One of the most important replacement methods used instead of chemical herbicide and
conventional tillage is cover and companion crops’ application which is a major factor in sustainable
agriculture. In order to determine the best cover crop in controlling weeds of corn field and its
further effects on corn yield, an experiment was carried out in a factorial arrangement based on
RCB design with three replicates. The treatments of this experiment included companion crops (clover,
hairy vetch, basil and dill) as first factor and time of sowing cover and medicinal plant (synchronic
sowing with corn and sowing 15 days after corn sowing) as second factor. The results
showed that ear weight, ear length, leaf weight, grain length and yield were significantly influenced
by companion crops and sowing date. Whereas, weed biomass was influenced by cover crop
type · sowing date interaction. Also, the results indicated that increasing biomass weed resulted
in linear reduction of grain yield. The highest ear weight, ear length, leaf weight, grain length
and yield were obtained for cultivation of clover with corn. Synchronic cultivation of companion
crops with corn had higher grain length and yield compared with cultivation 15 days after corn.
The lowest weed biomass was recorded for concurrent cultivation of corn with clover due to rapid
growth and high competitive power of clover in the early stage of growth.