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Ohio State University Extension

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C.O.R.N. Newsletter: 2014-29

  1. Assessing the risk of frost injury to late maturing corn

    Author(s): Peter Thomison

    According to the National Agricultural Statistics Service (http://www.nass.usda.gov/) as of August 31, 87 percent of Ohio’s corn acreage was in the dough stage (R4), nearly the same as the five-year average of 88 percent. Forty-one percent of the corn acreage was in the dent stage (R5), compared to 49 percent for the five-year average. In some areas of the state corn is considerably behind the five-year average because of late planting ( the result of persistent rains and excessively wet soils that delayed planting in some localized areas) and cooler than normal temperatures in July. This later than normal maturation of the corn crop had led to questions about the likelihood for frost damage and whether more fuel will be needed to dry corn.

    In Ohio, physiological maturity (when kernels have obtained maximum dry weight and black layer has formed) typically occurs about 65 days after silking. At physiological maturity (kernel moisture approximately 30-35%), frosts have little or no effect on the yield potential of the corn crop.

    Dr. Bob Nielsen at Purdue University has summarized research findings from Indiana and Ohio that provide insight into both the calendar  days and thermal time (growing degree days, GDDs)  typically required for grain at various stages of development to achieve physiological maturity (kernel black layer, R6). This research was conducted at two locations in Indiana (west central and southeast) and two locations in Ohio (northwest and southwest) with three hybrids representing 97, 105, and 111 "day" relative maturities planted in early May, late May, and early June. The calendar days and thermal time from silking to black layer for the 111-day hybrid maturity are shown in Table 1 (fromhttp://www.agry.purdue.edu/ext/corn/news/timeless/RStagePrediction.html).

    The study indicated that corn planted in early June compared to early May requires 200 to 300 fewer GDDs to achieve physiological maturity.  According to Dr.Nielsen, while slightly different responses among the four locations of the trial existed, there did not seem to be a consistent north / south relationship. Therefore, growers can use the results summarized in the following table to "guesstimate" the number of calendar days or heat units necessary for a late-planted field at a given grain fill stage to mature safely prior to that killing fall freeze.

    How many GDDs can be expected from now until an average date of a killing frost for an adapted 111 day hybrid planted in mid June?  To answer this question, estimate the expected GDD accumulation from Sept. 2 until the average frost date (50% probability) for different regions of the state (Table 2).  These GDD expectations are based on 30-year historical normals reported by the Ohio Agricultural Statistics Service. The GDD accumulation was calculated using the 86/50 cutoff, base 50 method.

     If you want to determine the "youngest stage of corn development" that can safely reach black layer before the average frost date at a given weather station, use the information in Table 2 on remaining GDD in conjunction with Table 1 which indicates GDDs needed to reach black layer at various stages of grain fill. Compare "GDDs remaining" for the site with the GDD required to achieve black layer depending on the corn's developmental stage. 

    Table 2. Estimated GDDs remaining from Sept. 2 to the first fall frost for Ohio.

     

    Region

    Median Frost Date

    (50% probability)

    Estimated GDDs Remaining

    From Sept. 2 to Fall Frost

     

     

     

    Northwest

    Oct 10 – Oct 20

    412 - 462

    North Central

    Oct 10 – Oct 25

    400 - 485

    Northeast

    Sept 30 – Oct 25

    351 - 497

    West Central

    Oct 10 – Oct 15

    447 - 504

    Central

    Oct 5 – Oct 15

    461 -522

    East Central

    Sept 30 – Oct 15

    377- 495

    Southwest

    Oct 10 – Oct 15

    473 - 536

    South Central

    Oct 15 – Oct 20

    554 - 606

    Southeast

    Oct 5 – Oct 15

    447 - 507

    If your corn is in the dent stage (R5) as of Sept. 2, will it be safe from frost? Table 1 indicates that corn planted in mid - June required about 217 GDDs to reach black layer from R5 and Table 2 indicates that all regions of the state are likely to accumulate sufficient GDDs before the 50% frost date.

    However, if your corn is in the “milk” stage (R3) as of Sept. 2, it might be a different story. The kernel development - GDD accumulation relationships in Table 1 indicate that corn planted in mid-June that is at R3 needs about 681 GDDs to reach black layer. Table 2 indicates that only one region of the state (south central Ohio) comes close to accumulating that number of GDDs before the 50% frost date with the East Central and Northeast regions least likely to accumulate the GDDs required to achieve physiological maturity.

    The research results in Table 1demonstrate that late planted corn has the ability to adjust its maturity requirements, and most of this adjustment occurs during the late kernel development stages. In previous growing seasons when GDD accumulation was markedly less than normal, the corn crop has usually achieved physiological maturity before the first frost occurred.

     References

     Nielsen, R.L. 2011. Predicting Corn Grain Maturity Dates for Delayed Plantings

    Corny News Network, Purdue Univ. [On-Line]. Available athttp://www.agry.purdue.edu/ext/corn/news/timeless/RStagePrediction.html

  2. FSR CCA College: Register by September 4th

    The weather forecast is for 75 degrees and partly cloudy; a perfect day to be outside. This late summer update for agronomist and those advising growers on crop production will be held on September 9th from 8:45 until 3 pm at the Farm Science Review Site at 135 SR 38NE, London OH. The program is intended for all experience levels and non-CCA’s as well. We’ll meet in the Agronomic Crops Team Demonstration plots at the east end of the FSR grounds; enter off US 40 for parking – convenient:http://fsr.osu.edu/resources/documents/pdf/maps/exhibit-map-august-2014.

     Topics include:

    • What are your neighbors thinking about GMOs? Jennifer Coleman, Ohio Soybean Council.
    • Stink bugs, stink bugs - managing late season insects. Andy Michel, should you be spraying your soybeans at R5?
    • What does the new "Phosphorus" law mean to your business? Greg LaBarge, will also discuss placement and timing of fertilizers.

    • Have you seen this weed? No actually this time it's Giant ragweed. Mark Loux, will discuss current problems and expectations for the future.
    • Do soybeans respond to added nitrogen? Laura Lindsey, will also discuss other management practices for soybean improvement
    • You want a drone? But what will you do with it? - John Barker CCA, drone owner.
    • You have got to be kidding me with these fungicide applications! Anne Dorrance on yield impacts of soybean diseases.
    • More leaf diseases than I have ever seen. Pierce Paul, schemes for control of corn leaf disease.
    • How much N do you need for corn? Steve Culman, attacking the other side of the nutrient management problem.
    • It has not been a perfect year - so how do we manage stress in corn? Peter Thomison, maybe it's about water.

    Visit https://agcrops.osu.edu/calendar. For complete details and to register usehttp://go.osu.edu/FSRCCA using a credit card or check. If you have further questions contact Harold Watters at watters.35@osu.edu or (937) 604-2415.

    Preregistration requested by end of day September 4th; cost is $75.

  3. We’re looking for a few good Amaranth populations

    Author(s): Mark Loux

    OSU weed science is once again looking for seed from populations of Amaranth species – waterhemp, Palmer amaranth, and redroot/smooth pigweed – to screen for herbicide resistance this winter.  We will be collecting seed from infested fields we encounter during our annual survey of the state next month.  We would also encourage readers to submit seed from problem Amaranth populations in their fields.  Amaranth seed are mature when small black seeds fall out of the seedhead when it is shaken or rapped against something.  Seedheads should be cut off and stored in open paper bags to allow further drying, until arrangements can be made to get them to us.  Seed samples should be accompanied by a sample submission form, which is available on our website –http://u.osu.edu/osuweeds/.  The goals of this effort are to:

    1) characterize current infestations of herbicide-resistant waterhemp and Palmer amaranth to be able to provide guidance on herbicide programs in infested fields.

    2) determine whether resistance is starting to occur in redroot and smooth pigweed.

    3) provide information to our clientele about the distribution of resistant populations, and the trends in herbicide resistance development.

    For more information contact Mark Loux, loux.1@osu.edu, 614-292-9081.

  4. Farm Science Review 2014: Plan your show

    Plan to attend the 2014 Farm Science Review September 16th-18th in London, Ohio. The FSR show hours are: Tuesday and Wednesday 8:00 am to 5:00 pm; Thursday 8:00 am to 4:00 pm.  You can plan your show now by visiting fsr.osu.edu and looking at the Schedule of events, Exhibit area maps, and 2014 Exhibitor listings. Field demonstrations will occur daily depending on weather starting at 12:30 pm. Some of those demonstrations include corn and soybean harvesting, tillage, nutrient application including gypsum, planter technology, UAV (drones), and field drainage installations including controlled drainage.  Be sure to visit the AgCrops Team demonstration plots as you enter the show from the public parking lot. Other areas to visit are the Utzinger Memorial Garden, Center for Small Farms, Question the Authorities, and The Gwynne Conservation Area. Be sure to download the 2014 Farm Science Review mobile app from fsr.osu.edu or the app stores before attending the show. The app will be released soon and available for download prior the show. Visitor golf car information is also available for attendees with special needs on thefsr.osu.edu website. See you at the show!

  5. Will the late increase in soybean aphid hurt yield?

    Author(s): Andy Michel

    Over the last two weeks, many growers have seen rapid increases in soybean aphid populations.  This is similar to the late outbreak seen last year, when aphids infested during the R5-R6 growth stage transition.  As a reminder, it takes a lot of soybean aphid to impact yield after the R6 growth stage, likely above 1,000 aphids per plant.  Even at R5 and below, aphids do not hurt yield until ~500-600 aphids per plant.  Then why the 250 aphids/plant threshold?  The 250 threshold allows for the time it takes for an application, such that by the time a spray could occur, aphids are close to the 500-600 aphids per plant level.  Given the late planting season some growers had, here are some suggestions to follow if your soybeans are at the R5-R6 transition and you have 250 aphids per plant:

    1) Check again in 3-4 days, are the aphids increasing (remember the threshold is a RISING population of 250 per plant)? At many sites, natural enemies like lady beetles are keeping aphids down.

    2) At this point in the summer, you can expect aphids to double in size in about a week. Do you think you will reach R6 before aphids get to 500 per plant? If so, then it probably won’t pay to treat. Bottom line is predicting the aphid population size when you get to R6—as long as that is lower than ~1,000 aphids per plant, you should be fine.

    3) Do you have to use ground equipment?  Then expect a 2-3 bushel loss on yield which might impact whether or not you see a return on the application cost.

  6. Ohio no-till field day announced

    Author(s): Randall Reeder

    The Ohio No-Till Field Day will be Sept. 9 at John Buck’s farm in western Marion County (7632 Wildcat Pike, New Bloomington). The emphasis of the program is to provide a systems approach to make continuous no-till successful, not just individual components.

    The morning speakers are Barry Fisher, State Agronomist for NRCS in Indiana, Hans Kok, coordinator of the Conservation Cropping Systems Initiative in Indiana, and Ed Winkle, Hymark Consulting, in southwest Ohio.After lunch topics in the field include precision manure application, cover crop plots, high clearance cover crop seeding, and two soil pits.

    Speakers include Brad Mattix, Clark Hudson, Ann Brandt, David Brandt, and George Derringer.The program begins at 9:00 a.m. and will end about 4:00 p.m. Lunch is included. Registration and a detailed agenda are online at: fabe.osu.edu/notill.

  7. Last alfalfa cutting of the year

    Author(s): , Mark Sulc

    The cool, wet spring followed by rainy weather well into the summer has delayed hay cutting schedules across much of Ohio. The delayed cutting schedules will likely mean that many fields won’t be ready for a last harvest until we are into the critical fall rest period for alfalfa, considered to be from September 7 to 15 to late October in Ohio. Careful consideration is warranted if this is the situation. 

    Cutting during the critical fall rest period if often practiced in Ohio without great harm to the stand, but it always carries risk to stand health. The fall period is when alfalfa and other tall legumes like red clover undergo many physiological responses to the cooling weather in preparation for the winter. Carbohydrate and protein reserves are stored in the crowns and roots and cold-hardening occurs that makes the plants more resistant to cold temperatures. Interrupting this process by cutting carries the risk of the plants having inadequate energy and protein reserves to make it through the winter and for initiating vigorous regrowth next spring. It also may interrupt the cold acclimation process.

     A number of factors affect the level of risk incurred cutting during the critical fall period. These include overall stand health, variety disease resistance, insect pests during the summer, age of stand, cutting management, fertility, and soil drainage. 

     A vigorous, healthy stand is more tolerant of fall cutting than a stressed and weakened stand. Protection from potato leafhopper stress during the year is important for maintaining strong and vigorous plants that are able to withstand a fall cutting stress. Alfalfa varieties with improved disease resistance and good levels of winter hardiness will be more tolerant to negative effects of a fall cutting because there is less total stress on the plant. Adequate fertility, especially soil potassium levels, increase plant health and plant tolerance to fall cutting effects. A high soil pH of 6.8 to 7.0 will also reduce the risk of fall cutting. Stands under 3 years of age are more tolerant of fall cuttings as compared to older stands where root and crown diseases are setting in. 

     A significant risk factor to consider when making a harvest during the critical fall period is the number of times the stand has been harvested.  Alfalfa that has been cut three or more times before a fall harvest has a higher risk factor for injury due to fall harvest than one cut only twice. In other words, the cutting frequency during the growing season can affect the energy status of the plant going into the fall. Frequent cutting (30 day intervals or less) results in the plant never reaching full energy reserve status during the growing season. This makes the critical fall rest period more necessary for plants to accumulate adequate reserves before winter.

     A final factor is soil drainage. Alfalfa stands on well-drained soils tolerate later fall cuttings better than alfalfa on moderately or poorly drained soils.  Low plant cover going into the winter from late cutting increases the risk of winter heaving on many Ohio soils. We observed significant heaving this past winter in NE Ohio, and many of those stands had been harvested during the previous fall.

     Cutting alfalfa during the critical fall period is sometimes necessary due to the need for forage or weather patterns like we’ve experienced this year. It often does not cause great harm to the stand, but there is always risk of reduced vigor with some yield loss next year, or even significant stand loss depending on the winter. So carefully assess the condition of your stand and the risk factors discussed in this article. If you do cut during the fall critical rest period, leave some uncut strips in different areas of the field so you can compare the regrowth next spring. You might be surprised by what you learn.

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.

Contributors

Anne Dorrance (State Specialist, Soybean Diseases)
Eric Richer, CCA (Field Specialist, Farm Management)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Sam Custer (Educator, Agriculture and Natural Resources)
Sarah Noggle (Educator, Agriculture and Natural Resources)

Disclaimer

The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.