Stress in corn
“Weeds can fundamentally alter what the corn growth is and what it does. When weeds are there at corn emergence, they are really an immediate source of stress. So, as soon as they start to emerge the corn starts to react differently. The corn plants tend to try to outgrow those weeds, so they try to get taller. Unfortunately, the alternative thing that happens is we get a lack of root growth. So, you get a taller plant, less roots, and then a lot of times those corn plants will want to grow down the row, instead of out into the row. So, when you do that, you're just getting less sunlight and unfortunately it's not really optimum for a corn plant in early season.”
Threewits says there are some lesser-known consequences of having early-season weed competition.
“I think it goes back to this underdeveloped root system. So, we think about just above ground what we see, but it's really what's happening below ground. That additional stress, really you got less roots there for how the plant handles stress, how it can take up nutrients. And then even later on in the season how that hurts when we start having lack of moisture and high heat, or even insects. All those things can compound that problem for just having that less developed root system in the corn.”