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April 21-28, 2003
C.O.R.N. 2003-10
In This Issue:
A) Corn Emergence and Early Plantings
B) Managing "Pollen Drift" in Ohio Corn Fields: Planting
Considerations
C) Pop-Up Fertilizers
D) The Latest on Weed Emergence & Marestail Identification
in the Field
E) Wheat is Jointing - Fewer Herbicide Options!
F) Accurate Soybean Seeding Rates Save Money
G) Soybean Inoculation Update
H) Bean Leaf Beetle Update
There have been reports that as much as 20 to 30% of the corn acreage has been planted in some western Ohio counties. Favorable weather and soil conditions have allowed earlier than normal planting of many corn fields.
Corn requires about 100 growing degrees days (GDDs) to emerge (note that emergence requirements can vary from 90 to150 GDDs). To determine daily GDD accumulation, calculate the average daily temperature (high + low)/2 and subtract the base temperature which is 50 degrees F for corn. If the daily low temperature is above 50 degrees, and the high is 86 or less, then this calculation is performed using actual temperatures, but if the low temperature is less than 50 degrees, use 50 degrees as the low in the formula. Similarly, if the high is above 86 degrees, use 86 degrees in the formula.
If it takes a corn hybrid 100 GDDs to emerge, and daily high and low temperatures average 70 and 50 degrees following planting, 10 GDDs accumulate per day, and corn should emerge in about 10 days (100 GDDs to emerge/10 GDDs per day = 10 days). However, if daily high and low temperatures are cooler, averaging 60 and 45 degrees after planting, 5 GDDs accumulate per day, and it may take nearly 3 weeks (100 GDDs to emerge/5 GDDs per day = 20 days) for corn to emerge.
Given this relationship between GDD accumulation and emergence, growers should
not be too surprised if their early to mid April planted corn will require more
time to emerge than later planted corn. While air temperatures have generally
been warmer than average recently with high temperatures near or slightly above
80 degrees, soil temperatures (as measured at the 2-inch soil depth) have been
considerably cooler, in the 50 to 60 degree F range. Seedling emergence is dependent
on soil temperature and air temperature. The immediate forecast is for a return
to cooler, more seasonable temperatures. Also, keep in mind that these estimates
of emergence based on GDDs are approximate and can be influenced by various
factors including residue cover, tillage, and soil organic matter (soil "color")
and moisture content.
Isolation and Border Rows
One of the most effective methods for preventing pollen contamination is use of a separation or isolation distance to limit exposure of non-GMO corn fields from pollen of GMO fields. The potential for cross-pollination decreases as the distance between GMO and non GMO corn fields increases. Several state seed certification agencies that offer IP grain programs require that non-GMO IP corn be planted at a distance of at least 660 ft from any GMO corn. This isolation distance requirement may be modified by removing varying numbers of non-GMO border rows, the number of which is to be determined by the acreage of the non-GMO IP corn field. The border rows ensure that the non-GMO field is "flooded' with non-GMO pollen which will dilute adventitious pollen from a GMO source. For IP corn fields over 20 acres in size, the isolation distance (of 660 ft) may be modified by post pollination removal of 16 adjacent border rows if the actual isolation distance is less than 165 feet; the distance may be modified by post pollination removal of 8 adjacent border rows if isolation distance is between 165 and 660 feet. These isolation and border row requirements are designed to produce corn grain that is not more than 0.5% contaminated with GMOs.
Planting Dates and Hybrid Maturity
Use of different planting dates and hybrid maturities can also be used to reduce the risk of cross-pollination between fields of GMO and non-GMO corn. For example, planting a short season non-GMO corn hybrid followed by full season hybrid later will reduce the chance for pollen from the GMO field to fertilize the early planted, earlier maturity non-GMO hybrid in an adjacent field. However, there are shortcomings with this approach. Differences in maturity between the early and late hybrid may not be large enough to ensure that the flowering periods of each hybrid will not overlap, especially when unusual climatic conditions accelerate or delay flowering. Moreover this strategy will only work if you control the adjacent fields or can closely coordinate your corn planting operations with those of your neighbors.
Prevailing Wind Direction
Agronomists in states to the west of Ohio indicate that the south and west edges of non-GMO fields may be more vulnerable to pollen drift because the prevailing during the summer are from the southwest. In Ohio, I'm not sure how consistent this wind pattern is but if it is an issue, then it may be particularly useful to follow recommendations regarding isolation distances and border row on these sides of non-GMO fields.
Other Considerations
Other factors that can negatively impact non-GMO grain purity are volunteer corn plants resulting from no-till or minimum till continuous corn, purity level of the seed planted, planting errors, and drought or flood conditions which stunt border rows and reduce desirable pollen production and flow.
Planting operations to manage pollen drift are only part of the process of
producing an IP corn grain crop. Other major issues include harvesting, drying
and storage, along with thorough record keeping. Seed certification agencies
like the Ohio Seed Improvement Association (http://www.ohseed.org/) offer IP
programs for grain. These IP programs, which are similar to seed certification,
assist in preserving the genetic identity of a product, and verify specific
traits through field inspections, laboratory analysis, and record keeping.
We have received many calls on pop-up fertilizers. Pop-up or placement of the fertilizer directly with the seed has the potential to cause significant stand reduction depending on soil moisture and soil texture (damage potential increases with dry conditions and sandy soils). To lower this risk, apply no more than 5 lb/A of combined N and K on soils with a CEC < 7 and no more than 8 lb/A on soils with CEC > 8 for pop-up applications. Lower equipment costs and faster application are the main advantages for the pop-up system. Injury risk and the restriction on N rates are the main disadvantages (research has shown that most of the yield advantage from starter fertilizers comes from N).
Unfortunately, some producers have been told that the plants emerge faster and utilize fertilizer more efficiently when applied close to the seed. Some have suggested that this occurs because of the liquid, low salt formulation. Research has not shown that seedlings emerge faster from a pop-up system compared to a 2 x 2 placement system (2 inches below and to the side of the seed). For the first three weeks after emergence the plant relies on nutrients from the seed and not fertilizer. By the time the seed reserves are depleted, nodal root development should be adequate to reach the 2 x 2 band. Dry and liquid fertilizers generally behave similarly in the soil for a given macronutrient, i.e. liquids are not more available to the plant than dry material. Producers should base their decisions on their application equipment and fertilizer cost rather than liquid versus dry material.
Some producers have been encouraged to use both a pop-up and a 2 x 2 band starter for maximum growth and yield benefits. There is no research data to support this theory. It would be redundant to use both systems in the same field and would only increase fertilizer costs and application time.
In summary, a 2 x 2 band is the preferred placement of starter fertilizer because
of low risk of injury to the seed and seedlings, and consistency in performance.
Pop-ups may be used because of equipment availability and application ease,
but in some years, stand losses may occur depending on weather conditions and
N and K rates. Additional information may be found in Extension Bulletin E-2567,
"Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat & Alfalfa."
The next group of weeds beginning to emerge includes: velvetleaf, giant foxtail, hemp dogbane, and field bindweed are starting to emerge based upon observations near campus. At this time, most burn-down herbicides should take out the small foxtails, but soon glyphosate or paraquat will need to be added to all burn-down herbicides in order to control the annual grasses that have emerged.
Currently, marestail plants are still in the rosette stage. Fleabanes have
begun to bolt (produce a stem). This is the easiest way to identify these species
at this time.
Wheat in central and southern Ohio has reached the jointing stage (Feeke's Stage 6) of development. A few reminders on the use of wheat herbicides as the crop reaches jointing:
We have conducted twelve soybean seeding rate studies during the past two years and have learned two important facts about how seeding rate effects soybean profit. The most profitable seeding rate is a function of both the growing conditions in the field and also the cost of the seed.
The research data from those twelve studies indicate that in areas of a field where good plant growth occurs, the most profitable seeding rate was around 145,000 seed per acre. In areas of fields where plants did not grow well the most profitable seeding rate was about 200,000 seed per acre. In other words, the bigger the plants are, the fewer of them you need for maximum yield.
Although yield is not a function of seed cost, crop profit is a function of seed cost. In calculating the profit from various seeding rates we found that as the seed cost increases, the most profitable seeding rate decreases regardless of the growing conditions or the yield. For seed costing $20 per 50 pound unit, the most profitable seeding rate was at 15,000 fewer seeds per acre than for seed costing $12 per 50 pound unit.
We counted plant populations at maturity and found that for good growing conditions we needed only about 100,000 plants per acre at harvest for maximum yield. However, in poor growing conditions where plants did not get big, we needed 130,000 plants per acre to get the maximum yield.
Recommendations for 7.5 inch rows: 1) Reduce seeding rates to about 160,000 seeds per acre on your most productive soil. 2) If the seed is expensive ($20 per 50 pounds), reducing the seeding rate about 15,000 seeds per acre will increase profit $2.50 per acre. 3) Small seed is a better buy than big seed because you get more seed per bag and per dollar. 4) To determine the seed spacing for 7.5 inch rows, dividing the number of seeds per acre you want to drop into 836,000 to get the spacing (inches) between seeds in the row. If you drop 200,000 seed per acre, the seeds will be 4.2 inches apart. For 150,000 they will be 5.6 inches apart. 5) Calibrate drills and planters to deliver the proper number of seed per foot of row rather than a given number of pounds of seed per acre. 6) Calibrate, Calibrate, Calibrate; it=s the profitable thing to do.
A soybean crop will use almost 5 five pounds of Nitrogen to produce a bushel of soybeans and each bushel of grain contains up to 4 pounds, depending on the grain protein content. Some of this nitrogen will come from the breakdown of soil Organic Matter, but most comes from the production of nitrate by a nitrogen fixing bacteria called Bradyrhizobium. The Bradyrhizobium bacteria in soybean inoculation products is mush more productive than the Rhizobia strains already in the soil. The benefit of using the new and improved strains is increased yield due to increased fixation of Nitrogen by these superior strains. In 55 field trials since 1995 we have recorded yield increases ranging from a few pounds per acre to just over 10 bushel per acre. All this testing was conducted on fields where we would not expect a yield increase form inoculation because the soil pH and nutrient levels were good and the crop rotation was corn-soybean. However, the average yield increase from those 55 field trials is just under two bushels per acre. When inoculation costs only two to three dollars per acre there is a good profit from inoculating. The Rhizobia are living bacteria cells and they sometimes do not survive to infect soybean roots if the soil is very wet, very hot of very dry after planting, so a yield increase is not guaranteed, but over time, it pays to inoculate.
Inoculation material is available in both dry and liquid form and both can be applied by hand or mechanically. Some products are formulated to allow application to seed up to 30 days before planting if the seed does not already have a fungicide applied. These same products can be applied up to 7 days pre plant when some fungicides are already on the seed. Most products should be applied to the seed when the seed is loaded into the planter or drill and planting should be accomplished no more than 12 hours after treatment. Most products are formulated for application to seed, but some can be furrow applied if a planter or drill is equipped to meter the material. Furrow application is much more expensive than seed application but would have advantage in wide rows where soybeans have not been grown previously.
Inoculation materials may be safely applied to seed already treated with fungicides such as: ApronMaxx RTA, Warden RTA, Apron XL, and Allegiance. Other fungicides may be compatible with inoculation materials and are currently being evaluated. When in doubt about compatibility, ask your seed supplier about the fungicide on the seed and its compatibility with inoculation materials.
Growers should plan on monitoring their soybean fields for the presence of abnormally high populations of bean leaf beetle. Although populations were not especially high during most of 2002, we saw many fields in the fall with significant numbers. If early defoliation reaches 50%, plants appear stunted, and stand loss appears imminent and insects are still active, insecticide treatment would be recommended. Remember that bean leaf beetles tend to be most numerous in early-planted fields. Thus, growers who plant their soybean fields early, especially relative to other fields in their areas, should watch their fields more closely. Additionally, there is still the concern among growers with the beetle's ability to vector bean pod mottle virus. The bean leaf beetle transmits this virus, especially in early season during feeding by the over-wintering beetle. At present, we do not recommend treating the soybeans for bean leaf beetle to protect the plant from the virus. However, some growers may choose to take this approach. Initial studies out of Iowa State University suggest that the best control of the virus will be achieved by spraying for the bean leaf beetle at the VE-VC stage after the soybeans emerge from the soil and when beetles are first seen in the field. Their data also suggest that for optimal control of the virus, a second spray against the beetle is necessary in July at the occurrence of the first beetle generation.
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Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/
C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.
State Specialists: Pat Lipps, Anne Dorrance & Dennis Mills (Plant Pathology), Mark Loux and Jeff Stachler (Weed Science), Jim Beuerlein ( Soybean Production), Bruce Eisley (IPM) , Peter Thomison (Corn Production , and Ron Hammond (Entomology); District Specialists: Ed Lentz (Agronomy); Extension Agents: Bruce Clevenger (Defiance), Roger Bender (Shelby), (Clark Hudson (Seneca), Barry Ward (Champaign), Howard Siegrist (Licking), Jim Lopshire (Paulding), Mark Koenig (Sandusky), Greg La Barge (Fulton), Gary Wilson (Hancock), Harold Watters (Miami) and Steve Prochaska (Crawford).Editor: Steve Prochaska Web Editor: Nathan Watermeier
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