Growing Degree Days vs. Calendar Days – How Long Will Emergence Take?

Source: Alexander Lindsey, Greg LaBarge, OSU Extension

When we examine crop emergence post-planting, two factors can impact speed of emergence – soil moisture content and soil temperatures. If soil temperatures are lower, it can take more calendar days for emergence to occur meaning rowing corn may take a little more time. In the Ohio Agronomy Guide, emergence should begin to occur after approximately 100 air GDDs.

A difference in 10 degrees in temperature can dramatically affect how quickly crops will emerge. For example, at a temperature of 60 degrees F heat unit accumulation per day would be 60 F – 50 (base temperature for growth) = 10 GDDs. If it takes 100 GDDs to start to see emergence, at this rate it would take 10 calendar days to see the crop start to emerge. If temperatures are 70 degrees F, heat unit accumulation per day would be 70 F – 50 = 20 GDDs. This would shorten the emergence window to 5 calendar days instead, resulting in more rapid emergence from planting.

Figure 1. Emerged corn on May 6, 2021 planted April 19 near London, OH.

In recent work from Nemergut et al. (2021), researchers from OSU observed emergence starting at 110 to 120 soil accumulated GDDs (base of 50 degrees F) for corn, which equated to first emergence observed in 4 or 5 days after planting. Some of the difference in calendar date for emergence (though GDD accumulation was similar) was because planting depth was changed, and the 1” planting accumulated GDDs faster than the 2” and 3” planting depths. These studies though were planted in May or early June (2019 wet spring delayed planting), and daily accumulated GDDs was higher than we might expect if planted in late April. Soil accumulated GDDs have been discussed above, and these could vary slightly compared to air accumulated GDDs (calculated using air temperatures). In the work referenced above, accumulated air GDDs in the first four days post-planting were 106-118 GDDs, slightly less than the soil accumulated GDDs.

If you want to predicate emergence on your farm, the GDD calculator found at https://mrcc.illinois.edu/U2U/gdd/ is a useful tool. It is a two-step process, first find your location on the map, then enter your planting date. The graph will display accumulated GDD’s for your location. Example output in Figure 2 shows GDD accumulation from an April 19, 2021 planting date near London, OH in Madison County. By May 6 the accumulated GDD was 138 and the emerging corn is shown in Figure 1. The GDD calculator can be used to predict growth stage throughout the growing season. This is a handy to time when scouting and management decisions should be made.

Figure 2. GDD accumulation from April 19 to May 6, 2021 near London, OH.

As the days turn cooler, don’t be surprised if the crops don’t pop out of the ground quickly due to lower soil temperatures. If emergence is still not observed after two weeks, it may be worth checking the field to see if other issues may be affecting emergence.

Soil Moisture & Corn Seed Depth

Source: Dr. Bob Nielsen, Purdue Univ.

Bottom Line: Uniformly adequate soil moisture at seeding depth is important for assuring rapid and uniform germination of a newly planted corn crop. Take time to assess soil moisture at your selected seed depth on the day of planting. If soil moisture is not available or unevenly available at your normal seeding depth, then consider planting deeper than normal if soil moisture is available at those deeper settings.

Uniformly adequate soil moisture at seeding depth is important for assuring rapid and uniform germination of a newly planted corn crop. Take time to assess soil moisture at your selected seed depth on the day of planting. If soil moisture is not available or unevenly available at your normal seeding depth, then consider planting deeper than normal if soil moisture is available at those deeper settings.

Choice of seeding depth for corn is often paid scant attention by growers during the rush of planting their crop. Human nature being what it is, we tend to simply leave the planter’s depth control setting at the same position as it was in previous years. While it is true that a seeding depth of 1.5 to 2 inches is a fairly all-purpose range that works well in most situations, certain conditions merit more attention to seeding depth, the most common factor being soil moisture.

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Corn, Soybean and Wheat Enterprise Budgets – Projected Returns for 2021 Increasing Fertilizer Prices May Force Tough Decisions

Source: Barry Ward, John Barker, OSU Extension

The profit margin outlook for corn, soybeans and wheat is relatively positive as planting season approaches. Prices of all three of our main commodity crops have moved higher since last summer and forward prices for this fall are currently at levels high enough to project positive returns for 2021 crop production. Recent increases in fertilizer prices have negatively affected projected returns. Higher crop insurance costs as well as moderately higher energy costs relative to last year will also add to overall costs for 2021.

Production costs for Ohio field crops are forecast to be modestly higher compared to last year with higher fertilizer, fuel and crop insurance expenses. Variable costs for corn in Ohio for 2021 are projected to range from $386 to $470 per acre depending on land productivity. Variable costs for 2021 Ohio soybeans are projected to range from $216 to $242 per acre. Wheat variable expenses for 2021 are projected to range from $166 to $198 per acre.

Returns (excluding government payments) will likely be higher for many producers depending on price movement throughout the rest of the growing year. Grain prices currently used as assumptions in the 2021 crop enterprise budgets are $4.30/bushel for corn, $11.55/bushel for soybeans and $6.25/bushel for wheat. Projected returns above variable costs (contribution margin) range from $216 to $434 per acre for corn and $284 to $509 per acre for soybeans. Projected returns above variable costs for wheat range from $193 to $342 per acre. As a reminder, fixed costs (overhead) must be paid from these returns above variable costs. Fixed costs include machinery ownership costs, land costs including rent and payment for owner operator labor and management including other unpaid family labor.

Fertilizer prices continue to increase.  If you have not checked fertilizer prices lately, be prepared for some sticker shock. Producers with some fertilizer purchased and stored or pre-priced prior to recent price increases will likely see a healthier bottom line this upcoming crop year.

Those with little or no fertilizer pre-purchased and stored or pre-priced may want to consider using P and K buildup to furnish crop needs this year in anticipation of possibly lower prices in the future.  Now may be a good time review your fertilizer plans as you are considering how to best utilize your financial resources in 2021.

  • Use realistic yield goals.  Yield goals vary by field.  Each field has unique characteristics that can impact yield.
  • Utilize crop removal rates to determine crop nutrient needs.  Crop removal rates can be found in the new Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa (Tables 15 and 16), available at your local Extension Office.
  • Start with a recent soil test.  If your soil test levels are in the maintenance range or higher, 2021 may be a good year to “borrow” from your soil nutrient bank.

As an example, a 150-bushel corn crop will remove about 55 pounds of P2O5 per acre in the harvested grain.  This would result in a reduction in the soil test level of approximately 3 ppm.

Current budget analyses indicates favorable returns for soybeans compared to corn but crop price change and harvest yields may change this outcome. These projections are based on OSU Extension Ohio Crop Enterprise Budgets. Newly updated Enterprise Budgets for 2021 have been completed and posted to the Farm Office website: https://farmoffice.osu.edu/farm-mgt-tools/farm-budgets

 

Corn and Soybean School: Q and A on Corn Disease Management with Fungicides

On Feb 11, 2021, I gave a talk entitled “Management of Gibberella ear rot and Vomitoxin in Corn with Fungicides: Lessons Learned from Head Scab” as part of the 2021 Virtual Corn and Soybean School. I summarized years of fungicide efficacy research on head scab, a disease of wheat caused by the same fungus (Fusarium graminearum [Gibberella zeae]) that causes Gibberella ear rot (GER) in corn. Head scab and vomitoxin in wheat have been more widely studied than GER and vomitoxin in corn, as a result, a lot more is known about fungicide efficacy against scab/vomitoxin than against GER/vomitoxin. I therefore used lessons learned from head scab research, coupled with data from a limited number of GER fungicide efficacy studies to provide guideline on GER and vomitoxin management in corn. More than 220 people attended the 40-min-long program, asking questions covering various aspects of corn pathology. Below are more complete responses to several of these questions:

Q: How do you explain high vomitoxin levels in grain with no apparent ear rot observed?  Can drought stress alone be a culprit?

A: Infection of the ear, development of visual symptoms (ear rot), and contamination of grain with vomitoxin all depend on weather conditions during the weeks after silk emergence. Once the fungus enters the ear via the silks (infection) and begins to colonize the developing grain, it produces vomitoxin, even if subsequent weather conditions are not favorable for mold and ear rot to develop on the outside of the ear. This is particularly true if infections occur late and conditions become relatively dry and unfavorable for visual symptoms to develop.

Q: It looks like the triazoles are doing the work on VOM, more than strobies, is this correct?

A: Pulling from my years of experience with head scab and a limited number of fungicide efficacy studies on Gibberella ear rot and vomitoxin in corn, I would be more inclined to recommend a triazole than a strobilurin fungicide for Gibberella ear rot and vomitoxin control in corn. Miravis Neo (a combination fungicide of a triazole, an SDHI, and a strobilurin) also looks promising.

Q: Is there any relationship between using a strobilurin for vomitoxins in corn compared to what is found in wheat?

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Corn College and Soybean School

The Agronomic Crops Team will host a virtual Corn College and Soybean School on February 11, 2021. Corn College is in the morning, from 9:00 – 12:00pm, with Soybean School in the afternoon from 1:00-4:00pm. Each program will feature updates from OSU Specialists. CCA CEUs are available. The schedule for the day is as follows:

 

Corn College, 9:00am-12:00pm

  • Corn Management for 2021, Peter Thomison, 1.0 CM CCA CEUs
  • Meeting Nutrient Needs in Corn, Steve Culman, 1.0 NM CCA CEUs
  • Disease Management, Pierce Paul, 1.0 PM CCA CEUs
  • Insect Management, Andy Michel, 1.0 PM CCA CEUs

Soybean School, 1:00-4:00pm

  • Soybean Management for 2021, Laura Lindsey, 1.0 CM CCA CEUs
  • Weed Management, Mark Loux, 1.0 PM CCA CEUs
  • Disease Management, Anne Dorrance, 1.0 PM CCA CEUs
  • Insect Management, Kelley Tilmon, 1.0 PM CCA CEUs

This program is free to attend. Register at www.go.osu.edu/agronomyschools.

Ag Tech Tuesdays

The Ohio State Digital Ag Team’s Ag Tech Tuesday webinars are continuing this month! The online February series will cover results from several 2020 eFields trials and be held each Tuesday starting at 10:00 EST for 1 hour. There will be plenty of time for participants to ask questions.  The following provides details for the 2021 Ag Tech Tuesday sessions.

 

2021 AG TECH TUESDAY: EFIELDS RESULTS

  • February 2 – Improving Profitability in Corn Production

Weather and Climate Trends, Aaron Wilson

Irrigation, Amanda Douridas and Will Hamman

Corn Seeding Rates, Chris Zoller

SmartFirmer Seeding Rate, Elizabeth Hawkins

  • February 9 – Pushing Soybean Productivity in Ohio

Boots on the Ground, Laura Lindsey

Local Boots on the Ground Results, Mary Griffith

Foliar Fertilizer, James Morris

Soybean Seeding Rates, Ken Ford

Sulfur on Soybeans, John Barker

  • February 16 – Tech to Improve On-Farm Efficiency

Manure On-the-Go Sensing, Chris Shoup

Yield Monitor Data, Alysa Gauci

Virtual Reality and Field Demonstrations, Brooke Beam

Equipment Technology, Andrew Klopfenstein

  • February 23 – eFields Small Grains, Forages, Soil Health, and Water Quality Results

Production Budgets and Custom Rates, Barry Ward

Winter Annual Forages, Jason Hartschuh

Barley Cohort, Eric Richer

Hemp, Lee Beers

Soil Health Testing, Boden Fisher

Registration for Ag Tech Tuesdays is free but required.  Just visit go.osu.edu/AgTechTues to register.  If you have any questions, please contact Elizabeth Hawkins (hawkins.301@osu.edu

 

Gibberella Ear Rot and Vomitoxin in Corn

Source: Dr. Pierce Paul, OSU

If your grain was harvested from a field with Gibberella ear rot (GER), it is more than likely contaminated with mycotoxins. Deoxynivalenol, also known as vomitoxin, is one of the mycotoxins most commonly produced by the fungus Fusarium graminearum that causes GER. Another name for this fungus is Gibberella zeae, hence the name of the disease. Before storing grain harvested from GER-affected fields or areas where conditions were favorable for the disease, pull a sample and test for the presence and level of contamination with vomitoxin. Mycotoxin tests are either qualitative, semi-quantitative, and quantitative. Qualitative tests provide a yes/no answer for the presence of the toxin and are useful for initial screening. Semi-quantitative tests estimate whether the toxin is at or above certain levels (>5 ppm) or within a given range, whereas quantitative tests provide more precise estimates of contamination. There is a trade-off between precision, price, and speed. Quantitative tests tend to be the most precise but are also more expensive and take longer to complete than the qualitative or semi-quantitative tests. Semi-quantitative quick-test kits are very common and relatively easy to use and inexpensive. They are often very specific for one particular toxin. A test developed specifically for Aflatoxin or Fumonisins will NOT work for vomitoxin.

Unfortunately, there are no commercially available treatments to reduce vomitoxin levels in stored grain.  Poor storage may cause toxin levels to increase. Warm, moist pockets in the grain promote mold development, causing the grain quality to deteriorate and toxin levels to increase. Aeration is important to keep the grain dry and cool. However, it should be noted that while cool temperatures, air circulation, and low moisture levels will minimize fungal growth and toxin production, these will not decrease the level of toxin that was already present in grain at the time of storage.

  • Dry and store harvested grain to below 15% moisture of lower to minimize further mold development and toxin contamination in storage.
  • Store dried grain at cool temperatures (36 to 44°F) in clean, dry bins. Moderate to high temperatures are favorable for fungal growth and toxin production.
  • Periodically check grain for mold, insects, and temperature.
  • If mold is found, send a grain sample for mold identification and analysis to determine if toxins are present and at what level.
  • Clean bins and storage units between grain lots to reduce cross-contamination.

Several companies sell test strips for mycotoxin analysis, including Romer Labs (http://www.romerlabs.com) and Neogen (http://www.neogen.com/). These tests are fairly easy to use once you read and follow the manufacturer’s guidelines carefully.

More information on sampling, testing, and storage can the found in factsheet # PLPATH-CER-04 (http://ohioline.osu.edu/factsheet/plpath-cer-04).