Preplant Banding Ammonia & Urea in Corn

A very efficient placement method for rates of nitrogen that can’t be placed at seeding is the preplant band. Despite the popularity of direct or one-pass seeding this is still used in crops where some pre-plant tillage is done – like for corn.

The past few years, more often in dry springs, I have seen stand thinning using this practice. When the corn row falls directly over the N band (be it ammonia or urea), seedlings are injured, stunted and sometimes killed. This leaves a repeating pattern in an angle across the field.

There are some standard guidelines if using this practice:

  • Stand thinning may occur where the seed row intersects the N band. Band N on an angle so that it intersects just a short length of row.  OR if the injection placement can be controlled with accurate GPS guidance positioning technology, split with the future corn row.  Six inch separation should be sufficient.
  • Place the nitrogen deep. Banding at 3” depth may be sufficient for slot closure and N retention in the soil – but this will only be an inch or so below the seed. The original guideline calls for 4” vertical separation of injection point and seed.
  • The toxicity will be worse under dry conditions and on sandier soils.
  • Waiting a certain period of time offers only a slight increase in safety.  Injury can still occur even if planting is delayed for a considerable period of time.
  • Increasing plant populations to account for such thinning will not eliminate the appearance of gaps in the row.

Figure 1 is of corn thinning over a preplant urea band.


Figure 1: Corn thinning over a preplant urea band (Photo by John Heard, Manitoba Agriculture)

Figure 2 is of corn seedling based on their proximity in intersecting the shallow placed preplant ammonia band.


Figure 2: Impact of shallow placed preplant ammonia band on corn seedlings (Photo by John Heard, Manitoba Agriculture)

Submitted by: John Heard, Crop Nutrition Specialist, Manitoba Agriculture

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Safe Liquid Fertilizer Rates for Corn

Much of Manitoba’s corn receives liquid phosphorus as a starter in the seedrow.  But we cannot apply sufficient amounts with the seed to meet full crop removal (about 44 lb P2O5/ac for a 100 bu/ac crop).  The safe amount of seed placed fertilizer depends upon soil type, moisture, row spacing and seed furrow opening.  Ontario guidelines base the safe rates of fertilizer on N and K content of the starter fertilizer.  For 30 inch rows no more than 10 lb N/ac should be seedplaced – enough to provide 34 lb P2O5/ac of 10-34-0 liquid fertilizer or 8.5 US gal per acre.  But based on South Dakota  studies such rates could cause stand thinning of 4-9% depending on soil moisture and texture. Most farmers will not be pushing starter rates this high as they should have the bulk of their P needs met through a safer placement strategy.

More on these safe rates of fertilizer is posted on Manitoba Agriculture’s website at:,safe-rates-of-seed-placed-phosphorus-for-manitoba–narrow-row-and-row-crops.html

Submitted by: John Heard, Crop Nutrition Specialist, Manitoba Agriculture


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Safe Rates of Seed Placed Fertilizer – Cereals & Canola

A reminder that if seedbeds turn dry, the safety margin shrinks when applying seed placed fertilizer.  Seedburn can result from ammonia toxicity and/or salt content of fertilizers.

For nitrogen, our Soil Fertility Guide provided safe guidelines for seed placed urea on cereals and canola across a range of soil types and seed-fertilizer configurations.  With the increased popularity of narrow seed and fertilizer spreads with disk drills, the safe rates are reduced.  For example, safe urea rates for cereals vary from 10 to 25 lb N/ac going from sand to clay soil using disk openers on 6” row spacing.  These guidelines are for moist soil and should be reduced by 50% if seedbed moisture is lower when weather is hot and windy.

The safe rates of seed placed phosphorus depends on the crop, with cereals being quite tolerant compared to soybeans, dry beans and canola.  With a disk drill as described above, cereals can tolerate 50 to 60 lb P2O5/ac as mono ammonium phosphate while rates would be 20 lbs/ac for canola and less for beans.   If there greater seedbed utilization (i.e. narrower rows or a wider seedrow with less fertilizer concentration) rates could be more liberal.

More on these safe rates of fertilizer is posted on Manitoba Agriculture’s website at:,safe-rates-of-seed-placed-phosphorus-for-manitoba–narrow-row-and-row-crops.html

Submitted by:  John Heard, Crop Nutrition Specialist, Manitoba Agriculture

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Should I Plant my Corn Now, or Wait for Warmer Soils?

Is it better to plant into cold soils realizing the seed is going to sit there until the soil warms up? Or should corn be planted when soil temperatures are warmer and approaching 10°C?

Planting into cold soils.  Early planting is a component of successful corn production in Manitoba, to maximize yield, obtain high quality and low percent kernel moisture at harvest (which will decrease drying costs), and to ensure the crop is mature before fall frosts.

Cooler soil temperatures can delay the crop’s emergence. Wet conditions added to cold soil temperatures can favor soil pathogen development, increasing seedling disease risks in both germinating seeds and young seedlings. When planting early in the season or when the soil is cold, a planting rate 10% higher than the desired final stand should be considered to compensate for possible increased seedling mortality. As well, when planting into cool soils, other seeding management becomes important, such as good seedbed condition (good soil to seed contact) and planting operations (including planting depth).

For more complete information, visit Manitoba Corn Growers website at


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Qn: Where did all the weeds come from in that corn field?

Farmers are usually well advised to “control weeds early and often” in corn fields. Although many of today’s herbicide tolerant crops and herbicides can control weeds at almost any stage, it is early season competition that reduces nitrogen use efficiency. University of Wisconsin researchers compared weed free corn to delayed weed control. Spraying when weeds were 4” and 12” tall, required an additional 20-60 and 65-160 lb nitrogen /ac, respectively, to produce corn yields equal to weed free plots.

In our 2014 Crop Diagnostic School lesson, corn fertilized with 100 lb nitrogen/ac yielded 145 bu/ac with season-long weed control, 15 bu/ac less when spraying 4” tall weeds and 60 bu/ac less when spraying 12” tall weeds (Figure 1). Unsprayed corn yielded 9 bu/ac. Conversely, with no added nitrogen but early and consistent weed control, the corn yielded 95 bu/ac.

John Heard in corn field

Figure 1. Corn to left in background with full, but late, control of weeds suffered extreme nitrogen deficiency.

However, there are warranted exceptions to maintaining all growing vegetation from growing in corn fields. Many corn fields in southern Manitoba are currently seeded with a wheat or oat companion crop (see Figures 2 & 3). These fields tend to be at high risk of wind erosion: sandy textured, following potato or other low residue crops. Cereals seeded at or prior to corn can then establish and produce early season ground cover to minimize soil erosion and sand blasting injury to young corn seedlings.

Figure 2

Figure 2. A nurse crop of wheat emerging in mid-May, ahead of the corn crop in Winkler area.

oats in corn field

Figure 3. A nurse crop of oats emerging in late May, in Carman area corn crop, prior to spraying for removal.

For more information on erosion and cover crops visit MAFRD’s website at:

Answer Submitted by John Heard, Crop Nutrition Specialist, MAFRD


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How to Determine Leaf Stage in Corn

Knowing what leaf stage your corn crop is at is extremely important since post emergent herbicides can only be applied to corn up to the label-specified leaf stage. Therefore both farmers and agronomists need to accurately stage corn plants. Herbicide labels often refer to plant height, crop growth stage (leaves or collars), or both when discussing corn growth stage limits for the application of postemergence herbicides. Below is a review of some common methods for determining growth stage. It is important to know which method the herbicide manufacturer is using to indicate correct herbicide application timing. For each method, the stage of the corn plant in Figure 1 will be determined.

Corn Plant Staging

Figure 1: Corn Plant Staging


Corn Height Method.  To determine corn plant height, measure from the soil surface to the highest point of the arch of the uppermost leaf whose tip is pointing down.  Don’t measure to the “highest point” on the plant, which is often the tip of the next emerging leaf above.  Refer to Figure 1 on how to correctly determine the height of a corn plant.

Both environmental and management conditions can have a great impact on the height of a corn plant. In cool, wet springs, corn often grows more slowly from a height standpoint but it is still advancing physiologically. A delayed seeding date, differences in tillage, and differences in soil type can also have a pronounced effect on plant height but relatively little effect on the stage of vegetative development. Hybrid can also have an effect on plant height as shorter-season hybrids tend to produce shorter plants. Because corn height varies a great deal due to growing and crop management conditions, it is not the most accurate way to stage corn plants.

Leaf Over Method.  The leaf over method is a common way of measuring leaf number. The leaf over method counts the number of leaves, starting from the lowest one (the coleoptile leaf which has a rounded tip) up to the last leaf that is arched over (tip is pointing down). Do not count leaves younger (inside) than this one, even though they are present in the whorl. In Figure 1, the corn plant would be at the 4 leaf stage.

Leaf Collar Method (V-stage).  The leaf collar method is generally the easiest to use. It also relates better to the physiological stage of the plant and thus to the effects of herbicides. Staging by the leaf collar method is done by counting the number of leaves with visible collars, beginning with the lowermost, short, rounded-tip true leaf and ending with the uppermost leaf with a visible leaf collar . Collars are not visible until the leaves are developed enough to emerge from the whorl. In Figure 1, the corn plant would be at 3 leaf stage (V3).

Staging Corn with Severe Leaf Damage.  Dead leaf tissue will not resurrect itself and will eventually slough off as the plants continue to grow. The question is whether the leaf stage of a recovered plant begins anew with the healthy leaves or whether the dead leaves (which may no longer be visible) should be counted. In other words, should a 3-leaf plant that has lost 2 leaves to frost injury now be considered a 1-leaf plant?

The simple answer is: If corn was a 3-leaf plant prior to the frost, physiologically it still is a 3-leaf corn plant after the frost, no matter how many lower leaves are damaged, dead, or otherwise missing.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD

For additional information on how a corn plant develops, please visit MAFRD’s website at
For the Guide to Crop Protection:
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Can recent cold temperatures & snow impact corn emergence?

Cold temperatures, combined with excessive rainfall in some areas and even snowfall, has created conditions not ideal for the germination and emergence of corn planted recently in Manitoba. Research has shown that temperatures at or below 10°C are most damaging to the germination and emergence process, especially if the cold temperatures persist long after planting.

What is Imbibitional Chilling Injury? Firstly, imbibition is the process by which seeds absorb water for the initiation of germination. In corn, kernels must absorb (imbibe) about 30 % of their weight in water before germination begins (by comparison, soybeans must imbibe about 50 % of their weight in water).

Imbibitional chilling injury may result when water colder than 10°C is imbibed, and effects can be particularly severe in situations where seeds were planted into cool soils (10°C or colder), combined with cold rain or melting snow after planting (the most critical time for imbibition is within 24 hours of planting). The absorption of cold water can disrupt the reorganization of cells during rehydration and can result in the loss of seed vigor or seed death.  Note: A cold, heavy rain after planting seems to increase the chances of imbibitional injury, probably because it overwhelms the ability of the soil to warm the water before it reaches the seed (Source: Joel Ransom, NDSU). 

Symptoms of imbibitional chilling injury include swollen kernels that swell but fail to exhibit further signs of germination or arrested growth of the radicle root and/or coleoptile following the initiation of the germination process.

Instances of non-imbibitional chilling injury following germination during the emergence process can also occur, often causing stunting or death of the seminal root system, deformed elongation of the mesocotyl (the so-called “corkscrew” symptom) and either delayed emergence or complete failure of emergence (i.e., leafing out underground). This type of chilling injury is more closely related to physical damage to the outer cell tissues that literally cause death of the plant part or inhibit further elongation of the affected area. Thus, chilling injury to only part of the circumference of the mesocotyl results in the “corkscrew” symptom as the undamaged sections of the mesocotyl continue to elongate.

The Result of Cold Injury? If germination is impacted, poor stands could result impacting yield potential.  Plants that also develop from injured seedlings may be stunted and develop more slowly than normal plants.  This can result in unevenness in the growth stages of plants within the field.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD 

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Assessing Spring Frost Damage after Corn Emergence

Although there isn’t many acres of emerged corn in Manitoba, some corn has emerged and was recently impacted by the weekend’s frost events.

Corn in the V5 stage (5 leaves with collars showing) or less will recover from light frosts because the growing point is still below the soil surface.  Symptoms of frost damage will start to show up about 1 to 2 days after a frost. Symptoms are water soaked leaves (see Figure 1) that eventually turn brown and necrotic. Frost will often kill young corn leaves but plants, even with extensive leaf damage, will likely recover if the growing point was not injured. The death of leaf tissue above the growing point has only a small effect on corn growth and yield at early stages of development.

While extremely rare, if air temperatures drop to temperatures of -2°C or less for more than a few hours, the growing point region of a young corn plant can be injured or killed even if it is still below the soil surface.

frosted corn 2009

Figure 1: Frost Damaged Corn. Photo by Pam de Rocquigny (2009)

To assess corn plants, look at the growing point approximately 3 to 5 days after the frost occurred.  By this time, surviving corn plants should be showing new leaf tissue expanding from the whorls (see Figure 2).  Note, it is not unusual for the new leaves to get ‘caught up’ in the dead leaf tissue.  You can also check the growing point, which can be found by pulling up the entire corn plant, including roots, and splitting the entire plant lengthwise. If the growing point is white or creamy in appearance injury didn’t occur.  However, damaged tissue in the growing point region will be discolored and soft or “water-soaked”. There will also be lack of new regrowth from the whorl.

Frosted Corn CDS 2009 Day 6 (2)

Figure 1: Frost Damaged Corn, 6 Days after Frost Event. Photo by Pam de Rocquigny (2009)

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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Historical Seeding in Progress in Manitoba – First Week of May

Producers who participate in AgriInsurance provides seeding date information to Manitoba Agricultural Services Corporation (MASC).  This dataset provides us a historical perspective of when seeding has taken place in the past.  Seeding date data information is broken down into a week:month format, i.e. 1:05 is Week 1 in the 5th Month (May).  So 2:05 is Week 2 in May, and so on.

Each week is then categorized dependent on the day of the week in which the month starts.  So if Week 1 starts on a Sunday, there will be 7 days of seeding captured in Week 1.  However, if Week 1 starts on Friday (like we have in 2015), there are 9 days captured in Week 1.  Confused yet?  Essentially, each year will have a different number of days captured in each weekly timeframe, varying from 5 days up to 12 days.  However, the data still provides good reference points to seeding progress in Manitoba.

In Table 1, cumulative seeding progress to the end of Week 1 in May for six crop types is provided.  The last five year (2009-2013) average cumulative seeding progress is noted, along with what was seeded in the same timeframe in 2014.   Please note that data is for final insured crop in the ground.

Table 1:  Seeding progress (%) in Manitoba by end of Week 1 in May (1:05).

End of Week 1 May Seeding Progress

Based on the May 11th Manitoba Crop Report, overall seeding progress is estimated at 55% complete.  There isn’t a provincial breakdown provided of seeding progress by crop type, but in looking at each region, seeding of spring cereals is ahead of the 5-year average of 2009-2013, and well ahead of 2014!

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD 

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Confused about Fluency? Read on…

Submitted by Jeanette Gaulthier, MAFRD Pesticide Use Specialist and Holly Derksen, MAFRD Field Crop Pathologist

The PMRA requires the use of Fluency Agent as the seed flow lubricant when planting corn or soybean treated with a neonicotinoid insecticide (a list of products is included in the link below). Fluency Agent produces 65 percent less dust than talc or graphite and may significantly reduce the risk of neonicotinoid exposure to bees and other pollinators.

This requirement only applies to treated corn and soybean seeded using vacuum planters. Although not required, Fluency Agent can be used in all types of planters.

As with anything new, producers using Fluency Agent for the first may have a bit of a learning curve before things run smoothly. Nathan Klassen, Seed Growth Specialist, with Bayer CropScience offers these tips to avoid hiccups:

  1. Give it a mix. Add Fluency Agent to the seed tote or planter box and give it a quick stir with a stick or gloved hand – 30 seconds is more than enough. A thorough mix before the first run of the year with your planter helps lubricate the equipment; a quick mix when refilling the planter during your subsequent fills ensures the product is mixed within the seeds.


  1. When it comes to Fluency Agent, less is more.   A 1/8 cup treats 1x 50 lb bag of seed or a 400 gram container treats 1 seed tote (50 bags). Don’t over apply the product; there is no advantage to adding extra to your seeds before going into the planter.

Fluency Agent is available from your corn and soybean seed dealers as well as select equipment dealerships.

Use of Fluency Agent is just one way to reduce the risk of neonicotinoid exposure to bees. Visit the Manitoba Corn Growers Association website for a full list of Best Management Practices:


Pest Management Regulatory Agency Requirement when using Treated Corn/Soybean Seed:

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