Someone who visited Mark Lawson's cornfield near Danville last summer when plants were still growing, before the heat and drought sent everything into the survival mode, might have wondered if he was piloting a new way to play golf. He had green carpet, basically the kind used on many miniature golf course greens, laid down between corn rows in certain plots, with no carpet in between other rows.
He wasn't playing golf, at least not between corn rows. The farmer and Syngenta agronomy services rep was trying to learn more about how early competition affects corn plants. He was, in effect, mimicking weed competition.
Wait a minute – carpet doesn't hog all the water and nutrients. That's true, but Lawson was demonstrating that's not the only way early competition from green, growing weeds between rows hurt plants. They affect the light reflectance. Corn plants depend upon light reflectance to determine if they have competition or not. Reflectance off a green surface tells them there is competition in the vicinity. The plants react by growing taller.
He eventually removed the carpet, like you would kill weeds with a post emergence herbicide application. But the damage was already done. The plants in the rows with carpet between them were taller, but their root systems weren't nearly as developed. There was definitely less root mass.
What happened was that when the plants sensed the signal to grow taller to outcompete plants for light, they used up nutrients and water to send the plant higher. This was water and nutrients that should have went into developing roots under the ground.
Since last year was so extreme and the plot couldn't be carried to yield, Lawson intends to repeat the experiment on his farm again this year. He hopes to get more quantitative data on how much the restricted root mass can mean to plants in a more normal year.