Big weeds, waiting to spray means more yield loss

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

Last season, researchers at the University of Missouri conducted the first year of a two-year survey to identify the most common weed species encountered in Missouri corn and soybean fields, and also to better understand the management practices that producers utilize for the control of these species. This survey was primarily conducted throughout the northern half of the state across 50 different locations in 2011, and will be conducted in even more locations throughout the state in 2012. In a previous article, we described our results pertaining to the most common weeds that we found in Missouri corn and soybean fields in 2011. In this article, we will explain our findings as it relates to some of the management practices that producers utilize in Missouri soybean production systems.

As one component of this survey, we used the WeedSOFT computer program to estimate soybean yield loss based on the weed species and density of weeds present in each field just prior to the time of the post-emergence herbicide application. WeedSOFT is a program developed by a number of weed scientists at universities throughout the U.S., and is available online free of charge. To use this tool for yourself, simply go to and click on the yield loss calculator. Once there, all you have to do is enter the size and density of weed species in your field, and you will be able to see the yield loss that may have already occurred in your fields, or the weed loss that will occur if you delay your post-emergence herbicide application to subsequent soybean growth stages.

click image to zoomFigure 1. Estimated soybean yield losses incurred by the time of the first post-emergence herbicide application in the 2011 Missouri survey locations. The dashed red line indicates the average yield loss incurred across all surveyed locations. Labels next to each bar indicate the soybean growth stage at which the post-emergence herbicide application was made. -------------------------------------------------------------------------------- As illustrated in Figure 1, based on the weed species and densities present at the time of the post-emergence herbicide applications, we estimated that soybean yield losses ranged from 0 to 7.4 Bu/Acre at the 2011 survey locations. Also, across all the survey locations we were able to determine that the average soybean yield loss incurred as a result of waiting too long to make post-emergence herbicide applications was 2.7 Bu/Acre (Figure 1).

The point of this data is simple; it illustrates that in many Missouri soybean fields we are losing yield as a result of early-season weed competition and waiting too long to make our post-emergence herbicide applications. One of the fundamental principles of weed science is that the more weeds there are and the bigger these weeds get, the more yield loss we will experience. To some extent, this principle is also illustrated in the results from last year's survey contained in Figure 1. Although this figure does not show the weed density at each location, it does show the time that the post-emergence herbicide applications were made. For the most part, herbicide applications made to soybeans in the later stages of growth resulted in higher yield loss than those made at earlier stages of growth.

So, as you consider the timing of your post-emergence herbicide application in soybean this season, consider the price of a bushel of soybeans and what a 2 or even 3 Bu/Acre yield loss means to you. There are plenty of companies promoting various practices that will "enhance" yield by 2 or 3 Bu/Acre; our data indicate that in many Missouri soybean fields, we may be losing this much yield to weed competition.

Prev 1 2 Next All

Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...

Related Articles

No matching related articles at this time.

Comments (0) Leave a comment 

e-Mail (required)


characters left

Smooth Wall Grain Bins

Meridian’s SmoothWall bins are the ultimate storage bins, used to handle and store fertilizer, grain, feed and seed, and extend ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form