C.O.R.N. Newsletter 2004-34

Frost and Sudan-type Grasses

Authors: Bill Weiss

Some summer annual grasses contain compounds that can be converted to cyanide when the plant cells are damaged. The concentrations of these compounds vary among plant species: sorghum contains the highest concentrations, followed by sorghum-sudangrass crosses (sudax), and sudangrass contains the lowest concentrations. The concentrations of these compounds are highest in immature plants and decrease as the plant matures and leaves contain much higher concentrations than do stems. Frost will damage or kill plant cells which allows the formation of cyanide making the forage toxic to ruminants. Ruminants should not be allowed to graze frost-damaged sorghum, sudax and sudangrass. The cyanide that is produced following a frost will eventually dissipate into the air after the killed plant material wilts. This usually requires 5 or 6 days after a frost. If the frost completely kills the plant, grazing can resume 5 or 6 days later, however, if the plants were not completely killed, grazing after a frost has a high risk of causing toxicity because regrowth usually contains high concentrations of toxic compounds. Therefore, grazing of these types of plants should cease once the first frost has occurred and should not commence again until 5 or 6 days following a killing frost.

Frost-damaged sorghum, sudax, and sudangrasses can be made into hay or silage with little or no risk of toxicity. When the plants are wilted enough to make hay, most of the cyanide, which is volatile, will have dissipated. Normal silage making also allows most of the cyanide to dissipate, but the silage should not be fed for at least 3 wk following ensiling. Feeding green-chopped forage that has been frost damaged has a lower risk than grazing because of reduced selection by the animals, however, green-chopped sorghum, sudax, and sudangrass can still be toxic.

Yields are Surprisingly High for Early Planted Beans

Authors: Anne Dorrance

The early reports are in from last week and by all accounts yields are good, including some of my research plots. I can’t believe these yields. This truly is a mighty bean! As many of you have watched your yield monitors over the past few weeks, you probably saw it bouncing or taking dips in certain areas of those fields. Or there is that one field that was 5 to 15 bushels less than all of the others. Those are the fields to plan for sampling for Soybean Cyst Nematode (SCN). SCN is increasing across the state and it is mainly just sucking the yield out of the plants in many of these fields. Soybean Cyst Nematode is a roundworm, that invades roots and in the adult stage the females stay in one spot and begin to swell with eggs. These females look like white pearls along the roots and for those fields that you haven’t harvested, you can still find them on the roots if SCN populations are high.

There are other symptoms of SCN in fields besides lower yields. Areas of the field that are early maturing, or soybean plants are stunted compared to the rest of the field, and the presence of sudden death syndrome all indicate a problem. If this is happening then sample your fields to determine the levels of SCN in the field. If SCN levels are high – then Crop rotation is the way to go. IF SCN levels are moderate to low and you are insisting on growing beans in that field, then a SCN resistant variety may be the way to go. IF you are growing continuous beans AND they are SCN resistant lines, you need to begin to sample every year to monitor if the resistance is still effective. SCN resistance is evaluated by the number of females that reproduce on the line compared to the susceptible check.

Precautions When Saving Soybeans for Seed

Authors: Jim Beuerlein

Home-grown grains are often low in quality and germination and are frequently contaminated with weed seed and should not be used for seed except in an emergency, and then only after it has been cleaned, tested for germination and vigor, and treated with the appropriate fungicides. If home-grown grain is to be used for seed, then the seed field should be carefully harvested with a machine adjusted to maintain the best grain quality. The grain should be harvested when the grain moisture is four to eight percentage points higher than the proper storage moisture to reduce damage to the grain and then handled gently to avoid damaging the seed coat. Seeds with any amount of physical damage almost never produce a productive plant. Cracked seed, seeds with part or all of the seed coat missing or with a scratched seed coat, seed halves, seed parts and seeds with chips missing will not survive the cleaning and treating process and then produce a plant in the field. The cost of professionally produced and conditioned seed is only slightly more expensive than that of saved grain that has been properly cleaned, conditioned, and treated with the appropriate fungicides and insecticides and is an excellent value. Investment in new seed each planting season encourages seed companies to develop new, better-adapted, higher-yielding varieties that generate more income than can be realized from using one’s own grain for seed.

All carryover seed and all grain saved for seed should be tested for germination and vigor before use. For grains saved on the farm, these tests should be conducted before the grain is cleaned, treated with a fungicide, and bagged. Two laboratories in Ohio specialize in testing all kinds of seed for germination, purity, vigor, and other quality traits. These laboratories are:

Central Ohio Seed Testing
P.O. Box 1580
6150 Avery Road
Dublin, OH 43017-6580
Phone: (614) 792-0334
Fax: (614) 889-8979

Seed Technology, Inc.
P.O. Box 397
1383 Columbus Avenue
Marysville, OH 43040
Phone: (513) 644-0088
Fax: (513) 644-0602

Seed Quality Test:

Standard Germination - This warm germination test is conducted for 5 to 8 days at a temperature of 77 º F and represents such ideal conditions for germination that even weak seed will often germinate. This is the germination percentage reported in the seed labeling information required for all seed offered for sale. This test can be conducted on either fungicide treated or untreated seed.

Cold Test - this test is designed to measure the ability of seeds to germinate under high soil moisture and low soil temperature conditions. This vigor test simulates early season adverse field conditions and usually represents the lowest germination rate that would be expected from seed planted in such conditions. Actual field germination will normally fall between the cold test and the warm test results. This test can be conducted on either fungicide treated or untreated seed. A germination percentage of 70 or greater is considered to be very good.

Accelerated Aging - this vigor test estimates the carryover potential of seed in warehouse storage. The seeds are exposed to high temperatures and high humidity for short periods of time. Seeds are suspended over water in a special chamber for 72 to 96 hours depending on the species and then removed and evaluated using the standard warm germination test. This test is recommended for frost injured seed corn, carryover corn and soybean seed, and pre-sprouted wheat seed. This test can be conducted on either fungicide treated or untreated seed.

Tetrazolium (TZ) - this test is known as a “quick test” for seed viability and can be very useful when the approximate germination rate is needed quickly. This test will not indicate disease as a warm germination test does but is highly reliable for corn, soybeans, wheat and other grasses.

Time To Spray “Cool-Season” Weeds in Wheat Stubble Fields

Authors: Mark Loux

Based upon the current forecast of frost this week, “cool-season” perennial and biennial weeds are beginning to send photosynthates to plant parts below ground in order to grow next season. As the photosynthates head downward, translocating herbicides - especially glyphosate, will be taken to those underground growing points and kill these plants. “Cool-season” perennial and biennial weeds include quackgrass, Canada thistle, dandelion, curly dock, wild carrot, poison hemlock, and others that tolerate frost.

For control of perennial species, plants should be at least 8 to 12 inches tall and should not be under moisture stress. Apply herbicides during warm and sunny conditions for most effective control. Apply at least 0.75 pound acid equivalent per acre of glyphosate (Roundup WeatherMax at 22.0 ounces/A, Touchdown Total at 24.0 ounces/A, or any 3.0 pound acid equivalent/gallon glyphosate formulation at 32.0 ounces/A). If perennial grass species and Canada thistle are present in the field, do not add 2,4-D due to antagonism between 2,4-D and glyphosate. The addition of 2,4-D ester to glyphosate should improve control of all other broadleaf species.

Soil Sampling This Fall

Authors: Robert Mullen

As crops come out of the field, thoughts should turn to soil testing to determine what needs to be applied for next spring’s crop. So in preparation for an increased number of soil probes being taken to the field, here are some things to remember:

• Collect 15 to 20 random samples from representative areas of the field. Representative areas are those areas that best representative soil conditions across the field landscape. Areas at different landscape positions or “problem” areas should be sampled separately. Make a composite sample of the 15 to 20 samples and make certain that is well mixed. Take a small sample of the composite and submit it to a reputable lab. Labs available in Ohio can be found at the following webpage: http://www.ag.ohio-state.edu:8000/%7Ecorn/library/testlabs.pdf
  Ohio State University does not operate a soil testing lab.


• Collect soil samples to a depth of 8 inches. Tri-State Fertilizer Recommendations are based on soil samples collected to a depth of 8 inches. If sampling no-till fields, 4 inch samples should also be collected. This is for determination of lime recommendations.


• Do not dry soil samples at temperatures higher than 120 degrees F. Typically semi-moist samples can be submitted directly to analytical labs.


• Avoid contamination. Use clean probes for sampling and clean buckets for mixing.

As noted in previous CORN newsletters, fertilizer prices appear as if they are going to be higher this year. Using soil testing to determine fertility levels can lead to significant fertilizer savings. Remember: Don’t guess – soil test!

Managing Flooded Fields

Authors: Robert Mullen

Recent flooding in the Eastern and Southeastern portions of the state may create some challenges for next year’s crop. From a fertility standpoint, deposition of sand on production fields may cause some nutrient deficiencies to appear, specifically phosphorus and micronutrients. The sand deposited is likely very low in organic matter which contributes to micronutrient deficiencies. Soil testing is an excellent way to determine the nutrient level of the soil. If the problem is sporadic across the field, do not mix soil samples from affected areas with “normal” areas.

Depending upon the depth of the deposited material, tillage may be considered for reclamation. Kansas State University has several good articles that can help you make your decision. Articles can be found at the following web addresses.

Soil Nutrient Management After the Flood –
http://www.oznet.ksu.edu/library/crpsl2/mf1147.pdf

Reclaiming Flooded Land with Tillage -
http://www.oznet.ksu.edu/library/ageng2/mf1149.pdf

Managing Soil Compaction on Flooded Fields -
http://www.oznet.ksu.edu/library/ageng2/mf1150.pdf

Other articles from Kansas State can be found at:
http://www.oznet.ksu.edu/library/Flood/

Frosted Soybeans

Authors: Jim Beuerlein

The effect of a heavy frost on non-mature soybeans varies depending on the stage of growth when the frost occurs. Plants with yellowing leaves will not be adversely affected because all the grain on those plants has reached physiological maturity. Plants with green leaves may have grain that is near physiological maturity and also very immature grains that cannot be saved. Some of this harvested grain will have a green color that will turn yellow in storage, while more immature grains with green color will retain the green color in storage. Plants with both mature and immature grain will suffer a yield loss in proportion to the percent of grain that is immature. Grains that were about 80 percent of full size will probably dry down at the normal rate and be harvestable. Less mature grain may not dry and probably will not thrash free of the pod if it does dry. Grain less than half full size will likely be lost.

Unharvested crops with mostly immature grain have a significant value as nitrogen for corn next year. Stems and leaves will have about 5 percent nitrogen on a dry weight basis. A 30-inch tall crop should have 2000 to 4000 pounds of dry matter in the form of stems and leaves and contain 100 to 200 pounds of nitrogen. Each bushel of immature grain would contain an additional 3 pounds of nitrogen. The vegetation must be incorporated into the soil to be recovered by a crop next year. Almost all this nitrogen is in an organic form and not subject to leaching or denitrification until converted to nitrate. Normally, 50% to 80% will be recovered next year and the balance the following year. Also, little if any of it will be released at soil temperatures below 55 degrees F. and little will be released when the soil is dry.

Immature crops may also be made into silage and should produce yields of one to two tons of dry matter per acre. Soybean plants made into silage at the early pod stage have 16% dry matter, 16% crude protein, 40% acid detergent fiber, and 49% neutral detergent fiber.