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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Weather Update from NOAA/NWS/Ohio River Forecast Center

Source: Jim Noel, NOAA

The climate pattern is in a state of a flux.  The La Nina pattern is weakening rapidly and will cause changes in weather patterns in the coming weeks and will result in lower confidence forecasting for a while during this change.

For April it looks like a warmer than normal month with normal or slightly below normal rainfall. However, there will still be big swings in temperatures so the last freeze will likely be in the normal range which is generally mid-April for southern Ohio to late April for northern Ohio.  Evaporation rates will be above normal. This will all result in typical or earlier than normal planting. Beneficial rains will fall over most of the corn and soybean belts in April with the least rain likely in the eastern areas including Ohio. Over the next two weeks we expect 0.50 to 2 inches of rain with normal rainfall being 1.5 to just under 2 inches. Hence rainfall is forecast the next two weeks to be 50-100% of normal.

Soil moisture is in good shape in southern Ohio but is short in northern Ohio and needs to be watched carefully. Soil moisture will improve in most of the corn and soybean belts in April especially in the western half of the region which needs it. However, soil conditions in Ohio will likely stay the same or get a bit drier in April with above normal temperatures, above normal evapotranspiration rates and normal to below normal rainfall.

You can get all the latest information from the NOAA/NWS/Ohio River Forecast Center on drought risk here: https://www.weather.gov/ohrfc/DroughtBriefing

Seasonal information can be found here: https://www.weather.gov/ohrfc/SeasonalBriefing

The outlook during the growing season from May through summer looks like a warmer to hotter than normal summer. It is not clear whether this will be more of a consistent warm of whether it will be more of an impact to maximum temperatures above 95. We will keep you posted on that.

Rainfall confidence from May through summer is quite uncertain. With La Nina weakening that could offset some of the risk to the drier side. Hence, at this time the outlook supports normal to slightly drier than normal. In the summer 30-50% of rainfall comes from local soil moisture so it is important to watch your local soil moisture between now and Memorial Day as it will be a big driver in summer rains. Bottomline, we are aware there is some risk for growing drought risk into summer but confidence is still low in the outcome.

https://www.cpc.ncep.noaa.gov/products/predictions/long_range/poe_index.php?lead=4&var=p

In summary, the tendency supports warmer weather overall through the planting and growing season with rainfall normal to below normal. There is some risk of expanding drought but confidence in that remains low at this time.

Reminder! Register for Precision University Today

Source:  John Barker, Amanda Douridas, Ken Ford, John Fulton, Mary Griffith, Will Hamman, Elizabeth Hawkins

Tackling Spring Operations with Reduced Working Days

January 5, the first virtual Precision University event, is quickly approaching. Be sure to register today so you do not miss out on important information to help you improve spring performance. The 2021 focus is “Tackling Spring Operations with Reduced Working Days.” Speakers from around the country will share their research and experience centered on the challenges farmers face during spring with changing weather patterns.

January 5 – Gambling with Planting Decisions – Dr. Aaron Wilson (Ohio State University Extension) and Dr. Bob Nielsen (Purdue University). 1 CCA CM Credit.

January 12 – Improving Fertilizer Efficiency with the Planter Pass – Matt Bennett (Precision Planting Technology) and Dr. John Fulton (Ohio State University). 1 CCA PAg Credit

January 19 – Pre-season Crop Protection Decisions – Dr. Mark Loux and Dr. Scott Shearer (Ohio State University). 0.5 CCA PM and 0.5 PAg Credits.

January 26 – Sprayer Technology to Improve Field Performance – Dr. Joe Luck (University of Nebraska-Lincoln). 1 CCA PAg Credit.

There is no cost to attend Precision University, but registration is required. For more information or to register, visit http://go.osu.edu/PrecisionU. If you have any questions about the Precision U sessions, please feel free to contact Amanda Douridas (Douridas.9@osu.edu).

 

Do Not Plant These Seeds!!!

The Ohio Department of Agriculture (ODA) has been notified that several Ohio residents have received unsolicited packages containing seeds that appear to have originated from China. The types of seeds in the packages are currently unknown. The packages were sent by mail and may have Chinese writing on them. Unsolicited packages of seeds have been received by people in several other states across the United States over the last several days.

If you receive a package of this type, please DO NOT plant these seeds. If they are in sealed packaging, don’t open the sealed package. Please retain the seeds and the original package labeling for trade compliance officers as they work through this issue. Unsolicited seeds could be invasive species, contain noxious weeds, could introduce diseases to local plants, or could be harmful to livestock. Invasive species and noxious weeds can displace native plants and increase costs of food production. ODA and APHIS work hard to prevent the introduction of invasive species and protect Ohio agriculture. All foreign seeds shipped to the United States should have a phytosanitary certificate which guarantees the seeds meet important requirements.

Recommendations for Soybeans Planted in June

Source: Laura Lindsey, The Ohio State University

While progress is way ahead of last year, soybean planting is spilling into June. (According to USDA NASS, 53% of soybean acreage was planted by May 24, 2020. Last year, at the same time, only 11% of soybean acreage was planted.) As planting continues into June, farmers may want to consider adjusting their cultural practices:

Row spacing. Soybean planted in narrow rows (7.5 or 15-inch row width) generally yields higher than soybean planted in wide rows (30-inch). The row spacing for June-planted soybeans should be 7.5 to 15 inches, if possible. Row width should be narrow enough for the soybean canopy to completely cover the interrow space by the time the soybean plants begin to flower. The later in the growing season soybeans are planted, the higher the yield increase due to narrow rows.

Seeding rate. Higher seeding rates are recommended for June planting dates. The final (harvest) population for soybean planted in June should be 130,000 to 150,000 plants/acre. (For May planting dates, a final stand of 100,000 to 120,000 plants/acre is generally adequate.)

Relative maturity. Plant the latest maturity variety that will reach physiological maturity before the first killing frost. This is to allow the plants to grow vegetatively as long as possible to produce nodes where pods can form before vegetative growth is slowed due to flowering and pod formation. The recommended relative maturity ranges are shown in the table below.