Weather
Central Ohio Agronomy School
Frost Damage to Soybeans
Source: Charles Hurburgh, Rebecca Vittetoe, Meaghan Anderson, Iowa State University
Figure 1. Frost-damaged soybeans with shriveled and discolored leaves. Photo courtesy of Rebecca Vittetoe.
Temperatures fell into the low 30’s and upper 20’s in most of Iowa over the weekend of October 11-13. Because of the very late planting season, some crops were immature enough to be injured by the freezing temperatures. This ICM Blog will address frost damage concerns to soybeans.
Frost normally forms early in the morning, driven by radiation cooling especially on clear cold nights. The visual impact of the frost damage is most evident the next day (Figure 1).
Temperatures below 32°F can damage soybean leaves, and temperatures below 30°F for an extended time periods can damage the stems, pods, and seeds. A killing freeze is considered to be 28°F for soybeans.
The severity of frost damage to soybeans depends on the following: how low the temperatures dropped, the duration of the cold temperatures, and the growth stage of the soybeans. Soybean fields with at least one mature pod on the main stem of each plant (R7 growth stage) are likely to be minimally affected by frost. Soybean plants with green pods will be more affected by frost. If the frost just damaged soybean leaves, particularly in the upper canopy, pods and seeds will continue to develop with yield minimally affected.
If the frost was more severe and damaged the stems, pods, and seed, the potential for reduced yield and quality is higher. In addition to reduced yield and quality, severely frost-damaged soybeans will dry down more slowly and be more likely to shatter at harvest. Farm moisture meters and older elevator meters will read about 1.5-2% points low until moisture and color have equalized. The new 150 mhz meters used by many elevators are more accurate.
Handling frost-damaged soybeans
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, 2012, Simpson, 2000, Wiechenthal 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
Late-season Frost Effects on Corn: Grain Production (Adapted from Dr. J. Lauer, Univ. of Wisconsin)
The following is information on the effects of late-season frost injury to corn from an article by Dr. Joe Lauer, Corn Extension Specialist at the University of Wisconsin (http://corn.agronomy.wisc.edu/Management/L041.aspx).
Freezing temperatures before physiological maturity will damage corn. Maturity in corn occurs when kernels form a black layer at the kernel tip, grain will be at approximately 30 to 35 percent moisture. After maturity, no additional dry matter will be accumulated in the seed. In addition to creating quality problems, premature frost will reduce the yield of dry grain.
Temperatures required to kill corn plants
Corn is killed when temperatures are near 32 F for a few hours, and when temperatures are near 28 F for a few minutes (Carter and Hesterman, 1990). A damaging frost can occur when temperatures are slightly above 32 F and conditions are optimum for rapid heat loss from the leaves to the atmosphere, i.e. clear skies, low humidity, no wind. At temperatures between 32 to 40 F, damage may be quite variable and strongly influenced by small variations in slope or terrain that affect air drainage and thermal radiation, creating small frost pockets. Field edges, low lying areas, and the top leaves on the plant are at greatest risk. Greener corn has more frost resistance than yellowing corn.
Symptoms of frost damage will start to show up about 1 to 2 days after a frost. Frost symptoms are water soaked leaves that eventually turn brown. Because it is difficult to distinguish living from dead tissue immediately after a frost event, the assessment should be delayed 5 to 7 days.
Grain quality impact Continue reading
October 2019 – Weather Prediction
Source: Jim Noel
After another hot week (until late this week), a cool down to normal temperatures is expected starting either Oct. 3 or 4 that will last through Oct. 15. Temperatures are expected to return to above normal (but no where near current levels) from Oct. 15-31.
Rainfall will be above normal in northern Ohio this week. The week of Oct. 7 will be normal or below normal but confidence is next week’s rainfall pattern is low to moderate. Above normal rainfall is in the outlook for the second half of October which could slow harvest after Oct. 15.
The hot and drier pattern for a good part of September was caused in part by tropical activity. The remnants of Dorian created a big low pressure system not far from Greenland while a typhoon called Lingling in the western Pacific created a big low pressure near Alaska. This resulted in a hot and dry dome of high pressure over the Southeast U.S. and wet weather in the western corn and soybean belt.
This pattern appears ready to breakdown later this week.
We are moving into frost and freeze season and overall it still looks like a delayed frost and freeze season. Most see their first freeze by Oct. 10-20. Currently, it still looks like a normal to later than normal first freeze.
The November outlook still indicates a warmer than normal month with precipitation not far from normal (but with a lot of uncertainty). We will keep you posted on this.
Finally, the two week rainfall outlook from OHRFC can be found here:
https://www.weather.gov/images/ohrfc/dynamic/NAEFS16.apcp.mean.total.png .
It shows the wettest areas being the western two-thirds of the corn and soybean belt. Rainfall for the next two weeks in Ohio will be 1-2+ inches in northern Ohio but generally 0.10-0.50 inches in southern Ohio. Normal is about 1.5 inches for two weeks.
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.
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.
It’s that time of year … Don’t forget to calibrate your yield monitor!
Remember the old adage … Garbage in = Garbage out. Many of us use our yield data to make additional management decisions on our farms such as hybrid or variety selection, fertilizer applications, marketing, etc. Data from an uncalibrated yield monitor can haunt us for many years by leading us into improper decisions with lasting financial affects. In today’s Ag economy we can ill afford any decision with adverse financial implications.
The two biggest reasons I usually hear for not calibrating a yield monitor are 1) I just don’t have time to do it or 2) I can’t remember how to do it without getting my manual out. While I know it’s easy to criticize from “the cheap seats”, I would argue that this could be some of the most important time you spend in your farming operation each year. Like many other tasks on our farm, the more we do it, the easier it gets. Yield monitor data has so much value! This data provides a summary (in term of yield) of every single decision you made on your farm during the past year.
Below is a calibration checklist created by Dr. John Fulton and Dr. Elizabeth Hawkins.