C.O.R.N. Newsletter: 2020-36
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First Widespread Freeze Arrives; Wetter Pattern Sets In
Much of Ohio experienced frost or freeze conditions this past Friday and/or Saturday night. In fact, many locations dropped below 30°F (Table 1), with unofficial observations as cold as 26°F! How does this compare to typical first freeze dates?
Figure 1 shows the climatological median date (50th percentile; 1980-2010) occurrence for the first 32°F in the fall. Ohio’s dates vary widely, as early as the last week in September in some of the colder valleys of the northeast hills (light blue) to as late as the first week of November (brown) in the far east. However, much of Ohio experiences first freeze during the second and third weeks of October. So, this year’s first freeze appears to be right on schedule across the north and a bit early for areas of southern and southwest Ohio.
Forecast
A stalled boundary is currently draped across Ohio. This boundary is providing a focus for shower activity, bringing the heaviest widespread rainfall that we have seen in Ohio since Labor Day. CoCoRaHS observations show that 0.5-1.25” of rain has fallen in the last 24 hours, with additional rain showers expected Monday night into Tuesday morning. This frontal boundary will lift north of the region by Wednesday afternoon, but not before providing the opportunity for additional showers through Wednesday morning. Highs will warm into the mid to upper 70s for mid to late week, perhaps even low 80s across the south on Thursday, with dry conditions expected through Friday morning. A strong cold front will approach the region on Friday, bringing a line of showers and storms through late in the day. Behind this front, much cooler air will filter back into the region, with highs in the 50s and 60s and overnight lows in the 30s and 40s expected this weekend. The weekend should remain dry before damp, chilly conditions return early next week. The Weather Prediction Center is currently forecasting 0.50-1.25” of rain across most of Ohio for the next 7 days, with greatest totals in the far southwestern counties (Fig. 2).
The latest NOAA/NWS/Climate Prediction Center outlook for the 8-14 day period (October 27 – November 2) shows below average temperatures and above average precipitation are likely (Fig. 3). Normal highs during the period are in the upper-50s to low-60s, lows in the upper-30s to low-40s, with about 0.85” of rainfall per week.
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Extended Drydown in Corn
As fall is progressing, crop harvest is also occurring throughout the state. However, many producers are seeing slower than usual drydown in their corn fields this October. This may be in part due to how the weather conditions impacted corn growth and development this year.
In many parts of Ohio in 2020, temperatures were near the long-term average this season. One marked difference though was that precipitation was below normal for much of the season around the state. In the table below, I have shown 2020 weather progression compared to that of 2018 at the Western Agricultural Research Station, specifically highlighting average temperature and accumulated precipitation.
In 2018 and 2020, temperatures were very similar to one another in each month, with the exception of May being slightly cooler and September being slightly warmer in 2020. The only month in which 2020 received more precipitation than in 2018 was May. Cool wet conditions resulted in planting dates that extended into the latter part of May for the state (USDA reported 57% corn acres planted on May 17 2020), but also may have contributed to delayed emergence due to slow heat unit accumulation (only 11% of the corn was emerged on May 17). Wet conditions following planting may have also contributed to poorer root development in 2020. Poor root development may have impacted corn’s ability to access soil nitrogen and soil moisture once precipitation levels dropped as well.
In 2020, rainfall in June-September was substantially less than in 2018. As a result, the corn crop may have experienced a sort of “delayed development” this year. Temperatures were below the long-term average, which may have contributed to the crop not exhibiting strong stress symptomology as one might expect when moisture levels are low. Rather, the crop may have been able to extend its growth phase to utilize the precipitation that did occur in August and September this year. For example, at the Western Agricultural Research Station in 2020 only 8 days in July registered precipitation greater than 0.05”, with four of those experiencing at least 0.25”. In August, 10 days were recorded with precipitation greater than 0.05”, but only two of these exceeded 0.25”.
As long as leaves and stalks above the ear remained intact, the crop may have been able to extend the grainfill period beyond what was expected based on growing degree day accumulation. Corn ears achieve approximately 50% of their grain yield prior to entering the R5 or dent growth stage. An additional 40% of yield is gained during the first half of the R5 growth stage. Given the later rain events paired with moderate temperatures, plants may have extended the R5 phase beyond what occurs in a normal year. Application of a strobilurin fungicide has been shown in past work to delay senescence in some environments, which could also delay corn drydown if conditions were favorable for this to occur.
A similar phenomenon related to an extended corn drydown phase was also observed in 2019 in Indiana (Nielsen, 2019) and in Michigan (M. Singh, personal communication) where corn drydown was progressing slower than expected given the GDD accumulation. In the case of 2019, this was suspected to be in part to delayed planting. By May 31, 80% of corn acres in Ohio had been planted in 2020 with 55% of the acres emerged. Given later planting progress in Ohio, this may also hold true for 2020 in that black layer was achieved later than usual in the state given the crop was utilizing late-season precipitation to complete the grain fill process.
Once the corn crop reaches physiological maturity (or kernel black layer), grain moisture content is approximately 35%. Under favorable conditions (warm, sunny, and breezy), grain moisture content can decrease by 0.75-1.0 percentage point per day. Recent work from Iowa State suggests grain drydown is approximately 0.7% per day in the first 20 days after physiological maturity, but drops to 0.44% per day after that point. In general, accumulation of 20 to 29 GDDs is required for grain moisture to lower 1%. However, as the weather turns cooler and potentially cloudier, the grain moisture content reductions will likely be lower, ranging from 0.0-0.5% per day. If temperatures remain warm in October, it is possible more grain drydown will occur as well. Agronomists recommend starting harvest when grain moisture content drops below 25%, and producers may need to plan on moisture levels being a little higher this year to accommodate a timely crop harvest.
References:
R. Martinez-Feria, M. Licht, and S. Archontoulis. 2017. Corn grain dry down in field from maturity to harvest. https://crops.extension.iastate.edu/cropnews/2017/09/corn-grain-dry-down-field-maturity-harvest
R.L. Nielsen. 2019. Late Planted Corn Not Maturing as Expected. https://www.agry.purdue.edu/ext/corn/news/articles_19/LatePlantedCornMaturity_1012.html
M. Singh and K. Cassida. 2019. Management guidelines for immature and frosted corn silage. https://www.canr.msu.edu/news/management-guidelines-for-immature-and-frosted-corn-silage
P. Thomison. 2019. Drydown in Corn: What to Expect? https://u.osu.edu/henryag/2019/10/01/drydown-in-corn-what-to-expect/
USDA-NASS. 2020. Crop Progress. https://usda.library.cornell.edu/concern/publications/8336h188j?locale=en#release-items
K. Wise and D. Mueller. 2011. Are fungicides no longer just for fungi? An analysis of foliar fungicide use in corn. https://www.apsnet.org/edcenter/apsnetfeatures/Pages/fungicide.aspx
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Stalk Rots Showing Up in Some Corn Fields
Corn harvest is progressing very slowly across the state as the crop is taking unusually long to dry down this year. The longer the crop stays in the field, there greater the risk of late-season diseases such as ear and stalk rots, especially if it continues to rain. Stalk rot often refers to a combination of several interrelated problems, including stalk breakage, stalk lodging, premature plant death, and root lodging. Several factors may contribute to stalk rot, including extreme weather conditions, inadequate fertilization, problems with nutrient uptake, insects, and diseases. For instance, when leaves above the ear are severely damaged (either by diseases, insects, or some environmental stress) well before grain-fill is complete, the plants often translocate sugars from the stalk to fill grain, causing them to become weak and predisposed to fungal infection. A number of fungal pathogens cause stalk rot, but the three most important in Ohio are Gibberella, Collectotrichum (anthracnose), and Fusarium.
Losses due to stalk rot vary from field to field and from one hybrid to another. Stalk rots may cause lodging, especially if the affected crop is not harvested promptly. However, it is not uncommon to walk corn fields where nearly every plant is upright yet nearly every plant is also showing stalk rot symptoms. Many hybrids have excellent rind strength, which contributes to plant standability even when the internal plant tissue has rotted or started to rot. However, strong rinds will not prevent lodging if harvest is delayed and the crop is subjected to weathering, e.g. strong winds and heavy rains.
A symptom common to all stalk rots is the deterioration of the inner stalk tissues so that one or more of the inner nodes can easily be compressed when squeezed between thumb and finger. It is possible by using this "squeeze test" to assess potential lodging. The "push" test is another way to predict lodging. Push the stalks at the ear level, 6 to 8 inches from the vertical. If the stalk breaks between the ear and the lowest node, stalk rot is usually present. To minimize stalk rot damage, harvest promptly after physiological maturity, even if you have to do so at a slightly higher moisture content (moisture in the lower 20s). Harvest delays will increase the risk of stalk lodging and grain yield losses, and slowdown the harvest operation. In addition, lodging may lead to ear rots and grain contamination with mycotoxins as ears come into contact with the soil and crop residue.
This is an updated version of a previous article by Pierce Paul and Peter Thomison
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2020 Ohio Soybean Performance Trial: Henry County and Preble County Yield Results Available
Henry County and Preble County results of the 2020 Ohio Soybean Performance Trials are available online here: https://stepupsoy.osu.edu/news/ohio-soybean-performance-trials-henry-co-and-preble-co-yield-results Results from the other trial locations will be added as harvest and data analysis continues.
In the early trial (RM 1.9 to 3.1) at Henry County, yield ranged from 46.4 to 56.5 bu/acre (average 51.4 bu/acre). In the late trial (RM 3.2 to 3.9) at Henry County, yield ranged from 44.5 to 57.4 bu/acre (average 50.0 bu/acre).
In the early trial (RM 2.5 to 3.6) at Preble County, yield ranged from 54.4 to 80.9 bu/acre (average 70.2 bu/acre). In the late trial (RM 3.7 to 4.4) at Preble County, yield ranged from 53.1 to 86.7 bu/acre (average 72.3 bu/acre).
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.
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