Abstract

Weeds becomes an undesirable plant grown in oil palm area that affects plant growth and development, therefore, it must be removed. The objective of this study was to evaluate the rainfastness of herbicide potassium glyphosate 440 g/l in controlling dominant weeds of oil palm plantation. The weeds, namely, Ageratum conyzoides, Borreria alata, Paspalum conjugatum and Imperata cylindrica at the same fresh weight having 2–3 leaves were planted in a plastic and store in the green house for one month, then moved out into plot size of 4 x 4 m and the herbicide was applied with the following rainfall intervals: (a) 4 h (b) 3 h, (c) 2 h, (d) 1 h before rainfall applying, (e) directly rainfall applied after herbicide application, (f) apply herbicide without any rainfall and (g) without application of herbicide and without rainfall. The results showed that the interval needed between herbicide application and rainfall was different among weed species. Broad leaf weed species, such as Ageratum conizoides required rainfree period 0–1 h, whereas Borreria alata required rainfree period of 2 h. Weed grass species: Imperata cylindrica and Paspalum conyugatum required rainfree period of 3 h.