Stalk Quality Concerns

Source: Peter Thomison, Pierce Paul, OSU Extension

2019 may be an especially challenging year for corn stalk quality in Ohio. Stress conditions increase the potential for stalk rot that often leads to stalk lodging (Fig. 1).  This year persistent rains through June caused unprecedented planting delays. Saturated soils resulted in shallow root systems. Corn plantings in wet soils often resulted in surface and in-furrow compaction further restricting root growth. Since July, limited rainfall in much of the state has stressed corn and marginal root systems have predisposed corn to greater water stress.

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Corn Grain Test Weight

Source: R.L. Nielsen, Purdue Univ. (edited)

Among the top 10 most discussed (and cussed) topics at the Chat ‘n Chew Cafe during corn harvest season is the grain test weight being reported from corn fields in the neighborhood. Test weight is measured in the U.S. in terms of pounds of grain per volumetric “Winchester” bushel. In practice, test weight measurements are based on the weight of grain that fills a quart container (37.24 qts to a bushel) that meets the specifications of the USDA-FGIS (GIPSA) for official inspection (Fig. 1). Certain electronic moisture meters, like the Dickey-John GAC, estimate test weight based on a smaller-volume cup. These test weight estimates are reasonably accurate but are not accepted for official grain trading purposes.

The official minimum allowable test weight in the U.S. for No. 1 yellow corn is 56 lbs/bu and for No. 2 yellow corn is 54 lbs/bu (USDA-GIPSA, 1996). Corn grain in the U.S. is marketed on the basis of a 56-lb “bushel” regardless of test weight. Even though grain moisture is not part of the U.S. standards for corn, grain buyers pay on the basis of “dry” bushels (15 to 15.5% grain moisture content) or discount the market price to account for the drying expenses they expect to incur handling wetter corn grain.

Growers worry about low test weight because local grain buyers often discount their market bids for low test weight grain. In addition, growers are naturally disappointed when they deliver a 1000 bushel (volumetric bushels, that is) semi-load of grain that averages 52-lb test weight because they only get paid for 929 56-lb “market” bushels (52,000 lbs ÷ 56 lbs/bu) PLUS they receive a discounted price for the low test weight grain. On the other hand, high test weight grain makes growers feel good when they deliver a 1000 bushel semi-load of grain that averages 60 lb test weight because they will get paid for 1071 56-lb “market” bushels (60,000 lbs ÷ 56 lbs/bu).

These emotions encourage the belief that high test weight grain (lbs of dry matter per volumetric bushel) is associated with high grain yields (lbs. of dry matter per acre) and vice versa. However, there is little evidence in the research literature that grain test weight is strongly related to grain yield.

Hybrid variability exists for grain test weight, but does not automatically correspond to differences in genetic yield potential. Grain test weight for a given hybrid often varies from field to field or year to year, but does not automatically correspond to the overall yield level of an environment.

Similarly, grain from high yielding fields does not necessarily have higher test weight than that from lower yielding fields. In fact, test weight of grain harvested from severely stressed fields is occasionally higher than that of grain from non-stressed fields, as evidenced in Fig. 2 for 27 corn hybrids grown at 3 locations with widely varying yield levels in Kansas in 2011. Another example from Ohio with 22 hybrids grown in common in the drought year of 2012 and the much better yielding year of 2013 also indicated no relationship between yield level and grain test weight (Fig. 3).

Conventional dogma suggests that low test weight corn grain decreases the processing efficiency and quality of processed end-use products like corn starch (U.S. Grains Council, 2018), although the research literature does not consistently support this belief. Similarly, low test corn grain is often thought to be inferior for animal feed quality, although again the research literature does not support this belief (Rusche, 2012Simpson, 2000Wiechenthal Pas et al., 1998). Whether or not low test weight grain is inferior to higher test weight grain may depend on the cause of the low test weight in the first place.

Common Causes of Low Grain Test Weight

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Will Late Planted Corn Reach Black Layer Before a Killing Frost?

Source:  Allen Geyer, Rich Minyo, Peter Thomison, OSU

Early morning frost on corn Source: Purdue Univ.

Ohio saw record late corn planting in 2019.  According to the Agricultural Statistics Service, only 33% of Ohio’s corn was planted by June 2.  The question being asked now is will the June planted corn reach physiological maturity (black layer) before a killing frost?  Corn is killed when temperatures are near 32°F for a few hours and when temperatures are near 28°F for a few minutes.

A useful tool is available from the Midwestern Regional Climate Center (the U2U tool, available at:  https://mrcc.illinois.edu/U2U/gdd/) that uses current and historical weather data to predict when corn will reach black layer.  The user selects the geographic location that they are interested in, actual planting date and the adjusted relative maturity of the planted hybrid.

Previous studies have indicated that the GDD requirement of late planted corn to reach black layer from planting is less than the requirement of corn planted on a “normal” date.  Keeping this in mind, Dr. Bob Nielsen from Purdue University has developed an adjustment to the GDD requirements for late planted corn.  This calculator can be found at:  https://www.agry.purdue.edu/ext/corn/news/timeless/hybridmaturitydelayedplant.html  Using this calculator, enter the adjusted GDD value in the U2U tool in the “Black Layer GDDs” line.

We have used the U2U tool to predict whether our corn research will accumulate enough GDDs before a killing frost.  Table 1 shows the results of using these tools for the 2019 Ohio Corn Performance Test sites (OCPT) as well as a late planted demo plot that was planted at Hoytville.  These results are based on a 109-day (2618 GDD) hybrid.  The table indicates the planting date, adjusted GDD requirement for the 109 day hybrid, whether physiological maturity (black layer) will be achieved before frost, the predicted black layer date and the average 32° and 28° frost dates.  Because of the adjusted GDD requirements with later planting dates, the predicted GDD accumulations will exceed or just meet the required GDDs before the average frost date for all 10 OCPT sites, including the 5 sites that were planted in June.  We hope that these predictions come true!  Note that the demo plots at Hoytville that were planted on June 27 will not reach black layer before a killing frost based on the U2U tool.

Table 1.  Planting date, Adjusted Hybrid GDD Requirement, Reach BL Before Frost, Predicted Black Layer (BL) Date, and Average Frost Dates for 2019 Ohio Corn Performance Test sites.

 

Considerations for 2019 Wheat Planting

Source: Andy Michel, Laura Lindsey, Pierce Paul, OSU

With the autumn rapidly approaching, wheat planting is likely to begin soon. Planting after the Hessian fly free date remains the best chance to avoid issues with insects and diseases, as well as helping ensure good agronomic quality.  Some benefits of the fly free date:

Hessian Fly: Adults of the Hessian fly lay eggs in emerging wheat. These eggs then hatch into small larvae that feed before spending the winter as a flaxseed. The early autumn feeding will stress the young wheat plant right before the winter, resulting in stunted and wilted plants.  Very little egg laying occurs after the fly free date, which helps to limit infestation. Wheat varieties with resistance against the Hessian are available, in addition to seed treatments, which can help limit damage.

Aphids: Two main aphids infest wheat in Ohio: the English grain aphid and the bird cherry-oat aphid.  These aphids rarely cause economic injury on wheat from feeding. However, they can transmit several viruses that can severely impact wheat including Barley Yellow Dwarf virus.  These aphids do not only feed on wheat, but several other grasses that serve as natural sources of viruses.  If wheat is planted too early, and emerges before the aphids overwinter or stop feeding, they can be early transmitters of viruses.  Although seed treatments could help kill the aphids, they may survive long enough to transmit the virus to the plant.  Any transmission in the autumn would likely serve as a local source in the following spring.

Other foliar diseases: Although not directly related to the Hessian Fly, planting after the fly free date also helps to reduce the early establishment of leaf diseases like Stagonospora leaf blotch and powdery mildew. Planting date is indirectly linked to spore production by fungi that cause these diseases and infection of young plants. The earlier you plant, the more spores are available, and the more suitable (warmer) conditions are for infection. Fall infections often leads to more damage and greater yield loss in the spring, especially of susceptible varieties are planted and not protected with a fungicide at Feeks 8 (flag leaf emergence). As conditions become cooler after the fly free date, pathogens that cause leaf diseases become last active, and as such, are less likely to infect plants.

Drydown In Corn – What To Expect?

Source: Dr. Peter Thomison, OSU

Many corn growers may encounter slower than normal drydown this fall due to late crop development associated with June planting dates. Much of Ohio’s late-planted corn may not achieve black layer until mid-October or later when drying conditions are less favorable for drydown.  Once corn achieves physiological maturity (when kernels have obtained maximum dry weight and black layer has formed), it will normally dry approximately 3/4 to 1% per day during favorable drying weather (sunny and breezy) during the early warmer part of the harvest season from mid‑September through late September. By early to mid‑October, dry-down rates will usually drop to ½ to 3/4% per day. By late October to early November, field dry‑down rates will usually drop to 1/4 to 1/2% per day and by mid-November, probably zero to 1/4% per day. By late November, drying rates will be negligible.

Estimating dry‑down rates can also be considered in terms of Growing Degree Days (GDDs). Generally, it takes about 30 GDDs to lower grain moisture each point from 30% down to 25%. Drying from 25 to 20 percent requires about 45 GDDs per point of moisture. In October, we typically accumulate about 5 to 10 GDDs per day. However, note that the above estimates are based on generalizations, and it is likely that some hybrids may vary from this pattern of drydown. Some seed companies indicate considerably lower GDDs for grain moisture loss, i.e. 15 to 20 GDDs to lower grain moisture each point from 30% down to 25% and 20 to 30 GDDs per point from 25% to 20%.

Past Ohio research evaluating corn drydown provides insight on effects of weather conditions on grain drying. During a warm, dry fall, grain moisture loss per day ranged from 0.76 to 0.92%. During a cool, wet fall, grain moisture loss per day ranged from 0.32 to 0.35%. Grain moisture losses based on GDDs ranged from 24 to 29 GDDs per percentage point of moisture (i.e., a loss of one percentage point of grain moisture per 24 to 29 GDDs) under warm dry fall conditions, whereas under cool wet fall conditions, moisture loss ranged from 20 to 22 GDDs. The number of GDDs associated with grain moisture loss was lower under cool, wet conditions than under warm, dry conditions.

Weather related crop stress may affect drydown this year. Dr. Bob Nielsen at Purdue University notes, “When areas of fields die prematurely due to stresses like drought, spatial variability for grain moisture at harvest can be dramatic and often creates challenges with the management of the grain dryer operation. This is especially true early in the harvest season when grain moistures of healthier areas of the field are in the low 20’s. The spatial variability for grain moisture decreases later in the harvest season as grain moistures throughout the field settle to an equilibrium level (15% or less).”

Agronomists generally recommend that harvesting corn for dry grain storage should begin at about 24 to 25% grain moisture. Allowing corn to field dry below 20% risks yield losses from stalk lodging, ear drop, ear rots, insect feeding damage and wildlife damage.

For more on grain drydown, check out the following article by Dr. Nielsen.

Nielsen, R.L. 2018. Field Drydown of Mature Corn Grain. Corny News Network, Purdue Univ.
URL: http://www.kingcorn.org/news/timeless/GrainDrying.html [URL accessed Sept. 23, 2019].

Above normal temperatures will continue for the rest of September

Source: Jim Noel

After a cooler start to September it was expected to be warmer than average and that has happened and will last the rest of the month. Highs will generally be in the 70’s and 80’s north half and in the upper 70’s to near 90 range in the south half. Lows will generally be in the 50s and 60s. This will be several degrees above normal.

The first half of September was expected to be drier with a trend to normal or wetter weather in later September. Indications are that we will remain at or below normal rainfall for most of the state for the remainder of September. Over the next two weeks, rainfall is forecast to be mainly an inch or less with normal being 1.0-1.5 inches. The main rain areas will be off the southeast U.S. coast and in the upper Midwest as the attached two week rainfall graphic shows. High pressure will remain in control of a good portion of the southeast third of the U.S. as tropical activity off the U.S. Southeast Coast will help strengthen the high pressure in the Southeast.

Probabilities support our first first freeze at or later than normal for this autumn. Typically it occurs in the Oct. 10-20 range for much of the state. It is highly unlikely we will see anything before Oct. 10.

Looking at October, we expected near to slightly above normal and rainfall not too far from normal.

Assessing The Risk of Frost Injury to Late Planted Corn

Source:  Peter Thomison, OSU

Lately I have received questions as to whether corn at various stages of development, especially the blister (R2) and dough (R4) stages, will mature before the 50% average frost date. According to the National Agricultural Statistics Service, as of August 18, 37 percent of Ohio’s corn acreage was in the dough stage (R4) compared to 70 percent for the five year average, and three percent of the corn acreage was in the dent stage (R5) compared to 21 percent for the five-year average. Many areas of the state corn are considerably behind the five-year average because of late planting. Late 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.

Physiological maturity (R6), 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 has summarized research findings from Purdue University and Ohio State University 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 mid-June. The calendar days and thermal time from silking to black layer for the 111-day hybrid maturity are shown in Table 1 from http://www.agry.purdue.edu/ext/corn/news/timeless/RStagePrediction.html. The calendar days and thermal time from silking to black layer for the 97-day hybrid and 105 maturity are also available from this Purdue webpage.

Table 1

The study indicated that corn planted in mid-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 a 111-day hybrid planted in mid-June?  To answer this question, estimate the expected GDD accumulation from Aug. 19 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 GDDs 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 GDDs required to achieve black layer depending on the corn’s developmental stage.

Table 2. Estimated GDDs remaining from Aug. 9 to the first fall frost for Ohio.

 

 

Region

Median Frost Date

(50% probability)

Estimated GDDs Remaining

From Aug. 19 to Fall Frost

Northwest Oct 10 – Oct 20 673 – 723
North Central Oct 10 – Oct 25 656 – 741
Northeast Sept 30 – Oct 25 603 – 749
West Central Oct 10 – Oct 15 716 – 773
Central Oct 5 – Oct 15 670 – 796
East Central Sept 30 – Oct 15 645 – 763
Southwest Oct 10 – Oct 15 752 – 815
South Central Oct 15 – Oct 20 841 – 893
Southeast Oct 5 – Oct 15 651 – 774

If your corn is in the milk stage (R3) as of Aug. 19, will it be safe from frost? Table 1 indicates that corn planted in mid – June required about 681 GDDs to reach black layer from R3 and Table 2 indicates that all regions of the state can accumulate that number of GDDs before the 50% frost date.

However, if your corn is in the blister stage (R2) as of Aug. 19, 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 R2 needs about 781 GDDs to reach black layer. Table 2 indicates that three regions of the state, South Central, Central, and Southwest, accumulate that number of GDDs before the 50% frost date. Several other regions, West Central, and Southeast, come close to accumulating this number whereas, the Northeast, Northwest, and North Central regions are least likely to accumulate the GDDs required to achieve physiological maturity.

The research results in Table 1 demonstrate 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, corn planted by mid-June has usually achieved physiological maturity before the first frost occurred.

Corn Growth & Development – R3 Milk

Today managing your corn crop requires knowledge of the different growth stages of the corn plant.  Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications.  Throughout the growing season I will discuss the various corn growth stages and management issue at each stage. 

R3 – Milk

The R3 (Milk) stage occurs about 18 – 22 days after silking.  At this stage the outside of the kernel is colored yellow while the inside is white.  The kernel contains a “milky” white fluid that will explode when pressure is applied.  Kernel moisture content is approximately 80% and starch is beginning to accumulate in the kernel.

Management/Scouting: Scout for drought symptoms.  Stress can still cause kernel abortions from the ear tip downward.  Insects: Corn Earworm, Corn Rootworm adults and Japanese Beetles Diseases: Eyespot, Gray Leaf Spot, Norther Leaf Blight, Southern Leaf Blight and Tar Spot

Photo Source: Corn Growth & Development, Iowa State University

Hot Night Temperatures Can Decrease Corn Yield

Source: Peter Thomison, Alexander Lindsey, OSU

Night time temperatures can affect corn yield potential. High night temperatures (in the 70s or 80s degrees F) can result in wasteful respiration and a lower net amount of dry matter accumulation in plants. Past studies reveal that above-average night temperatures during grainfill can reduce corn yield by reducing kernel number and kernel weight. The rate of respiration of plants increases rapidly as the temperature increases, approximately doubling for each 13 degree F increase. With high night temperatures more of the sugars produced by photosynthesis during the day are lost; less is available to fill developing kernels, thereby lowering potential grain yield. High night time temperatures result in faster heat unit or growing degree day (GDD) accumulation that can lead to earlier corn maturation, whereas cool night temperatures result in slower GDD accumulation that can lengthen grain filling and promote greater dry matter accumulation and grain yields.

The Pioneer Insight article referenced below concludes….

“Although higher night temperatures undoubtedly increase the rate of respiration in corn, research generally suggests that accelerated phenological development is likely the primary mechanism affecting corn yield.”

Research at the University of Illinois conducted back in the 1960’s indicated that corn grown at night temperatures in the mid-60s (degrees F) out yielded corn grown at temperatures in the mid-80s (degrees F). Average corn yields are generally much higher with irrigation in western states, which have low humidity and limited rainfall. While these areas are characterized by hot sunny days, night temperatures are often cooler than in the Eastern Corn Belt.  Low night temperatures during grain fill (which typically occurs in July and August) have been associated with some of our highest corn yields in Ohio. The cool night temperatures may have reduced respiration losses during grain fill and lengthened the rain fill period. Cooler than average night temperatures can also mitigate water stress and slow the development of foliar diseases and insect problems.

Corn Growth & Development – R2 Blister

Today managing your corn crop requires knowledge of the different growth stages of the corn plant.  Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications.  Throughout the growing season I will discuss the various corn growth stages and management issue at each stage. 

R2 – Blister

The R2 (blister) stage occurs about 10 – 12 days after silking.  At this stage the kernel is visible and resembles a blister.  The kernel is filled with clear fluid, the embryo is barely visible and it is at about 85% moisture.

Kernels are in a rapid period of grain-fill.  Rapid and steady grain-fill will continue through R6.  If severe stress occurs now or during R3, kernel abortion will occur from the tip of the ear downward.  Kernel abortion will continue until the plant has has enough carbohydrates for the remaining kernels.

Silks outside the husk leaves are drying and changing in color from tan to light brown.  The silks will naturally detach from their kernels following fertilization.