"We need to improve our weed management system in soybeans," states Palle Pedersen, Iowa State University Extension soybean agronomist.  He adds, "The challenge today is our weed management program is so efficient that we often take weed management for granted since we know we can kill any weed. The problem is we often spray the weeds too late. I personally believe weeds are the most yield-limiting pest we have in Iowa fields today. Soybeans are not strong competitors with weeds in the early part of the season. Many weeds can and will outgrow soybeans."

Control weeds vs. manage weeds!

Controlling weeds early is extremely important for successful soybean production, he says. Weeds compete directly with soybean for nutrients, moisture and light, thus reducing yield. They can also harbor insects and many diseases. It is true that soybean yield losses resulting from weed interference and the cost of weed control don't constitute the highest costs involved in soybean production anymore. "For example, we spend more than twice as much per acre today on seed than we spend on herbicides: just like corn," he says. "However, my goal is that I want to get maximum yield, and maximum yield is not possible when weeds are present; therefore, we must manage weeds early. I spray my research plots with a pre-emergence herbicide and again with a minimum of one post-emergence application, simply because I don't want to give up any yield." Successful weed management is a high priority today and should be in the future, says Pedersen. "I know everybody wants to simplify his or her weed management system. Most people want to do it all in no more than two passes. You can do that if you time the herbicide applications right. I was not very impressed with Iowa soybean fields in 2009, as they had a lot of weeds. And with $10 per bushel soybeans, we just cannot afford to give up any bushels!"