Prior to 1973 we had 38" bean rows. Our corn was 40" & we shoved our row units in on the 490/494/495 planters to get 38" beans. I think we did it for canopy. We were operating an organic farm back then...just didn't have the title or market though...it was all cultivated. Had to shove in the cultivators to cultivate the beans after the corn was done. Seemed like we were always shoving big iron things around. Corn & beans did OK.

1973 we went to 30" corn & beans. Corn did good, beans did good. We were still semi-organic. Used some Amiben on the beans (granular herbicide), but still cultivated the beans. Didn't shove as much iron around....corn & beans did OK.

1976 we started a 12 yr run of pure no-till. No longer organic anything. Drilled beans were 7.5" first, then later got a 10" row drill, then another 7.5" drill. About '88 we got a 15/30" Kinze Twin Line. Planted corn 30", beans 15". Corn & beans did OK.

We changed brands & went to the the JD 15/30" row planters. Corn & beans did OK.

In about 2010, we went back to pure 30" row beans. Just like going back to 1976 when corn & beans did OK. Since we've been straight 30" corn & beans, the yields have been OK. Haven't seen any weed problems that I'd blame on wide rows. Biggest change we've made in the past 40 yrs of bean planting is reducing populations. We were spilling 200-240K/a when we first went to drills. I do remember with the 494/495 planters we'd try for "8-10 beans per foot" in 38" wide rows.

I think you'll find the folks w/narrow row planters believe in them. I think you'll find most folks w/the 30" row corn/bean planters have been down the narrow row road & have now come back to 30". Not sure anyone's 100% correct.