C.O.R.N. Newsletter: 2021-11
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Cold Weather Impact on Corn and Soybean
Imbibitional chilling may occur in corn and soybean seeds if the soil temperature is below 50°F when the seed imbibes (when seed rapidly takes up water from the soil, usually within 24 hours after planting). Imbibitional chilling can cause reductions in stand and seedling vigor. If seeds were planted into soil at least 50°F (and have already imbibed), the drop in temperature is not likely a problem if the plants have not yet emerged from the soil. This year, the concern is for seed planted into dry soil that imbibed due to the recent snow melt.
If your corn and soybean plants were emerged at the time of the cold temperatures last week, fields should be assessed this week as the temperature warms up. The growing point of corn is below the soil surface until the V6 growth stage, and therefore is protected from low temperatures to some extent. For soybean, the growing point is above the ground when the cotyledons are above the soil surface. If damage occurs below the cotyledons, the plant will die.
If your corn and soybean plants were not yet emerged at the time of the cold temperatures last week, you may need to wait longer to assess potential damage. Checking the seeds now may be hard to tell if imbibitional chilling occurred because affected seeds that won’t complete the germination process will still absorb water. As the temperatures warm up, corn and soybean seeds should begin to germinate and emerge from the soil. We suggest assessing corn and soybean stand as plants emerge.For soybeans planted in April or May, a stand as low as 100,000 plants per acre can still produce maximum yield. However, we do not recommend replanting until the soybean stand is less than 50,000 plants per acre. At low plant populations, soybean plants can compensate through increased branching (Figure 1). In our research, going from 100,000 plants per acre to 50,000 plants per acre resulted in a 9 to 14% reduction in yield.
Final stands for corn should be between 24,000 and 26,000 plants per acre in lower yielding environments to optimize yield, though some higher yielding environments maximize yield at stands that exceed 34,000 plants per acre. Early planting dates with lower stands can still produce exceptional yield. For example, in past research, a stand of 20,000 plants per acre planted on April 20 yielded 90% of the optimum. If stands are 15,000 plants per acre or fewer, a replant may be warranted as the yield gained from a higher seeding rate planted in early to mid-May can exceed the yield from corn with a low stand planted in mid-April.
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Challenges Ahead
There are challenges ahead so we will break them into short-term and long-term.
Short-term
The recent snow was a rare event for the amount that fell across Ohio. However, the minimum temperatures in the 20s and 30s was not that far off of normal for last freeze conditions for Ohio.
The strongest typhoon ever in the northern hemisphere occurred east of the Philippines last week and this energy will come across parts of North America over the next week. When that happens weather model performance often drops. Hence, if you see more bouncing around of forecasts the next 10-15 days that may be one reason why.
We have a big warm-up the first half of this week ahead of a strong storm that will move through Ohio the second half of the week with wind and rain. We could see anywhere from 0.50 inches to over 2 inches across Ohio later this week but placement is not certain and seems to favor central and southern Ohio with the highest amounts. Expect most places to see an inch or less given recent track record of events coming in lighter. Once the storm passes colder air will push in and some frost will be possible this weekend with lows in the 30s.
The rainfall the next 30-days is critical for the growing season as moderate drought over northern Ohio already has soil conditions in a shortage.
The latest drought monitor can be found here:
https://droughtmonitor.unl.edu
Also, some of the greatest evaporative demand in the country has been in parts of northern Ohio the last 30+ days and can be monitored as a leading indicator for drought development at this webpage via NOAA:
https://psl.noaa.gov/eddi/realtime_maps/images/latest.trim.png
You can keep up on the Ohio River Forecast Center's Water Resources Outlooks at:
https://www.weather.gov/ohrfc/WRO
Long-term
May appears will see periods of well above and below normal temperatures but will average out close to normal or just slightly above normal. Precipitation continues to trend at or below normal but models suggest a normal May for precipitation. If we get timely rains that will help soil conditions for summer. If we miss critical rains in May, this could lead to summer issues.
The latest rainfall outlook for the next 16-days is viewable in the attached image. Normal rainfall is nearing 2 inches for the next 16-days. We expect 1-3 inches for most areas.
For summer, most climate models indicate above normal temperatures and medium to high confidence of above normal temperatures during typical peak temperatures from mid-June to mid-August. We will need to monitor this. Confidence in summer rainfall is low. Most outlooks and models suggest not too far from normal rainfall but the reality is since 30-50% of summer rainfall comes from local soils, the next 30-days will be a big player in our summer rainfall outcome.
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CFAES Ag Weather System 2021 Near-Surface Air and Soil Temperatures/Moisture
A very unusual late season snowfall and three nights near or below freezing led to a significant drop in daily average soil temperatures by mid-week last week (Fig. 1). Most locations fell below 50°F with our northeast site in Ashtabula County dropping below 40°F. Temperatures recovered some throughout the weekend, as two- and four-inch soil temperatures are now at or slightly cooler than this time last week, running in the upper 40s to low 50s. This week will feature a significant warm up for the first half of the week, with maximum air temperatures reaching the upper 70s to low 80s for much of Ohio on Tuesday. Slightly cooler temperatures will occur for Wednesday and Thursday with rain expected, then chillier air temperatures, in the 50s and 60s, along with some morning patchy frost are possible for the weekend
A solid swath of 3-6” of snow fell with last week’s storm along with some light to moderate rain on Saturday. Still, much of the state fell short of typical weekly averages for this time of year. Figure 2 (left) shows that precipitation was generally 0.50” or less across most of the state. Overall, Ohio remains dry, especially across our northern counties, even to depths of 40 cm (Fig. 2-right). The U.S. Drought Monitor currently shows approximately 46% of the state is at least abnormally dry, with 22% in Moderate Drought conditions.
For more complete weather records for CFAES research stations, including temperature, precipitation, growing degree days, and other useful weather observations, please visit https://www.oardc.ohio-state.edu/weather1/.
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Overholt Drainage Workshop
Join OSU Extension for a webinar focused on drainage design, installation, and management including updates on on recently passed H.B. 340 – Ohio’s “petition ditch laws” that address the installation and maintenance of drainage works of improvement in Ohio. A panel of professional engineers representing state and federal agencies, drainage contractors, and tile manufacturers will discuss some standard practices, common issues, and troubleshooting associated with drainage design, installation, and repairs.
2021 Overholt Drainage Workshop
Drainage planning, design, installation, and management
Wednesday, June 9, 2021 9AM to 12 Noon
Registration: No cost to attend. Registration required. (Register Here)
Or visit: https://go.osu.edu/drainageschool
CEU credits available for CCAs and Professional Engineers
AGENDA
How drainage design affects crop yield and economics?
Larry Brown, Professor and Extension Agricultural Engineer, The Ohio State University
Drainage law – recent updates to Ohio Drainage Law
Peggy Kirk Hall, Field Specialist, Agriculture and Resource Law, The Ohio State University
Designing drainage & associated practices - standards and good practices for design
Justin McBride, Ohio Dept. of Ag.
Installing drainage & associated practices (safety, standards, and good practices for installation)
Bob Clark II, Clark Farm Drainage, inc., New Castle, IN
When drainage goes wrong: Drainage design & installation Panel
Moderator: Paul Chester, Retired NRCS Engineer
Panelists: Justin McBride and Mark Seger, Ohio Dept. of Ag.
Greg Wells, Ohio NRCS; Bob Clark II, NLICA
Steve Gerten, Rick Galehouse, and Dave Schweiterman, OLICA
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Yes, Another Article About Freeze Symptoms in Winter Wheat
After a (short) second round of winter last week, there has been some concern regarding winter wheat. As a reminder, the magnitude of freeze damage depends on: 1) temperature, 2) duration of
temperature, and 3) wheat growth stage. During the cold snap last week, the majority of winter wheat in Ohio was at the Feekes 6 to 8 growth stage. In northern Ohio, temperatures were in the low 30s to upper 20s. In Southern Ohio, temperatures were mostly above 30°F with a dip to 26°F on April 23, recorded by the CFAES weather system in Pike County. Underneath the snow, temperatures were warmer (Figure 1 records the temperature under the snow on April 21). A few years ago, we conducted a freeze chamber experiment to examine the effect of low temperature on winter wheat at several growth stages (Table 1). Keep in mind, actual yield reductions in the field can be quite variable depending on the weather for the remainder of the growing season. At Feekes 6 growth stage, temperatures >20°F caused no damage. However, by Feekes 8 growth stage, temperatures of 25°F to 28°F caused a 10 to 25% reduction in wheat yield. These temperatures were from the crown of the wheat plant, not air temperature.
What to look for: After a freeze event, wait one to two weeks after active growing conditions resume to check for visual signs of freeze injury. Make sure to examine several areas of the field as landscape features influence the micro-climates within fields. Small differences in temperatures can cause large differences in damage and grain yield.
At Feekes 6 growth stage, damage from freezing will cause discoloration of the leaf tissue, with leaf tips or edges exhibiting symptoms first (Figure 2). However, discoloration does not necessarily indicate a reduction in grain yield. At Feekes 6 growth stage, damage can also be assessed by carefully cutting the wheat stem lengthwise to expose the developing spike at the first node. Damaged spikes will appear discolored and shriveled. A healthy, developing spike should be rigid and whitish-green (Figure 3).
At Feekes 8 growth stage, damage from freeze may include yellowing or browning of the flag leaf. The flag leaf may appear twisted or in a spiral (Figure 4). As the plant continues to grow, the wheat spike may get stuck in the leaf sheath, causing a crooked appearance at heading (Figure 5). (Although, this phenology can also be associated with spikes that emerge quickly due to warm temperatures.)
Overall, I think freeze damage should be minimal from this most recent cold snap. At Feekes 6 growth stage, wheat is still fairly tolerant of cold temperatures. In the southern portion of the state, where wheat stage was more advanced, temperatures tended to be warmer. However, the best way to assess for potential damage is to scout your field after active growing conditions resume this week. For more information, see our new ‘Freeze Symptoms and Associated Yield Loss in Soft Red Winter Wheat’ FactSheet: https://ohioline.osu.edu/factsheet/anr-93
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
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 an accessible format of this publication, visit cfaes.osu.edu/accessibility.