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Ohio State University Extension


C.O.R.N. Newsletter 2008-37

Dates Covered: 
October 28, 2008 - November 4, 2008
Curtis E. Young

Making Fertilizer Comparisons Based Upon Price

Authors: Robert Mullen, David Henry

Careful selection and comparison of fertilizer materials is becoming more important with increasing prices and the number of materials available. The most crucial step in making a fertilizer comparison is converting the prices of different materials to equal units such as price per pound of nitrogen, phosphorus, or potassium. In order to make these conversions, there are a few pieces of information about each product that are needed.

* Cost per unit weight (for solids) or volume (for liquids)
* Material nutrient analysis (N-P-K)
* Density or specific gravity (for liquids)

Since materials have different material analysis, comparing the price per ton of two different fertilizers does not indicate which is the most economical. In order to compare two different fertilizers they must be placed on an even playing field to make a meaningful comparison. If the materials could be expressed in price per pound of the nutrient, direct comparisons could be made. To determine the price per pound of a fertilizer source two things must be known – 1) the price per ton of the fertilizer and 2) the nutrient analysis of the fertilizer. Assume urea (46-0-0) can be purchased for $500 per ton and anhydrous ammonia (82-0-0) can be purchased for $1020 per ton, which material is the cheapest?

Material price per ton
-------------------------------------------------- = Nutrient cost ($/lb of nutrient)
2000 X Material analysis (percent)

Using this equation, the urea would cost $0.54 per pound, and the anhydrous ammonia would cost $0.62 per pound. Obviously, in this instance urea is the cheaper of the two sources.

Liquid fertilizers add to the complexity of comparisons because not all fertilizer materials are marketed on a weight basis, some are sold by volume (especially starter forms of material). This can lead to confusion when attempting to determine the price per pound of a nutrient when the price is in price per volume ($/gallons typically). Each material that is sold should have a value known as specific gravity (density). This is the weight in pounds for each gallon of the material (pounds per gallon). To determine the price per pound of a nutrient for liquid materials, divide the price per gallon of material by the specific gravity multiplied by the material nutrient analysis.

Material price per gallon
---------------------------------------------------------------------------------- = Nutrient cost ($/lb of nutrient)
Specific Gravity (lb/gallon) X Nutrient analysis (percent)

Using this equation, knowing that 10-34-0 (ammonium polyphosphate) costs $6.56/gallon ($1,125/ton) and has a specific gravity of 11.67 lbs/gallon, each pound of P205 costs $1.65. Compare this to $0.98 per pound of P205 from DAP (18-46-0) at $900/ton, using the first equation. The DAP is obviously them more economical choice as a phosphorus source.

Remember, for all commercially marketed fertilizer materials the analysis of the product is guaranteed by the Ohio Department of Agriculture. And as has been stated in previous CORN articles, whatever the analysis says the material contains is what is in it. Just because someone claims their material is more “available” to the plant does not necessarily make it true (especially for the macronutrients – nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur). Some products are marketed with claims of increased availability that could save you the producer some money, and from the economic perspective you may be saving money in the short term. However, if you do the calculations you are buying a fraction of the total nutrient amount at a substantially higher cost. Even though you are paying less total, you are receiving far less total nutrient at a higher cost of pound of nutrient input. This is why these calculations are important. It is a good idea to run through these calculations when approached by someone making you an offer you cannot refuse. Some simple math can reveal that in the end you are not getting that good of a deal for what you are buying.

Now is the Time to Control Winter Annual Weed Hosts of Soybean Cyst Nematode

Authors: Kent Harrison, Anne Dorrance

Winter annuals are a specialized group of weeds that emerge from September through November in Ohio. Winter annuals go dormant during the coldest periods of winter (soil temperatures below 40 degrees), then resume rapid growth and produce seeds in the spring as temperatures increase. Some of the most common winter annuals in Ohio serve as alternate hosts of soybean cyst nematode (SCN) and can result in increased SCN egg numbers in soil if the weeds are not eliminated soon after they germinate in the fall. The most prevalent winter annual weed of Ohio and Indiana no-tillage crop fields is purple deadnettle, which unfortunately is also one of the strongest known hosts of SCN.

OSU research conducted over a five-year period indicated that SCN egg populations in soil increased three- to five fold in no-tillage soybean plots containing purple deadnettle compared to weed-free soybean plots. Purple deadnettle that emerged in October produced the highest levels of SCN reproduction. Other recent studies conducted in Ohio and Indiana have shown conclusively that SCN can infect purple deadnettle roots in the fall and can produce at least one new generation of eggs before soil temperatures drop below the 50 degree threshold for SCN development. In fields where SCN is present, it is essential that purple deadnettle be controlled within four weeks after it emerges, since SCN females can infect the weed’s roots and produce a new batch of eggs within four to five weeks. If purple deadnettle and other winter annual weed hosts are killed before SCN completes its lifecycle, the female nematodes are also killed and the SCN egg population in soil will not increase before the spring planting season.

Seedlings of purple deadnettle and other weeds that host SCN can be viewed at To control most winter annual weeds, apply Roundup Ultra at 1.0 pint per acre or Touchdown at 0.75 pint per acre plus 2,4-D ester at 1.0 pint per acre. Add Ammonium Sulfate (AMS) at 17 pounds per 100 gallon of water and Surfactant at 0.25 percent if using Touchdown. Apply when daytime temperatures are above 50 degrees and night temperatures are expected to remain above 40 degrees during the week of application.

2008 Summary and Status of Western Bean Cutworm Trapping in Ohio

Authors: Andy Michel, Ron Hammond, Bruce Eisley

During the months of July and August, we alerted growers to the increased presence of the Western Bean Cutworm (WBC) in Ohio. As harvest is ongoing, we thought it appropriate to remind growers of the status of this pest, especially if damaged ears are found that might be consistent with WBC injury. Since 2006, state specialists and extension educators have trapped for this pest. In 2006, we caught 3 adult moths, and in 2007 we caught 5. With funding from the North Central Integrated Pest Management Center, we expanded our trapping network in 2008 to include 27 counties and 57 traps. A total of 150 moths were caught in 2008, with peak flight occurring between the 18th and 25th of July. Moths were caught west of a direct line from Wayne Co. to Montgomery Co. However, over half of our total was caught in northwest OH.

Even with the large increase in trap counts, we have had no reports of egg masses, larvae, or, more importantly, damage from WBC in Ohio. Whether or not the large increase in adults caught this year will lead to population establishment and damage to corn next year in Ohio remains to be seen, but sporadic damage has been reported in IL, IN and MI. Our best management option against WBC, at least for the next few years, will continue to be trapping and scouting. If during harvest you notice heavily damaged ears, please notify entomology state specialists or your county extension educator. Ears may have feeding damage anywhere on the ear, whereas corn earworm tends to restrict feeding at the ear tip. WBC may also enter the husk by burrowing holes through the side of the ear, which provide opportunities for pathogen infection.

2008 Summary and Status of First-Year Western Corn Rootworm

Authors: Andy Michel, Ron Hammond, Bruce Eisley, Curtis Young

For the 11th year, state specialists and OSU extension educators continued to sample for adults of the first-year western corn rootworm (FYWCR). Remember, this is a variant of western corn rootworm that will lay eggs in fields other than corn - particularly soybean. Fields with FYWCR that are rotated to corn the following year will be at risk from rootworm damage. Although we are still analyzing data, we thought it best to provide some preliminary results as growers begin preparations for next year. Up to this point, we have data from 70 fields and only 5 fields were over or came close to the threshold of 5 beetles/day/trap. This number is down considerably from last year when 26 out of 93 fields reached threshold. Even though we focused our trapping this year on more central and eastern counties, we did include fields that had been historically part of this long term study and had repeatedly exceeded threshold. Very few of these fields had more than 3 beetles/day/trap. Conversations with other extension entomologists from the Midwest suggest that low numbers occurred across the corn belt. There could be many reasons for this decrease, including the cold and wet spring weather, poor adult emergence, or the presence of late-maturing corn during peak adult emergence which tends to keep adults within corn.

As mentioned, our trapping network focused more on central and eastern Ohio counties - including counties that were trapped for the first time. Most of these fields were well under threshold, but we were able to fill in some gaps in our FYWCR distribution map, namely west of Crawford County. The distribution does remain spotty, and the counties with fields over threshold had other fields that failed to reach 1 beetle/trap/day all season. It is difficult to make predictions for next year, given the non-uniform distribution and the uncharted territory of low numbers of fields over threshold that had repeatedly gone over threshold. If your fields were trapped this year, then that trapping data is still the best information in order to make management decisions. If not, then there are a few factors to consider including proximity to surveyed fields, proximity to current year's corn fields, amount of lodged corn, and past history of FYWCR as well as WCR activity. If near one of the areas where FYWCR was trapped in high numbers, then you may want to consider protecting first year corn - you can contact your extension educator for the situation in your area. Needless to say, 2009 will be an interesting year for FYWCR.

Weather Update

Authors: Jim Noel

After a decent rain over much of the state this past Friday, we now will revert back to a drier than normal pattern. However, plenty of lake effect rain and snow showers will start the week especially in the northeast section of the state. It will become dry and warmer for the second half of the week. Another weak cold front will move through Friday with spotty light showers. The next best chance for significant precipitation after early this week in the northeast section will be the middle of next week.

Overall, the pattern supports slightly colder than average temperatures and slightly drier than average precipitation through November. The exception is in the northeast lake effect area where precipitation will be near normal due to increased lake effect precipitation through November in enhanced northwest flow.

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel, and Bruce Eisley (Entomology), Peter Thomison (Corn Specialist), Mark Loux (Weed Science), Robert Mullen and Keith Diedrick (Soil Fertility), and James Noel (NOAA/NWS/OHRFC). Extension Educators: Roger Bender (Shelby), Glen Arnold (Putman), Harold Watters (Champaign), Todd Mangen (Mercer), Mike Gastier (Huron), Les Ober (Geauga), Tim Fine (Miami), Bruce Clevenger (Defiance), Wesley Haun (Logan), Steve Foster (Darke), and Curtis E. Young (Allen).

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.