CORN
Crop Observation and Recommendation Network

October 6 - 12, 2003
C.O.R.N. 2003-34

In This Issue:

A) Grain Quality Issues From Drydown to Re-wetting
B) Frosted Soybeans
C) Assessing the Impact of the "Early" Frost on Corn
D) Management to Reduce Risk of Prussic Acid Poisoning

A) Grain Quality Issues From Drydown to Re-wetting - Beuerlein CORN Questions

The grain of any crop should be harvested as soon as possible following maturity when the suitable harvest moisture is reached. Every time soybean grain gets wet, it thinks it has been planted and starts the germination process which converts oil, protein and carbohydrates to compounds needed for growth. This is a dry matter loss which reduces the weight of a seed but not its size, and results in reduced test weight. This dry weight loss is also pounds of grain that we don't get paid for. Continued wetting and drying also lowers other quality factors and the overall value of the grain. Our recommendation is that soybean harvest should start as soon as the grain moisture gets below 20 percent. Grain quality (test wt. and other factors) for soybean is maximum when soybeans are harvested at 17 - 20 percent moisture and on the first dry-down. The re-wetting of mature corn and wheat grain has the same effect on grain quality as for soybeans.

B) Frosted Soybeans - Beuerlein CORN Questions

The recommendation for late June-planted and double crop soybeans is to use the latest maturity variety that will mature before frost. That did not work in 2003 because the first frost came one to two weeks earlier than normal and because late planted beans were exposed to cooler temperatures, wetter conditions, and more cloudy weather than normal causing the crop to progress more slowly than normal. The early frost killed much of the late-planted crop in mid pod-fill. The yield, harvestability, grain quality, and marketability of frost-killed soybeans is a function of the date of planting and the relative maturity rating of the variety. Fields that were near physiological maturity when frosted will dry slowly, but will be harvestable and the grain marketable although the seeds will be small. Fields not as far along will have more problems: very small seeds, some green seeds, dry down very slowly, and produce poor yields. Some of the seeds with green color at harvest will turn yellow during storage if they were close to physiological maturity when frosted. Blending of good and poorer quality grain may be a way to market poor quality grain. It may not be feasible to harvest some fields due to low yield and/or poor grain quality. Each field must be judged on a field-by-field basis. In some cases we may need to harvest a half acre just to see what we are dealing with in terms of quality and yield. If an unharvestable field had a 10 bu/ac yield, then the nitrogen credit for next year would be 60-75 pounds if the residue is incorporated prior to planting the next crop.

C) Assessing the Impact of the "Early" Frost on Corn - Thomison CORN Questions

Hard freezes occurred across Ohio last Thursday and Friday (Oct. 2 and 3). Many growers are concerned about crop damage from the early frost, especially since a number of fields were planted late and/or developing slower than normal due to the relatively cool growing season. According to the Ohio Agricultural Statistics Service as of Oct. 5, 2003, only sixty-two percent of the Ohio corn crop was mature (compared to 68 percent last year and 79 percent for the five-year average). What impact will this early frost have on corn that had not yet reached maturity?

The following information is adapted from "Handling Corn Damaged by Autumn Frost" (National Corn Handbook Chapter 57 available on-line at http://www.agcom.purdue.edu/AgCom/Pubs/NCH/NCH-57.html [URL verified 10/2/03].) .

The influence of frost damage on final grain yield depends on how much leaf tissue is killed and the stage of development when the frost occurs. Severe frost will not affect grain yield or quality after physiological maturity (when kernel black layer appears), and drying rate is influenced by hybrid and environment. Kernel moistures will be less than 40%, and harvest can occur following the normal fall drying period. The effect of frost on grain yield becomes smaller the closer the plant is to physiological maturity. A hard frost at the soft dough stage may result in yield of losses of 34 to 36% whereas if it occurs at the late dent stage, it may result in yield losses of only 4 to 8%. Redistribution of sugars from stalks to ears, despite complete leaf death, will increase kernel dry weight beyond that present on the frost date and reduce yield loss, unless the freeze is severe enough to kill stalks, husks, and kernels. If any leaves, especially above the ear, or even the stalk, ear shank, and husk are still green after a frost, grain dry weight will increase until the black layer forms at kernel tips. However, several days of cool temperatures (daily highs of 45 to 55F) during grain fill may result in premature black layer formation, ending further grain yield increases even if another frost has not occurred.

Corn that is frost-killed during the early- to mid-dent stage will contain more than 50% kernel moisture and can be harvested for grain or ear-corn after a long field-drying period. Grain yields will be reduced and test weights will be below normal. If only a portion of the plant tissue is killed and/or if the grain was in the late dent stage before the frost, yield loss will be small and test weights will be close to normal.

Source:
Carter, P.R. and O.B. Hesterman. 1990. Handling Corn Damaged by Autumn Frost (NCH-57). Purdue Univ. Extension Service.
Available online at http://www.agcom.purdue.edu/AgCom/Pubs/NCH/NCH-57.html [URL verified 10/2/03].

D) Management to Reduce Risk of Prussic Acid Poisoning - Mark Sulc CORN Questions

Jack Frost has taken his first bites of the year and with it comes the potential of prussic acid toxicity associated with feeding animals forage from the sorghum family. Those forages contain cyanogenic glucosides, which are converted quickly to prussic acid in frozen plant tissue. Prussic acid is also known as hydrogen cyanide (HCN), and if present in the frosted forage can kill animals within minutes of feeding.

Sudangrass varieties are low to intermediate in prussic acid poisoning potential, sudangrass hybrids are intermediate, and sorghum-sudangrass hybrids and forage sorghums are intermediate to high. Johnsongrass, chokecherry, and black cherry also have potential for prussic acid poisoning. Piper sudangrass has low prussic acid poisoning potential, and pearl millet and foxtail millet are virtually risk-free.

Other common forages such as alfalfa, clovers, and cool-season perennial grasses do NOT produce toxic compounds after a frost and can be fed safely. The only concern is a slightly higher potential for bloat when grazing legumes within a day or two after a killing frost.

Prussic acid (hydrogen cyanide) is a gas so feeding management for the sorghum forages after a frost involves allowing enough time for the gas to dissipate from inside plants. Fresh forage is generally higher in prussic acid than in silage or hay because HCN is volatile and dissipates as the forage dries. The following provides more specific guidelines:

Hay. Prussic acid content decreases dramatically during the drying process and the forage should be safe once baled as dry hay. The forage can be mowed anytime after a frost. It is very rare for dry hay to contain toxic levels of prussic acid. If the hay was not properly cured, it should be tested for prussic acid content before feeding.

Wilted Silage or Balage. Forage that has undergone silage fermentation is generally safe to feed. To be extra cautious, wait 5 to 7 days before chopping after the forage was frosted. If the plants appear to be drying down quickly after a killing frost, it can safely be ensiled within a shorter time period from the frost. Delay feeding silage for 8 weeks after ensiling. If the forage likely contained high HCN levels at time of chopping, hazardous levels of prussic acid might remain and the silage should be analyzed before feeding.

Grazing or Greenchop. Green chop forage is generally safer than the same forage pastured, but both methods have higher risk potential than silage or hay. The following guidelines reduce the risk of prussic acid poisoning when green chopping and grazing:

1. Graze or green chop only after the forage is greater then 18 inches tall. Young , rapidly growing plants are likely to contain high levels of HCN.
2. Do not graze or green chop wilted plants or plants with young tillers.
3. Do not graze on nights when frost is likely. High levels of the toxic compounds are produced within hours after a frost occurs.
4. Do not graze or green chop after a killing frost until the plants are dry. Wait 5 to 7 days to allow the released cyanide to dissipate.
5. Do not graze or green chop for two weeks after a non-killing frost or after a series of light frosts.
6. Don't allow hungry or stressed animals to graze young sorghum grass growth. Ruminants are particularly susceptible because cud chewing and rumen bacteria contribute to releasing the cyanide.
7. Plants growing under high nitrogen levels or in soils deficient in soil phosphorous or potassium tend to have high levels of cyanogenic glucosides, the precursors to prussic acid. Split applications of nitrogen decrease the risk of prussic acid toxicity, and proper levels of phosphorous and potassium in the soil will also help reduce the risk.

Additional Information. For more details on prussic acid poisoning potential of forages, two articles are available through the Ohio Dairy Industry website. Go to http://dairy.osu.edu, and click on Business Resources Feed Feeding Management and look under "Forages". The direct URL's are:
http://www.agnr.umd.edu/MCE/Publications/Publication.cfm?ID=8%20, and http://dairy.osu.edu/resource/feed/Feeding%20Frosted%20Forages.pdf

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

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