Weed control efficiency: how effectively herbicide controls weeds
= (weed dry weight in weedy plot – weed dry weight in treated plot) x 100/ weed dry weight in weedy plot

Weed smother efficiency: how effectively intercrop suppresses weeds
= (weed dry weight in sole crop – weed dry weight in intercropped plot) x 100/ weed dry weight in sole crop

Weed index: yield loss in a treatment
= (Yield in weed free plot – yield in treated plot) x 100/ Yield in weed free plot