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October 2013 Archive for Ask an Agronomist

RSS By: Farm Journal Agronomists, Farm Journal

Have your agronomic questions answered by a Farm Journal agronomist. E-mail us directly at, and we’ll respond on this blog to provide an interactive dialogue.

Why was marestail so difficult to control this year in soybeans?

Oct 24, 2013

Question: I was really disappointed in my marestail control in soybeans this season, using a combination of glyphosate and 2,4-D.  I’d appreciate any advice you can offer for next year.

Answer:  You weren’t alone.  A lot of farmers had the same issue. Aaron Hager, University of Illinois Extension weed scientist, says soybean growers in the state saw an abundance of marestail for a couple of reasons. For one, inclement weather conditions when spring burndown herbicides were applied minimized control results. Second, the spread of glyphosate-resistant populations in the U.S. is making marestail more difficult to stop in its tracks.

Furthermore, marestail plants can produce an abundance of seed, up to 200,000 per plant. The individual seeds spread readily from field-to-field, Hager notes, because the plant’s design is adapted to wind movement. "If you have them in one field, chances are if they were able to make seed they’ll move within that field or out of that field to infest other geography or fields that perhaps never had the problem before," he says.

Bill Johnson, Purdue University Extension weed scientist, says his research during the past two years shows that farmers need to use multiple steps to control marestail in soybeans, especially herbicide-resistant species. "Two-shot burndown programs which include either two shots in the spring or fall plus spring burndown treatments are needed in areas with a history of poor marestail control due to glyphosate and ALS-herbicide resistance," notes Johnson.

Hager agrees and encourages farmers to start their marestail control practices this fall with an application of 2,4-D (1.0 lb. acid equivalent per acre), which can be applied through late November. Additional herbicides can be included in the tankmix, he says, to increase the number of winter annual species controlled.

Hager cautions that fields populated by marestail and treated with fall-applied herbicides won’t necessarily be free of the weed next spring. His advice: "Scout fall-treated fields before spring planting and plan to use supplemental herbicides and tillage to control any existing marestail plants.  Do not plant soybeans into an existing marestail population," he adds. "Apply residual herbicides close to planting time to control summer annual species, including spring-emerging marestail."


A Geographical Look at Weed Problems

Some weeds are prevalent in only certain areas of the country, while others seem to be everywhere. More than 1,500 farmers and ranchers shared their views in last week’s Farm Journal Pulse. The question was: What is your most significant weed problem? Waterhemp tops the list with 30% of respondents saying it was a problem. Marestail/horseweed was a close second with 22% of the votes.


Control Winter Weeds for Better Crops, Earlier Planting

Weather cycles of cold temperatures, abundant rain and short spurts of warmer, sunny days have allowed weeds such as chickweed, purple deadnettle, henbit, wild garlic, dandelions and marestail to flourish in the last few weeks.


Strategies to stay ahead of glyphosate resistance

Marestail is confirmed resistant to glyphosate, and Palmer pigweed also appears to be resistant. 


5 Tips for Effective Soil Testing

Oct 15, 2013

It’s a good idea to pull soil samples from the field every two years, Farm Journal associate field agronomist Missy Bauer says in Episode 12 of Corn College TV Season 3.

"That helps us keep pretty consistent on keeping up with the lime needs or the pH levels in the field as well as your overall P and K levels or micronutrients in these fields," Bauer says.

Follow five steps when taking those samples:

  1. Calibrate your probe to the depth specified by the laboratory that will be processing your soil samples.
  2. Sample consistently. Labs generally specify a depth between 6 2/3" and 8".
  3. Pull between 10 and 12 cores from each management zone.
  4. Store soils in separate bags, one per management zone.
  5. Use field computers and GPS to know where you’re at in the field.

Learn more about how to put these five steps into practice here:

Five Steps for Proper Soil Sampling

Follow these guidelines to prepare field samples for laboratory evaluation, says Farm Journal associate field agronomist Missy Bauer in Corn College TV Season 3.

The When, How and Why of the Soil Test

Reach into the farmer’s toolbox with Farm Journal Field Agronomist Ken Ferrie to learn the keys to soil sampling. Reinforce the importance of soil sample. In episode 4 of Corn College TV, reach into the farmer’s toolbox with Farm Journal Field Agronomist Ken Ferrie to learn the keys to soil sampling.


Ways to Improve Soil Health

These tips will keep your fields producing at their highest potential, Farm Journal associate field agronomist Missy Bauer tells Corn College TV Season 3.


Should I Use Fall Tillage On This Piece of Ground

Oct 03, 2013

 Question: I am taking over some very sloping and hilly ground for next year and can’t make up my mind if I want to rip it this fall for fear of erosion. The previous farmer chopped corn on it for silage consecutively for about 10 years. I have ran the chisel plow a couple passes, just to see what kind of condition the soil is in, and it is really dry. I am not getting very good shatter at all. There are standing stalks on the ground right now but very little trash in-between rows, due to the chopper taking the stalks and all. My question is should I rip the ground this fall, then run through it with a field cultivator in the spring and risk soil erosion over the winter? Or, do I wait until spring and rip it and cultivate it right before I plant? I am in north-central Indiana.

 Answer: It’s difficult to give you a straight-out answer, without seeing your ground, so here are a few considerations for you to evaluate. First, are your soils able to handle spring ripping or chiseling?  Where I’m based we can do primary tillage in the spring, because our soils contain a lot of sand.  I don’t know if you’re far enough north in Indiana that your fields can handle the spring tillage, but if they can I’d wait until then.  Another consideration is it sounds like you have some significant soil-health problems and maybe a lot of compaction, too.  I’m concerned you won’t get good water infiltration in your soils during the fall and winter, and you could have a lot of erosion problems.  That would be another reason to do spring, primary tillage. However, on heavy ground I wouldn’t do primary tillage in the spring, because the soil will be too wet and primary tillage will result in you bringing up a lot of clumpy soil, which is going to be a problem when you get ready to plant.  One other thing I’d recommend, if you want to do something this fall, you might consider renting an inline ripper and running it 12-14" deep, and that will leave almost all your residue on the surface.  Running the inline ripper this fall and then coming back in the spring with primary tillage would probably help you address the deep compaction you’re seeing. 

Tillage: To Do or Not To Do Farm Journal’s Field Agronomist Ken Ferrie discusses the proper uses of tillage in Episode 10 of Corn College TV Season 3.  Just because you have chosen tillage in the past does not mean that it is needed every season. The first step is to identify why you are doing it. Start with asking yourself what you’re trying to accomplish and find a procedure that will accomplish that--which may or may not lead to tillage.

How Important Is Tillage When It Comes to Bushels in the Bin? Fixing the seed bed starts with primary tillage tools.

Get the Straight Talk on Tillage As the term vertical tillage becomes more mainstream, clarifying what makes a practice fit this system is key.





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