Apr 17, 2014
Home| Tools| Events| Blogs| Discussions| Sign UpLogin


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 TestPlots@FarmJournal.com, and we’ll respond on this blog to provide an interactive dialogue.

Can I expect a corn yield boost if I use Y drop attachments to apply N prior to tassel?

Apr 15, 2014

Question: I am an agronomist in northeast Ohio and have a customer that is interested in exploring an avenue to apply nitrogen (N) late in his corn crop.  He is currently applying 40 lbs. of N at planting in a 2X2 through the planter.  At spike he applies 100 lbs. of AMS.  Then he side dresses 220 lbs. of anhydrous ammonia around V-4.  He is looking to set his sprayer up with the Y drop fertilizer attachments and apply up to 45 lbs. of N prior to tassel.  He asked me to ask you if you had any experience with Y drop or any suggestions.   

Answer:  We used the Y drop for the first time last year here in Illinois. We compared it to side dressing versus direct dribbling, and the Y drop did as well as the side dressing with the coulter. It did better than just the dribble. In your customer’s case, an additional application of N is only going to help him if he’s running out of N later in the season. You need to monitor that with visual inspections of the field and tissue testing. If he’s not having an N deficiency, it may not be worth doing as it won’t improve yield any.  If he pulls his side-rate application down and loses that N later, he might be able to make some money by being more efficient.  Breaking up his applications into a number of applications—but not applying more N—might help him make some yield headway. Adding N applications will only improve yields if he’s losing N late in the season.  The last window of opportunity where you can really make a difference is making an N application about the week before tassel.  Going later than that probably won’t be beneficial as you’re not likely to get the N up into the plant quickly enough to impact yield.

What Are the Nitrogen Requirements for Corn Early in the Season?

Here's how to maintain healthy nitrogen levels, starting with emergence.


Saturated Soils Put Pressure on Nitrogen Applications

Record snowfall this winter is causing farmers to evaluate the potential impact excess moisture may have on the nitrogen applications they made last fall.

 

Nitrogen Advice

Shifting nitrogen fertilizer applications to later in the growing season pays off in higher yield.

 

 

Put A Stop to Palmer Amaranth Pigweed

Apr 09, 2014

Palmer amaranth is a weed species that must be thoughtfully and carefully managed. Simply attempting to control Palmer amaranth often leads to ineffective herbicide applications, substantial crop yield loss, and increased weed infestations, says a University of Illinois Extension weed scientist.

"If ignored or otherwise not effectively managed, Palmer amaranth can reduce corn and soybean yield to nearly zero," says Aaron Hager. "The threat of Palmer amaranth during the 2014 growing season is very real across a large portion of Illinois."

The U of I weed science program has developed recommendations for management of Palmer amaranth in agronomic crops. These recommendations were developed in accordance with the unique growth characteristics of this weed species. The goals of the recommendations are twofold: to reduce the potential for Palmer amaranth to negatively impact crop yield, and to reduce Palmer amaranth seed production, which ultimately augments the soil seed bank and perpetuates the species. 

Three general principles of Palmer amaranth management include:

  • Prevention is preferable to eradication. Prevention refers to utilizing tactics that prevent weed seed introduction and weed seed production.  "Palmer amaranth is not native to Illinois so any population discovered in the state originated from seed that somehow was moved into the state," Hager says. "The myriad of ways in which Palmer amaranth seeds can be transported, however, makes preventing seed introduction extremely challenging. Once Palmer amaranth populations become established, utilizing any and all tactics to prevent seed production becomes of paramount importance."
  • Expect treatment to be costly. It is not uncommon for annual herbicide costs to at least double once Palmer amaranth becomes established. There are simply no soil- or foliar-applied herbicides that will provide sufficient control of Palmer amaranth throughout the entire growing season. 
  • Control of Palmer amaranth should not be less than 100 percent. "In other words, the threshold for this invasive and extremely competitive species is zero," the researcher says. "Female Palmer amaranth plants produce tremendous amounts of seed, and in less than five years a few surviving plants can produce enough seed to completely shift the weed spectrum in any particular field."

 

Recommendations based on Palmer amaranth germination and emergence characteristics include:

  • Be certain to control all emerged Palmer amaranth plants before planting corn or soybean. Burn-down herbicides or thorough tillage are effective tactics to control emerged Palmer amaranth plants before planting. Keep in mind, however, that glyphosate will not control glyphosate-resistant Palmer amaranth and that growth regulator herbicides (such as 2,4-D or dicamba) are most effective on Palmer amaranth plants less than 4 inches tall.  If pre-plant scouting (which is especially important prior to planting soybean) reveals Palmer amaranth plants taller than 4 inches, consider using tillage instead of herbicides to control the plants.

 

  • Apply a full rate (based on label recommendations for soil texture and organic matter content) of an effective soil residual herbicide no sooner than seven days prior to planting and no more than three days after planting. Many soil residual herbicides that are effective for controlling waterhemp are also effective for controlling Palmer amaranth. In soybeans, products containing sulfentrazone (Authority) or flumioxazin (Valor) have provided effective control of Palmer amaranth. Application rates of products containing these active ingredients should provide a minimum of 0.25 lb ai/acre sulfentrazone or 0.063–0.095 lb ai/acre flumioxazin.

Hager says growers should not rely solely on glyphosate to control Palmer amaranth. "Molecular assays have indicated that resistance to glyphosate appears to be relatively common among recently identified Palmer amaranth populations in Illinois," he explained.

Recommendations based on Palmer amaranth growth rate include:

  • Begin scouting fields within 14 to 21 days after crop emergence. "We recommend this interval even for fields previously treated with a soil residual herbicide applied close to planting," he explained.
  • Foliar-applied herbicides must be applied before Palmer amaranth plants exceed 4 inches in height. The effectiveness of most foliar-applied herbicides dramatically decreases when Palmer amaranth plants are taller than 4 inches.  Postemergence herbicides that demonstrate control or suppression of Palmer amaranth include synthetic auxin herbicides (dicamba, 2,4-D), diphenylethers (acifluorfen, lactofen, fomesafen), glufosinate, glyphosate, and HPPD inhibitors (mesotrione, tembotrione, topramezone). 
  • Consider including a soil residual herbicide during the application of the foliar-applied herbicide. A soil residual herbicide applied with the foliar-applied herbicide can help control additional Palmer amaranth emergence and allow the crop to gain a competitive advantage over later-emerging weeds.
  • Fields should be scouted 7 to 14 days after application of the foliar-applied herbicide to determine herbicide effectiveness; if the soil residual herbicide included with the post application is providing effective control; and if additional Palmer amaranth plants have emerged. 

"If scouting reveals additional Palmer amaranth plants have emerged, make a second application of a foliar-applied herbicide before Palmer amaranth plants are 4 inches tall," Hager says.

In regard to Palmer amaranth seed production, Hager says research has demonstrated that female Palmer amaranth plants are capable of producing numbers of seed comparable to that of waterhemp (several hundred thousand to over one million). "Physically remove any remaining Palmer amaranth plants before the plants reach the reproductive growth stage," he advises. "Plants should be severed at or below the soil surface and carried out of the field. Severed plants can root at the stem if left on the soil surface, and plants can regenerate from stems severed above the soil surface."

 

Calibrate equipment to adjust for variable soybean seed size

Apr 08, 2014

Reports of larger-than-normal soybean seed are fueling some concerns about planting this spring. While smooth planting with larger soybean seed may not be a snap, it shouldn’t be a problem, either, according to Seth Naeve, University of Minnesota Extension soybean specialist.

"It's not nearly as big of a deal as in years past because seed is now generally sold by the number (140,000 seeds) instead of by the weight," says Naeve.  "Farmers will just need to be aware that they will have larger volumes (and weight) in seed if seed size is large."

He adds: "Some producers even prefer larger seed. A larger seed does have more stored energy and mineral recourses for the emerging soybean plant.  However, the larger cotyledons can be more difficult to force up through the soil.  So, soil type does impact whether large or small seeded soybeans emerge better, but overall it's a wash."

Seed size is greatly affected by the environment, but there is little interaction with variety, he notes.  So, when seed size increases, it’s usually across soybean lines (of the same maturity).  

He adds that very large seed is usually the result of poor conditions during seed-set, paired with much better conditions during late seed-fill.

While there are reports of larger-than-normal seed size in some parts of the country, Naeve points out that the 2013 U.S. Soybean Export Council survey indicates that last year Iowa farmers produced average to below-average sized seed except in the northwest corner of the state, where seed size was much larger than normal.

As in any year, the important thing is to calibrate your soybean planter or drill as you head to the field, and remember to recalibrate between varieties to make sure you plant the intended amount of seed. If you have any concerns, contact your seed supplier and equipment dealer about setting your equipment to handle this year’s seed sizes.

 

Four Tips to Give Soybeans a Good Start

The time you spend monitoring soil moisture, planting depth, seed-to-soil contact and planting equipment calibration will be rewarded with uniform and rapid soybean emergence.

 

 

 

Four States Confirm Western Corn Rootworm Resistance Problems

Apr 03, 2014

University entomologists report that field-based western corn rootworm (CRW) resistance to the Bt toxin Cry3Bb1 is now found in four states, with confirmation recently announced in Nebraska. Resistance has been confirmed by researchers previously in Illinois, Iowa and Minnesota. Scientists in Colorado, Kansas, Missouri, New York, South Dakota and Wisconsin also are reporting significant damage in fields planted to corn hybrids containing the single Bt toxin. However, researchers in those states have not made a final determination that resistance is there. While Cry3Bb1 has been suspect in most of the CRW resistance cases, the practice of continuous corn and the repeated use of a single toxin are putting increased stress on all of the Bt toxins currently available. In 2013, Aaron Gassmann, an entomologist at Iowa State University, confirmed some cases of western corn rootworm resistance to the mCry3A toxin in that state. Ken Ostlie, University of Minnesota Extension entomologist, is finding similar problems in that state. "We continue to receive reports of Cry3Bb1 performance problem fields, although with VT Triple and VT Triple Pro being phased out, the issue will be masked by Cry34/35Ab1 in SmartStax," he notes. "We've also verified cross resistance with mCry3A at several locations.  We also have had some troubling reports the last two years of performance problems with SmartStax and even Herculex Xtra, but don't have confirmed resistance to Cry34/35Ab1 yet." Most scientists are concerned the resistance issue will continue to worsen if farmers don’t adopt a more comprehensive integrated pest management (IPM) program. Consider these recommendations to reduce your risk in 2014:

1.      Rotate your crops. If you must plant continuous corn, make it a point to rotate fields on a schedule every three to four years.  

2.      If you must grow continuous corn, rotate modes of action, just as you would with herbicides.  Avoid using the same Bt year after year by planting a hybrid with a different Bt trait or multiple Bt traits for rootworm. Alternatively, plant a conventional hybrid with a soil insecticide. The use of a soil insecticide on top of a Bt hybrid is not recommended by most corn entomologists.

"We have shown in our field trials that insecticide on top of a single trait only improves relative root protection if the single trait is starting to fail in the field (i.e. due to resistance evolution)," explains Lance Meinke, University of Nebraska-Lincoln entomologist.   "In this case, root protection improves but selection for resistance to the trait continues, so this is not a good long-term solution to the problem.

"Root protection from single traits that work well does not increase when insecticide is added on top of the trait," he adds.  "Also, we have not seen an increase in root protection when an insecticide is added on top of a pyramid containing Cry34/35Ab1.  So in most cases, we do not recommend using a soil insecticide on top of a pyramid that contains Cry34/35Ab1."    

3.      Scout cornfields for damage this summer and report any problems identified to your state Extension entomologist.

Western Corn Rootworm Bt Resistance Now Includes mCry3A Toxin

The problem has been confirmed in some continuous cornfields in Iowa and likely extends to other Midwest states, an Iowa State University entomologist says.

 

Be on the Lookout for Corn Rootworm Beetles

In appearance, adult western corn rootworms are about 1⁄4"-long with yellow bodies and three black vertical stripes across their backs.

 

Resistance Reality

Western corn rootworm breaks through Bt control.

 

 

 

How do I maximize populations for maximum corn yields?

Mar 24, 2014

Question: It seems to me that the high population talk is a trap by the seed companies.  If they would breed a good flex-eared hybrid so we could plant at 25,000 to 28,000 population, we would be much better off in a year like 2012. Also I am not aiming for 250 bushels when my maximum yield potential is only 200 to 220 bushels. A 45,000 to 60,000 population may be fine for test plots but not for whole farms. How can we afford seed at the high populations?

Answer: You’re right in your thinking.  But you have to intermingle ear type with leaf structure.  So, if we’re trying to conserve water any year in any soil type, we want to reduce populations because they consume less water.  But as soon as you reduce populations, as you’ve noted, you need a good flex ear.  You need a hybrid that will flex and get you back to where you want to be in yield.  You also need to look at leaf structure.  In genetics, there’s what we call three leaf types: upright, pendulum and semi-upright.  You also need to capture at least 96% of the sunlight out there to maximize yield.  So, if you lower the population fewer plants means you need bigger leaves and in a pendulum format. Those leaves need to flop out in the row to capture that sunlight. Then, you need an ear style, a flex ear, that can make up that difference.  When we talk about a 45,000 to 60,000 population we’re talking about a very upright leaf structure that allows the sunlight down inside the canopy so plants capture that sunlight to produce food. And we’re also talking about a very determinate hybrid. So you need to push populations to make yield, because the ears won’t flex as much; they have an upright architecture to let sunlight deep inside the canopy.  If you lower populations with an upright hybrid you could burn up and lose all your water if too much sunlight gets in. If you lower populations with a determinate ear you can give up too much yield because the ear won’t flex to make up that difference.  So, in this format, you’re correct. What if you chose a flexed ear in 25,000 or 28,000 and did it on less population? You’ll need a pendulum leaf structure versus an upright structure so you can capture the sunlight to produce the yield you’re looking for.  You’re going to need to get between 7 bu. and 10 bu. per 1,000 population and not the 5 bu. or 6 bu. that we usually look for. So we’re talking about high populations, determinate ears and upright leaf architecture. We’re also talking about low populations to manage water and flex ears and a very pendulum leaf architecture.  You have to marry both of these two up.  It’s amazing how much yield today we have given up by pushing populations too high for the leaf structure we’ve got.  The problem with flex-eared hybrids is if you push them too hard, they flex both ways. They can flex yields off.  Determinate hybirds, if you don’t push them they won’t yield.  But if you push them they’re more resilient and won’t back up. If you’re going to lower the population you need full flex and you need pendulum leaves—you’re looking for both of these characteristics in the hybrid.

Seed to Success

The first step in variable-rate populations is working with a seed representative to select the right hybrid.

 

Zero In On Population

Improvements in seed corn genetics have resulted in hybrids that perform best when planted in higher populations.

 

Calculate Your Soybean Seeding-Rate Needs

Soybean seed costs have risen, farmers don’t want to plant more seeds than they need for top yields.

 

Log In or Sign Up to comment

COMMENTS

Hot Links & Cool Tools

    •  
    •  
    •  
    •  
    •  
    •  

facebook twitter youtube View More>>
 
 
 
 
The Home Page of Agriculture
© 2014 Farm Journal, Inc. All Rights Reserved|Web site design and development by AmericanEagle.com|Site Map|Privacy Policy|Terms & Conditions