it depends on the density of organic and aqueous layer what are the solvents that used in your work?

@Saleem Nasir I have used nutrient broth which contains insecticide dose after centrifuge I added an equal amount of ethyl acetate.

ethyl acetate will be the upper layer while aqueous one will be lower

@saleem Nasir it means upper layer is organic phase?

All organic solvents are less dense than water and they constitute the upper phase, except for halogenated solvents, like DCM (d= 1.33 g/mL) or chloroform (d= 1.49 g/mL). Thus, halogenated solvents constitute the lower phase of a biphasic (water/organic solvent) mixture