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Farming in Vermont

Corn Crop Considerations after Record Rainfall

Posted: June 1st, 2011 by djhudson

Corn Crop Considerations after Record Rainfall

by Daniel Hudson, Agronomist, UVM Extension

Every year offers particular challenges to corn growers.  In much of New England, the challenges of the 2011 planting season are tied to excessive precipitation; some areas received seven inches of rain in less than 36 hours!  Here are a few questions that farmers have in these circumstances, followed by brief answers.

1. How long can corn seed or seedlings be under water and still survive?

Seedlings need oxygen, but they can survive for a short period of time under water.  Exactly how long they can survive is somewhat temperature dependent.  The rates of the chemical reactions happening in plants are heavily influenced by temperature: the warmer it is, the faster the reactions are happening.  In general, the faster the chemical reactions, the higher the demand for oxygen, especially in the root zone.  Plants that are under water have very little access to oxygen, and whatever oxygen is there is quickly depleted.  Thus, it is not surprising that plants cannot tolerate being submerged for nearly as long in warm weather as they can in cooler weather.  During warm weather (above 77 ⁰F) corn seedlings younger than the six-leaf stage can die after 24 hours of being submerged.  If it is cool, they can survive for up to four days.  If the seeds are just germinating, the same principle applies, but the amount of time they can survive is not as precisely known, and it can vary with variety.  If you want to know whether your seedlings have survived or if they are “dead on their feet,” dig up some seedlings and cut lengthwise through the seedling and look at the growing point (which remains on the underground portion of the plant until the five- or six-leaf stage).  If it is brown or tan and mushy, the seedling is as good as dead.  The same applies to newly germinating seed.  A healthy germinating seed will have a firm cream-colored root and shoot.


Elmore, R. and L. Abendroth. 2007.   Corn Survival in Flooded or Saturated Fields. Iowa State University Extension.  Online: http://www.ipm.iastate.edu/ipm/icm/2007/4-30/flooded.html

2. What is the best way to decide whether to replant a field due to damage from hail or flooding?

This is an excellent question, but the answer is longer than I have space for here.  Instead, I will refer you to the article Corn Replant / Late-Plant Decisions in Wisconsin by University of Wisconsin agronomist Joe Lauer.   Granted, Wisconsin has a different environment than New England, but it is a northern tier state that shares many similarities with our climate, and many of the same challenges.  I know that it is late in the growing season, but my general observation is that it is very tempting for farmers to replant partially damaged stands, even in cases where it is not economically beneficial, so readingthe article referenced above might be a very profitable use of time.

3. My corn was 3” tall when the hail came, and the tops are basically gone on many of the plants.  Should I replant?

Corn at this stage can easily recover from complete defoliation.  The growing point (where the leaves and ear of the plant initiate their growth) of a corn seedling remains below the ground until the plant has five or six leaves with collars.  Replanting fields that were defoliated prior to that stage is not profitable unless there are some other unusual factors.

Those with concerns about hail damage and questions about replanting can also find excellent information in the article Growing Points of Interest by Purdue agronomist Bob Nielsen.

4. We got seven inches of rain in 36 hours. How much nitrogen did I lose?

Soils have been warm enough that much of the ammonium (NH4+) has already converted to nitrate (NO3).  Nitrate moves with water, regardless of whether it is from manure, or synthetic fertilizer. In sandy soils, one inch of rain can move nitrate six inches downward! One comforting fact in much of the affected area is that the rain came down so heavily that most of it left the fields flowing over the surface rather than moving through the soil profile.  More coarse textured soils often permit more water to move through the soil profile, depending on what is under them and on the slope of the field.  While there is some comfort in knowing that we did not lose as much nitrate from the soil as we would have if the rain came over the course of three days, it still leaves a lot open to the imagination.  If you have any question about whether you will need to sidedress more nitrogen than you planned, I strongly encourage you to take pre-sidedress nitrate tests (PSNT) from at least a couple of fields, just so you have an idea of how much nitrate is there.  These tests are not perfect, but they are much better than operating with no information whatsoever.   Information about how to take the samples and interpret the results can be found at: http://pss.uvm.edu/vtcrops/?Page=articles/PSNTTest.html.


Warncke, D. and C. Laboski.  2004.  Field Crop Advisory Team Alert: Nitrogen losses

due to excessive rainfall.  Michigan State University Extension.  Online: http://www.ipm.msu.edu/catfield/fc5-27-04Flood.pdf


5. Will all of this rain make my soil-applied herbicides ineffective or cause injury to my corn?

It is possible that with some products, the excessive rains we received could reduce efficacy or cause some injury.  Included among these products are Prowl, Prowl H2O, and Pendimax, where injury is more likely on sandier soils.  Basis, Resolve, and no doubt other herbicides can also cause some crop damage and/or have reduced weed control efficacy in saturated soils.  Check product labels for conditions under which herbicide injury or reduced efficacy may occur.

6. Should I re-apply my soil-applied herbicides?

Even if the corn still is not emerged or if you need to replant, the answer is not to re-apply more of the same product.  Just to be clear, the reasons for this are not environmental, but due to the fact that much of the product is probably still present and higher rates could injure your crop.  In many cases, weed control will still be excellent.  The best thing to do in this case is to wait and control weeds that appear later with cultivation and/or post-emergence herbicide applications, which means it will be necessary to scout fields of concern for weed issues.

If you do replant acres to which products such as Prowl or Pendimax were applied, do not re-till the soil.  In this case, try to disturb the soil as little as possible during the planting process, and try to plant the corn two inches deep (or even a bit deeper) to get it below the herbicide in surface soil in order to avoid crop injury.  Given how much rain some areas received, even if this is done, it seems to me that there is some risk of crop injury due to the herbicide moving down further in the soil than it usually would.

References (for questions 5 and 6):

Kells, J. 2004.  Field Crop Advisory Team Alert: Excessive rain and soil-applied corn herbicides.  Michigan State University Extension.  Online:  http://www.ipm.msu.edu/catfield/fc5-27-04Flood.pdf

Schirmacher, K., and J. Kells, 2004.  Field Crop Advisory Team Alert: Herbicide considerations when replanting flooded corn.  Michigan State University Extension.  Online:  http://www.ipm.msu.edu/catfield/fc5-27-04Flood.pdf


Many farmers are way behind where they would like to be, relative to planting and haylage harvest.  Being tired, frustrated, discouraged, and/or in a hurry generally increases the risk for farming-related injuries.  Keep perspective, and be safe!

If you do have particular questions or concerns about your crops and would like an objective opinion, do not hesitate to contact me or your local extension agronomist.

Daniel Hudson can be reached at daniel.hudson@uvm.edu or by calling 802-535-7922.

It is not the intention of the author or University of Vermont Extension to endorse or promote the use of any product over another.


Concerns about Smooth Bedstraw

Posted: May 20th, 2011 by djhudson

There has been more than one farmer interested in learning more about smooth bedstraw this spring.  This unpalatable weed can be very invasive, and it reproduces relatively early.  Some interesting facts that can help you manage this weed include:

  • The seeds are viable even when they are still green
  • The seeds are only viable in the soil for about a year
  • When conditions are wet, the seeds are likely to cling to your equipment and can easily be spread to other fields
  • Weeds in general will encroach on areas where forage plants are not competitive, often due to sub-optimal soil fertility, compaction, or poor species/variety selection.
  • Any herbicide that kills smooth bedstraw will also kill your legumes
  • It has begun to flower

My purpose here is to discuss some alternatives for reducing the presence of this weed in your hay field or pasture, short of starting over altogether.

Smooth bedstraw in a pasture

Organic farmers and others preferring not to use herbicides will have to focus on using harvest management to reduce seed production and also not neglect to discover underlying agronomic issues that allowed the smooth bedstraw to take hold.  These farmers will also need to find ways to re-introduce forage species in places where they have been crowded out by weeds.  To reduce the number of smooth bedstraw seeds produced this year, forage needs to be harvested even before the green seeds are formed on the smooth bedstraw plants.  Harvesting will help, but will not entirely prevent seed production for all plants, because some of the plants will already have viable seeds by the time things dry out enough to harvest, and others may be prostrate enough not to be picked up by harvesting equipment.

If you are not organic and don’t mind losing all of the legumes in your pasture or hay field for a while, you have the option of using herbicides.  Literature from University of Maine Extension suggests that triclopyr-containing herbicides labeled for use on pastures and hay fields, such as Crossbow, or aminopyralid containing herbicides, such as Milestone or Forefront RP, are effective against smooth bedstraw. Applying one of these herbicides prior to seed being produced in the spring and another in August/September should vastly reduce the amount of smooth bedstraw in your stand next year.  If you are only able to make a late-summer or early-fall application, you will still have spring-produced smooth bedstraw seed to contend with next year due to the longevity (about one year) of the seeds produced this year.

Keep in mind, this weed took hold because it had an opportunity.  Now is the time to figure out if it is compaction, poor soil fertility, or some other agronomic problem.  If the problem is not fixed, you can expect smooth bedstraw (or worse) to visit your pasture or hay field again.  If the plants produce seed this year, the problem will almost certainly be present next year.  Please understand that all of the herbicides mentioned above will kill your legumes and many other broadleaf weeds (and other broadleaf plants if the herbicide drifts!).  Pay close attention to harvest restrictions. The aminopyralid herbicides can be persistent and the label says the manure from animals consuming forages from fields to which aminopyralid has been applied should not be spread in areas where broadleaf vegetables will be planted. They also say that a ‘bioassay’ should be conducted prior to trying to re-establish legumes.  One way to do this is to go out in March (or so) and get some soil from the field to which the aminopyralid was applied the previous season.  Bring it inside, and sprinkle some red clover seeds on it, covering them lightly with soil.  Keep the soil moist, at about room temperature, and in a well-lit area so the seeds will germinate, emerge, and begin to develop.   For comparison, the same process should be done using soil from a field not sprayed with the aminopyralid herbicide. If both batches of clover seedlings seem to get going well enough, consider frost-seeding or no-tilling clover into the existing grasses to increase the legume content of the stand and to fill in the gaps. I only suggest using this type of “soil bioassay” because the label does specify what kind of ‘bio-assay’ they have in mind; this would seem to fulfill the letter (if not the spirit) of what they are suggesting.

To give you an idea of the cost of these herbicides one local farm service provider recently indicated that Crossbow was $53/gallon and Forefront was $64.50/gallon.  The labels suggest Crossbow be applied at 2 quarts per acre, and Forefront at 1.5 – 2.6 pints per acre. Always read and follow the label and take special note of harvest/grazing restrictions, which are from 0 to 14 days, depending on the product, harvest method, and class of livestock to which it will be fed.  The labels for the products discussed can be found at:
Milestone: http://www.cdms.net/LDat/ld77N009.pdf

It is not the intention of the author or University of Vermont Extension to endorse or promote the use of any product over another.


Seiter, Stefan, 2003.  Managing Smooth Bedstraw in Forage Crops.  University of New Hampshire Extension. Online: http://ceinfo.unh.edu/Pubs/AgPubs/bdstrw.pdf.

Kersbergen, Richard, 2008. Bulletin #2778: Controlling Smooth Bedstraw in Hayfields and Pastures.  University of Maine Extension.  Online: http://umaine.edu/publications/2278e/

Did the Over-Seeded Red Clover ‘Catch’?

Posted: May 19th, 2011 by djhudson

Seedlings need light, moisture, and nutrients to survive in the field.  In most early-spring pasture over-seeding situations, the moisture and nutrients are probably not the major limitation to success.  With rapidly growing perennial pasture plants, light often limits success, so it is important to monitor how the seedlings are doing.  Periodically check several locations in the over-seeded area.  Note the stage of development of the seedlings and the amount of competition they currently have; using a bit of mental extrapolation, keep in mind how much competition they will have next week or two weeks from now.

Initially, the seed has enough energy stored to germinate, put down a few roots, and expand the first leaves (cotyledons).  With a little encouragement (light), the seedling can progress to maturity, but it needs light.  Most farmers don’t have the luxury of focusing their forage harvest strategy on how best to get their red clover to survive, but where harvest manipulation is an option, it can help.  Every dairyman and most grass farmers want to take their first cutting early than they are usually able to, but if you need one more reason to do so, understand that the sooner the clover gets more intense light, the more likely it is to become an adult plant, contributing to forage quality, forage quality, and soil fertility.  There comes a time when there is so much competition that the red clover seedling will die from the lack of sunlight.
The picture below shows the stage of the clover seedlings at Kinship Farm in South Kirby.  The ‘unifoliate’ stage will be followed by the ‘first trifoliate’ stage.  A ‘trifoliate’ is the typical three-leafed clover that we are used to seeing.









Healthy dandelion plants, dense ladino clover, and Kentucky bluegrass seem to provide so much competition that it seems doubtful that the clover seedlings will survive in areas where these plants are thriving, but only time will tell.


Seedling Progress in Overseeded Pastures

Posted: May 2nd, 2011 by djhudson

Several Vermont farmers are working with UVM Extension on pasture and hay field renovation projects.  The snow stayed longer than usual this spring and in many cases the ground was not frozen underneath, so opportunities for true “frost-seeding” were sparse.  That said, overseeding can still work, but it requires more careful managment, and there are no guarantees.


The pictures below are from a pasture that was overseeded on April 15 with red clover and annual ryegrass.  The clover seedlings are at the dicotyledon stage and the ryegrass  is at the one shoot stage.  The established perennial pasture grasses and legumes  are putting on some top-growth, but at this stage are investing in root development.  Once the plant shifts its priority to increasing the amount of top-growth, we will need to pay careful attention to the stage and condition of the seedlings and manage the grass canopy accordingly.  The seedlings at this stage seem very tender, and it is not clear how much traffic they will tolerate.  Next week, I may flash-graze a section of my pasture that has been over-seeded, just to see how that affects the establishment of the over-seeded forages.



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