The Cost of Uncontrolled Weeds

There are several aspects of agronomic decisions that have to be considered before committing to a weed control program for the upcoming season. Once a grower makes their choice of crop and variety, which includes technology in major row crops, they still have several decisions to make.

• What are the soil characteristics such as percent organic matter, texture and pH?
• What will the rotation crop be?
• What herbicides will be used?
• Will there be preplant, pre-emergence and post applications?
• How much will my herbicide program cost?

All these questions have to be addressed before planting season. Resistant weed populations along with other problematic weeds almost mandate the only feasible way to manage weeds and maximize yield potential is to utilize residual and contact herbicides prior to and throughout the growing season. If the right choices are made, the program should only consist of three key applications: 1) pre-plant burndown with residual, 2) pre-emergence residual, and 3) post residual and contact herbicide.

The cost of your weed control program is also an important consideration. Instead of asking, “How much does it cost,” the question should be, “How much will uncontrolled weeds really cost?” There have been numerous studies on weed competition in a number of crops since the onset of Weed Science as a discipline of study.  In Figure 1, corn yield loss due to weed competition is shown as influenced by growth stage and nitrogen level. Figure 2 shows soybean yield loss due to weed competition relative to growth stage and row spacing. Both graphs use 5% yield loss as the critical time for weed removal. Once the 5% critical level is met, you can expect an additional 2% yield loss for every growth stage (Knezevic, S.Z., et al., 2003).

Although these examples are for corn and soybean, you can expect similar trends for all annual row crops. The general conclusion is that weeds left uncontrolled will rob a crop of vital nutrients, available water, and sometimes sun-light, resulting in lost yield. Lost yield equals lost revenue.

It pays to use a pre-emergence herbicide at planting as part of a comprehensive weed management program to keep your crop weed free and maximize yield potential and profitability. In order to get the best performance out of your pre-emergence herbicides, you need to ensure that the applications are on target, maximize deposition, improve soil adsorption, and minimize leaching of the active ingredients. Grounded® is the perfect adjuvant to add to all your pre-emergence herbicide applications. Grounded is truly a multi-functional, oil-based adjuvant designed to keep your herbicide on target as well as hold it in the critical weed germination zone longer, thus giving pre-emergence herbicides the greatest chance for maximum performance.

Source: Knezevic, S. Z., Evans, S. P., Mainz, M. 2003. Yield penalty due to delayed weed control in corn and soybean. Online. Crop Management doi:10.1094/CM-2003-0219-01-RS.