Researchers at Iowa State University have released two studies demonstrating the benefits of crop canopy for controlling weeds.
One study examined the effect of soybean planting density on weed management. The results showed that weed biomass was related to soybean population, with each increase of 100 soybean plants reducing weed biomass by 26 lbs/A.
The other study found that the canopy was as effective as herbicide in the area within 12" of either side of the row. The only significant weed growth occurred were the canopy had not developed sufficiently by mid-June. The research indicates that had the rows been planted at 15" width rather than 30" width this would have limited the weeds that came up.
SOURCE: Iowa State University.