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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2013-05

Dates Covered: 
March 5, 2013 - March 25, 2013
Steve Prochaska

Sharpen Tank Mixes – Now is the Winter of our Discontent

We would like to first apologize for inadvertently providing what has proved to be false information all winter.  We have been receiving conflicting and changing information on the legality of various Sharpen tank-mixes.  One company in particular told us two weeks ago that they were absolutely certain that they would retain the supplemental labels for mixtures of their products with Sharpen into spring, and then last week we were told that they were retracting those labels.  We were hopeful that there would be labels this spring to allow mixing of Sharpen with products that contain flumioxazin or sulfentrazone but this does not appear to be the case.  The labels for these mixtures that existed last spring were apparently the result of some temporary regulatory glitch or wormhole or warp in the fabric of the universe.  There are still some uncertainties in this situation – there is a supplemental label online for at least one sulfentrazone product that allows mixing with Sharpen but we suspect not for long.  We suggest contacting your local rep or dealer for the most up-to-date information on this as the spring progresses.  Here is the current situation per company involved as far as we know: 

BASF – does not support and has never allowed mixtures of Sharpen with any other PPO herbicides per the Sharpen label.   BASF claims that there is a risk of crop injury from these mixtures, but has never shared data with us that support this.  One reason for their position is undoubtedly the desire to sell their own residual products – Optill and Scepter.  Unfortunately, their residual products do not provide consistently effective control of marestail. 

Valent/Dupont – retracted the labels for mixtures of Sharpen with Valor products and Envive in late 2012 and informed us that they would not have these labels for the spring of 2013.  This also applies to Fierce, which received a label for soybeans about a week ago. 

FMC – retracted the supplemental labels two weeks ago that allowed the mixing of Authority products with Sharpen, and has informed us that these labels will not return for this spring. 

Dow – supplemental label that allows mixing Sonic with Sharpen can still be found online, and Dow informed us several weeks ago that this was an approved mixture per the Sonic label.  We expect this could change since Sonic and Authority First are the same product. 

Syngenta - supplemental label that allows mixing Prefix with Sharpen can still be found online, and we were informed by at least one Syngenta person several weeks ago that this was an approved mixture per the Prefix label. 

So what is left to mix with Sharpen for residual marestail control if we cannot use flumioxazin or sulfentrazone products?  The most effective stategy based on our research would be to use metribuzin 75DF at 8 to 12 oz/A, or add some to premix products that already contain a low rate of metribuzin.  Premix products that fit here – Canopy/Cloak DF, Matador, Boundary/Ledger.  The lack of marestail control with the BASF residual products can also be fixed by the addition of an effective rate of metribuzin.  

What to do if you are locked into a flumioxazin or sulfentrazone residual product and end up too close to planting to use 2,4-D ester, or need a burndown more reliable on large marestail than glyphosate + 2,4-D?  Options here include Liberty or a mixture of Gramoxone plus 2,4-D ester plus metribuzin.  Liberty can be mixed with any residual herbicide and is generally effective for control of emerged marestail, but should also be applied with metribuzin if possible.  We suggest use of at least 32 oz/A of Liberty, and 36 oz/A if the marestail have much size.  With the exception of early spring, we have not been successful at controlling marestail with Gramoxone treatments unless both metribuzin and 2,4-D are in the mix.  Activity of Liberty and Gramoxone will be optimized by applying in a volume of 20 gpa.  Avoid use of nozzles that produce large droplets.

What the Heck is Pyroxasulfone Anyway?

Fierce was recently approved for use on soybeans, and we have had a few questions about this product, specifically about marestail control.  Fierce could be used in corn last season, and there is information on it in the corn herbicide section of the “Weed Control Guide for Ohio and Indiana”, including ratings (although not on marestail).  There is also information on it in the December 18, 2012 edition of C.O.R.N.  Fierce is a mixture of Valor and pyroxasulfone, a new active ingredient that can be found in various products from several companies.  While pyroxasulfone is from a new class of chemistry, it has the same mode of action and similar spectrum of control as acetamide herbicides – metolachlor, acetochlor, dimethenamid.   

Pyroxasulfone is primarily an annual grass herbicide, but it has substantial activity on a number of broadleaf weeds, including lambsquarters, pigweed, waterhemp, and black nightshade, and somewhat less activity on common ragweed and velvetleaf.  Valor is effective on a number of these weeds but Fierce should be more effective or provide a longer period of residual control compared with Valor, for the control of common ragweed, waterhemp, and Palmer amaranth.  Valor is already effective on many of these broadleaf weeds though, so the addition of pyroxasulfone really brings control of grasses more than anything else.  Pyroxasulfone has very little activity on marestail, so we do not expect Fierce to be more effective than Valor on marestail.  

 Other pyroxasulfone corn products for which the spectrum of residual control is due to pyroxasulone alone include Zidua (BASF - pyroxasulfone) and Anthem (FMC - pyroxasulfone + Cadet).  FMC also markets Anthem ATZ, the premix of pyroxasulfone + Cadet + atrazine, which has activity similar to most atrazine premixes.  Anthem ATZ is labeled for use at rates that provide only early-season control, and should be followed by application of broad-spectrum POST corn herbicides.  

Evaluating Wheat Stand this Spring

According to the National Agricultural Statistics Service, 70% of the winter wheat in Ohio was rated excellent or good condition going into the winter.  The other 29% was rated fair and only 1% fell into the poor category.  What is the winter wheat condition as we enter green-up?  Some areas of Ohio may have experienced heaving this winter (of which late planted wheat is more susceptible).  Other areas of Ohio experienced very wet conditions where wheat may have been drowned out.  

Fields should not be evaluated until completely green from warmer temperatures for at least 10 to 14 days. Stand evaluations will be more accurate when made during weather periods that promote growth.  Yield potential is reduced if tiller numbers fall below 25 per square foot after green up. Pick about 10 to 15 spots in the field and count the number of plants per foot of row. A stand with an average of about 12 plants per foot of row may still result in a good population of head-bearing tillers per acre. For those fields with tillers, 15 tillers per square foot is considered minimum for an economic crop. The number of tillers per square foot is equal to the number of tillers in 19.2 inches of 7 inch wide rows or 14.5 inches of 10 inch wide rows. Our studies have shown that under adequate weather conditions, tillering may compensate for relatively poor initial stand establishment.

Nitrogen Recommendations for Wheat

Soon wheat will be greening-up across the state. Ohio State University recommends applying nitrogen between green-up and Feekes Growth Stage 6 (early stem elongation), which is generally the latter part of April. The potential for nitrogen loss will decrease by waiting to apply closer to Feekes 6; however, since we are at greenup, a common sense approach would recommend applying as soon as field conditions allow application equipment, particularly since days available for field activities may be limited between now and Feekes 6.

We would still recommend the Tri-State guide for N rates in wheat. This system relies on yield potential of a field. As a producer, you can greatly increase or reduce your N rate by changing the value for yield potential. Thus, a realistic yield potential is needed to determine the optimum nitrogen rate.  To select a realistic yield potential, look at wheat yield from the past five years.  Throw out the highest and lowest wheat yield, and average the remaining three wheat yields.  This three-year average should reflect the realistic yield potential.

Once you have selected a value for yield potential, the recommendation may be based on the following equation for mineral soils, which have both 1 to 5% organic matter and adequate drainage:  

N rate = 40 + [1.75 x (yield potential – 50)] 

We do not give any credit for the previous soybean or cover crop, since we do not know if that organic N source will be released soon enough for the wheat crop. The Tri-state recommends that you subtract from the total (spring N) any fall applied N up to 20 lb/A, whether you deduct fall N depends how much risk you are willing to take and your anticipated return of investment from additional N. Based on the equation above and deducting 20 lb from a fall application, we would recommend a spring application of 110 lb N per acre for a yield potential of 100 bu, 90 for 90 bu potential; 70 for a 80 bu potential and 40 lb N per acre for a 60 bu potential.  Nitrogen rate studies at the Northwest Agricultural Research Station have shown the optimum rate varies depending on the year. However, averaged over years, yield data from these studies correspond well with the recommendation equation given above. These studies have also shown that regardless of the year, yields did not increase above a spring rate of 120 lb N per acre. 

Managing the Farm Drainage Outlet Year-Round

The benefits of farm drainage do come with some challenges.  Soluble forms of plant nutrients are able to move with soil drainage water and enter streams, rivers and lakes.  In sufficient concentration, these nutrients can cause harmful algae blooms that interfere with aquatic life and human uses of the fresh water supply.  One technology that can be used to limit the total annual load of soluble plant nutrients exiting farm drainage is controlled drainage.  Controlled drainage involves an in-line structure added to the outlet of a subsurface drainage system.  The structure allows the farm manager to artificially raise the outlet elevation and thus retain water in the field subsurface.  The outlet is not plugged nor is the outlet elevation raised to retain water up to the soil surface.  Controlled drainage structures can be adjusted to incrementally raise the elevation from the bottom of the field main to within 12-24 inches of the soil surface, depending on the time of year.

 Drainage Control Structure

Controlled drainage is flexible and allows for management options year-round.   Farmers need dry soils during planting and other spring field operations, thus the controlled drainage structure would be set to free drainage 30-40 days prior to planting through the completion of spring field operations.  After spring operations are complete, the control structure would be set to conserve/retain water in the subsoil from rainfall to be used during dry periods of the summer, leaving 12-24 inches of drained soil at the surface available for rainfall.  If excess soil water is anticipated or received during the summer, farmers can lower the water level in the field by adjusting the control structure.  As harvest nears, the growing crop may have used all the retained water or farmers may need to return the structure to free drainage to lower the water level in the field.  Following harvest and fall field operations, farmers would raise the outlet elevation to 12-18 inches below the soil surface and hold it there until 30-40 days prior to spring planting.

 Water Table


Ohio data collected by Ohio State University and USDA-ARS shows modest crop yield increases resulting from controlled drainage when rainfall/soil moisture is retained and utilized by corn and soybeans.  Controlled drainage has also been shown to significantly reduce the total annual load of soluble plant nutrients exiting farm drainage, documenting that managing the farm drainage outlet year-round positively contributes to improved water quality from today’s production agriculture.


Fertilizer Math

One of the challenges in making nutrient and fertilizer recommendation is paying close attention to units used in results coming from testing laboratories for analysis services. There is not a single reporting standard. For example, soil test maybe reported as parts per million or pounds per acre.  Manure test may have phosphorus reported as P (elemental P) versus P2O5 (phosphate).

Only fertilizer “Guaranteed analysis” standards are defined in Ohio Revised Code to one reporting unit. The reporting form for of fertilizer is Total N (percent)-available phosphate expressed as P2O5 (percent)-soluble potash expressed as K2O (percent) and listed in that order for the material.

As you review reports, take a few minutes to look closely at the units reported with each measure. If a report form has units you do not recognize, check with the originating lab for an explanation of the units plus conversion equations, so test results and a nutrient recommendation can be converted into matching units. Some common conversions and other fertilizer math are below.

1)      Conversion between PPM (Parts Per Million) and Pounds per acre.



PPM * 2 = pounds per acre

40 PPM * 2 = 80 pounds per acre

Pounds per acre / 2 = PPM

80 pounds per acre / 2 = 40 PPM


2)      Conversion between Elemental Phosphorus (P) and Phosphate (P2O5).



Pounds P * 2.29 = pounds of P2O5

26 pounds P * 2.29 = 60 pounds of P2O5

Pounds of P2O5 * 0.44 = pounds of P

60 Pounds P2O5 * 0.44 = 26 pounds of P


3)      Conversion between Elemental Potassium (K) and Potassium Oxide (K2O).



Pounds K * 1.21 = pounds of K2O

54 pounds K * 1.21 =  65 pounds of K2O

Pounds of K2O * 0.83 = pounds of K

65 pounds K2O * 0.83 =  54 pounds of K


4)      Determining pounds of nutrient in a dry fertilizer source.


Example 100 pounds of material with an analysis of 15-28-15

Pounds of material * (% N/100) = pounds N

100 * 0.15 = 15 pounds N

Pounds of material * (% P2O5/100) = pounds P2O5

100 * 0.28 = 28 pounds P2O5

Pounds of material * (% K2O/100)= pounds of K2O

100 * 0.15 = 15 pounds K2O


5)      Determining pounds of nutrient in a liquid fertilizer source.


Example 3 gallon of 10.4 pound per gallon material with analysis of 0.2-0.6-1.7

Gallons of material * material weight per gallon * (% N/100) = pounds of N

3 * 10.4 * 0.002 = 0.06 pounds N

Gallons of material * material weight per gallon * (% P2O5/100) = pounds of P2O5

3 * 10.4 * 0.006 = 0.19 pounds P2O5

Gallons of material * material weight per gallon * (% K2O/100) = pounds of K2O

3 * 10.4 * 0.017 = 0.53 pounds K2O


6)      Meeting a nutrient recommendation with a fertilizer source.


Example How many pounds of 11-52-0 are needed for 50 pounds of P2O5 recommendation?

Nutrient need in pounds / (% nutrient in analysis/100)= pounds of material

50 / 0.52 = 96 pounds of 11-52-0


Developing a Phosphorus and Potassium Recommendation for Field Crops. [Accessed 3/11/2013]

Mikkelsen, R., Math Anxiety: Fertilizer Calculations.$webcontents/A7D980BC92E6385085257810005806EF/$file/MIkkelsen+Math+Insights_2010_pr9.pdf [Accessed 3/11/2013]

Neilsen, R.L., Fertilizer Reckoning for the Mathematically Challenged. [Accessed 3/11/2013]


Topdressing Wheat with Liquid Swine ManureManure Application to Winter Wheat

Topdressing Wheat with Liquid Swine Manure

Research on applying liquid livestock manure as a spring topdress fertilizer to wheat has been ongoing in Ohio for several years. There is usually a window of time, typically around the last week of March or first week of April, when wheat fields are growing and firm enough to support manure application equipment. 

The key to applying the correct amount of manure to fertilize wheat is to know the manure’s nitrogen content. Most manure tests reveal total nitrogen, ammonia nitrogen and organic nitrogen amounts. The ammonia nitrogen portion is readily available for plant growth. The organic nitrogen portion takes considerably longer to mineralize and generally will not be available when wheat uptakes the majority of its nitrogen in the months of April and May. 

Some manure tests also list a “first year availability” nitrogen amount. This number is basically the ammonia nitrogen portion of the manure plus about half the organic nitrogen portion. Again, for the purpose of fertilizing wheat, the organic portion of the nitrogen should not be considered available in time to impact yields. 

Most deep-pit swine finishing manure will contain between 35 and 45 pounds of ammonia nitrogen per 1,000 gallons. Finishing buildings with bowl waters and other water conservation systems can result in nitrogen amounts towards the upper end of this range. Finishing buildings with fixed nipple waters and surface water occasionally entering the pit can result in nitrogen amounts towards the lower end of this range.  

To capture the most nutrients from manure farmers should consider incorporation. Incorporation can result in less nitrogen loss and can especially reduce the loss of dissolved reactive phosphorus. 

Three years of on-farm wheat topdress results are summarized in Table 1. Each field trial was replicated four times. In each plot, the manure ammonia nitrogen application rate was similar to the nitrogen amount in the urea fertilizer; typically about 100 pounds per acre. The manure was applied using a 4,800 gallon tanker with a Peecon toolbar 13.5 feet in width. This toolbar cuts the soil surface with a straight coulter and a boot applies the manure over the soil opening. Urea was applied using a standard fertilizer applicator. 

Table 1. On-farm Swine Fishing Manure Topdressing of Wheat Results (bu/ac)


Swine manure (surface applied)*

Swine manure (incorporated)


Date of nutrient application





April 7th





April 3rd





March 28th

*Incorporation was performed with a modified Peecan toolbar attached to a 4,800 gallon tanker

 In addition to the Peecon toolbar, OSU Extension as also conducted manure research on wheat using the both the Veenhuizen toolbar and Aerway toolbar. All toolbars cutting through the soil cause some disruption to the growing wheat but side-by-side yield comparisons with convention surface applied fertilizer have rarely shown any difference in yields.   

Some Ohio commercial dragline operators are routinely applying livestock manure to wheat each spring. This practice is gaining acceptance as it’s faster and more efficient than manure application with a tanker. The risk of soil compaction is also reduced. 

Dairy manure has been utilized with on-farm research plots when topdressing wheat. Dairy manure contains far less ammonia nitrogen per 1,000 gallons than swine finishing manure and does not consistently produce wheat yields similar to commercial fertilizer. Research on dairy manure as a topdress to wheat is ongoing and adding 28%UAN to the dairy manure to increase its fertilizer value has produced wheat yields similar to commercial nitrogen. 

When applying livestock manure to wheat it’s recommended to follow the NRCS #633 Waste Utilization Standard to minimize potential environmental impacts. 

Additional on-farm manure topdress of wheat plot results can be obtained by clicking on the on-farm research link on the OSU Extension Agronomics Crops team website at


Corn Flea Beetle and Stewart's Leaf Blight

Being early March, it is time to put out the annual corn flea beetle and Stewart’s leaf blight prediction based on the average temperatures the past three months (Dec, Jan, and Feb.).  The occurrence of Stewart's bacterial disease is totally dependent on the level of bacteria-carrying flea beetle survival over the winter.  Because higher populations of the flea beetle survive during mild winters than during cold winters, the winter temperatures have been used to predict the risk of Stewart's disease.  

The 'flea beetle index' is calculated as the sum of the average temperatures (Fahrenheit) of December, January and February.  We find that all areas of the state except for the north have indexes over 95 suggesting that risk is moderate to severe, while those in the north are still over 90 suggesting more low to moderate risk this coming spring. The locations and the corresponding indexes are: Wooster (OARDC) 94.4, Ashtabula 92.2, Hoytville (Northwest Research Station) 91.6, South Charleston (Western Research Station) 96.3, Jackson 105.2, and Piketon 103.7.  While not as high as last summer (2012), they are much higher than what we saw in 2010 and 2011.


The flea beetle index is:
- Index values less than 90 indicate negligible disease threat,
- 90-95 indicate low to moderate levels,
- 95-100 indicate moderate to severe and
- values over 100 predict severe disease threat.

A question is how prevalent Stewart’s bacterial blight is in our state.  While the warmer temperatures this winter might allow for an increase in corn flea beetle numbers, it doesn’t automatically result in higher incidence of Stewart’s.  The surviving flea beetles need to be carrying the bacterium in order to infect plant in the spring, and in order for them to acquire the bacterium, they needed to feed on diseased plant last season. So, with the level of Stewart’s disease being extremely low during 2012, it is quite possible that beetles, even if they survived due to the mild winter, may not be carrying the bacterium. 

We would recommend that growers scout for flea beetles, especially if they have planted a hybrid that is susceptible to Stewart's disease.  Normally we would recommend that growers wanting to take preventive action against flea beetles apply a commercially applied insecticide seed treatments labeled for flea beetles. However, the realization is that most field corn planted these days, especially all transgenic hybrids, already comes with an insecticide seed treatment applied.   Thus, it is mostly non-transgenic corn that might need to be treated specifically for this concern.  Also, most field corn hybrids are more resistant to wilt than sweet corn. Dent corn hybrids vary greatly in their resistance to the leaf blight stage phase of the disease. All sweet corn varieties are susceptible to wilt in the first leaf stage. A few are resistant by the second leaf stage and many are resistant in the third and fourth leaf stage. Consult your seed supplier for information on resistant varieties and hybrids.


Research Summary of Wheat Underseeded to Red Clover

The following summary of recent research on red clover underseeded into wheat appeared in the Agronomy Journal.

Light and Moisture Competition Effects on Biomass of Red Clover Underseeded To Winter Wheat.  Authors:  Adam Queen, Hugh Earl and William Deen., Univ. of Guelph, Guelph, ON. Agronomy Journal Vol. 101 No. 6, p. 1511-1521

The objective of this study was to assess, under field conditions, the effect of light and soil moisture competition on red clover establishment and end of season dry matter production when underseeded to winter wheat. Nitrogen application rate and row thinning treatments were used to alter wheat canopy light penetration as well as competition for soil moisture. Light penetration was consistently increased by lower N rates and by row thinning. Soil moisture, however, was primarily affected by location and year, and was less and inconsistently affected by N rate and row thinning.

Light penetration through the winter wheat canopy, particularly during the period approximating wheat anthesis, significantly affected end of season red clover dry matter production. Reduced light penetration caused lower red clover dry weights. The effect of reduced light penetration, however, was not as pronounced as the effect of soil moisture. Final red clover dry matter was positively correlated with soil moisture, again particularly during the period around anthesis. Unlike light penetration however, treatments imposed in this study had very small and inconsistent impacts on soil moisture. Variation in soil moisture was largely determined by location and year, which may be related to seasonal differences in precipitation, soil type, or management factors, such as tillage system or wheat cultivar.

Given the apparent role of light and moisture, various management practices could be considered to enhance final red clover dry weight. Adjusting N rates to account for red clover benefits to subsequent crops in a rotation, altered wheat row spacing, or winter wheat variety selection are some of the wheat management options to consider. There was 14.4 % greater wheat yield to a greater  N rate.

Early and timely frost seeding of red clover could also be used to minimize light competition effects, and possibly increase tolerance to drought stress by enhancing red clover root development before onset of moisture stress. Early seeding of red clover however, may increase the risk of mortality caused by frost, so screening for improved cold tolerance is required. 

Spring Weather Outlook

 What  does history say might be in store for the 2013 spring growing season?
Historic data such as big U.S. droughts like the 2012 drought or sunspot peaks suggest a slightly colder and wetter spring in the Ohio Valley including Indiana and Ohio. Those same historic indicators also suggested a slightly warmer and wetter winter along with near normal snowfall. That is exactly how winter came out and what the National Weather Service called for. At the same time our climate models suggest a slightly warmer March to May period with precipitation not far from normal.

The main message this spring growing season is most of our data does not suggest the record wet 2011 or record dry 2012 or the record heat of 2012. Most data suggest closer to either side of normal.

Therefore, the outlook for the spring growing season is for temperatures to go from colder than normal in March and early April to slightly warmer than normal by May. At the same time rainfall will likely be close to or slightly wetter than normal. Originally in winter it looked like spring would be slightly warmer and slightly wetter than normal. The main change is the first half of spring looks continued chilly. There is increased risked of some later freezes this spring especially compared to 2012.

In the shorter-term, after an early week rainfall of 0.25 to 1.00 inches on average in the state of Ohio, it will turn colder than normal again with only some very light precipitation. There will likely be another weak system this weekend with a slightly stronger rain system mid or late next week.



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Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.