did not affect the seed germination and seedling development of cucumber and corn. Recommended rates, paraquat (400-600 g a.i. per ha), glufosinate-ammonium (500 g a.i.per ha) and glyphosate (1000 g a.i. per ha) applied to field to control weeds in oil palm plantation, therefore leave no phytotoxic residue in the soil.