Agronomy Talk

Agronomy Update

Water Damage and Spraying Soybeans

Published on Thursday, June 25, 2015

Standing water from excessive rainfall this month has left some Ohio crops in a bad spot. Here are some of my favorite pictures from across our region.


In all seriousness, the wet June conditions could contribute to a number of potential concerns including nitrogen loss, stunting, crazy top, and crop death.

In this week’s video, we evaluate the London, Ohio Practical Farm Research (PFR)® tile spacing study and how well the different spacings have handled the 2.75 inches of rain we received over the weekend. In addition to what we are seeing with this study, this week’s video also covers best practices in managing nitrogen after all the rain, and how long crops can survive under water.


Spraying Soybeans

One question we hear a lot is “what does spraying cost me”? You might be thinking of herbicide cost, but I’m thinking of something else. If your row spacing is 15 inches or less, there is always yield loss when you post spray and run over plants. One study estimated losses at 2.5 percent with 60 foot booms, 1.9 percent with 90 foot booms, and 1.3 percent with 120 foot booms. That’s a $6.50/A. difference that may pay for the cost of your custom application, if you decide to have them spray with 120 foot booms instead of your 60 foot sprayer. In Beck's PFR study we saw a 5 Bu./A. yield loss by letting the fields get too weedy before post spraying. Spraying earlier means you are spraying smaller weeds and there will be less yield loss than if you are running over beans in the reproductive stages.

Another question we often get is "when is the best time to spray soybeans"? The herbicide label is the strongest guiding arm in this decision. For glyphosate tolerant and Roundup Ready 2 Yield® soybeans, the cutoff for spraying Roundup® is after growth stage R2, which means you shouldn’t spray once one of the four top nodes with a fully developed leaf has a 3/16-inch long pod. LibertyLink® soybeans are restricted to not spraying Liberty® once flowers are on the plant. Spraying when temperatures are warm, humidity is high, and adding AMS can all improve weed kill. Because Liberty is a contact herbicide, it’s important to use 15 to 20 gallons of carrier and get good coverage. Make sure to follow label instructions. Not only do we want to follow directions, but spraying “off label” is illegal. From the time you see the first bloom to the time you hit R3 is normally about 14 days.

Have you noticed that many recommendations have changed how much Roundup to post on your glyphosate tolerant and Roundup Ready 2 Yield soybeans? In an effort to control glyphosate resistance and hard-to-kill weeds, most people now recommend 32 ounces of Roundup instead of the 22 ounces many were accustomed to spraying, even though the label has stated to use a higher rate with bigger weeds. This does help, especially if weeds are larger, but many times the weeds that didn’t die with 22 ounces are still Roundup resistant and don’t die with 32 ounces.  

In Ohio, Marestail is a shining example and Palmer amaranth is an emerging example in parts of the state. If weed resistance has become a problem for you in your Roundup soybean system, consider your other options. For now, planting LibertyLink soybeans is your best alternative. New technologies such as Roundup® Xtend and Enlist Duo are on the horizon. Another very effective option is using a robust burndown with multiple modes of action that are effective on present weeds including a residual herbicide. Once you have made the decision to use residual herbicides in your program, study your weed pressure first. After determining your problem weeds, choose a herbicide that rates well for those troublesome weeds. 

After spraying burndown or residual herbicides a month ago, are the chemicals really cleaned out of the sprayer now? Sometimes I see yellow streaks in fields because the field was post sprayed while there was still some residual hanging in the sprayer hoses. As a quick test, pull a hose off of your nozzle body and see if anything is lying in there. Remember to use a tank cleaner and follow the directions – not just rely on spraying loads of roundup and figure it is clean after a few.  

What to add? There are all kinds of foliar feeds, fungicides and insecticides that can be sprayed. Remember that R3 is the best time to spray fungicide on soybeans. That means a separate application because Roundup or Liberty should be applied sooner than that. Foliar feeds have had mixed results, but shouldn’t be discounted completely. Through on-farm testing and Beck’s PFR studies, we are working to determine the times when you are most likely to benefit from these products. Even a small 1.6 Bu./A. yield gain such as we saw with Versa Max last year may be worth it if it is simply added to your post herbicide pass. Fungicides and insecticides have also shown yield benefits, but may also delay your soybean harvest because the fungicide keeps your plant healthier longer.

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Alex Johnson

Alex Johnson

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