http://www.ag.ohio-state.edu/~corn/

CORN
Crop Observation and Recommendation Network

August 9-15, 1999
C.O.R.N. 99-21

In This Issue:

A) Identifying Sudden Death Syndrome In Soybeans
B) Estimating Yield Losses In Drought Damaged Corn Fields
C) Whole Soybean Plants For Cattle
D) Determining Moisture Content Of Whole Plant Corn
E) Dry Weather May Hamper Summer Forage Seedings

A) Identifying Sudden Death Syndrome In Soybeans – Anne Dorrance CORN Questions

Sudden death syndrome of soybean has been identified in a few fields in Ohio this past week. Sudden death syndrome is a fungal disease of soybeans that attacks the root system. The fungus, Fusarium solani fsp glycines, lives in the soil and is often associated with soybean cyst nematode.

Disease severity is greatest when there are high levels of moisture before and during the flowering period. The fungus colonizes the crown and is believed to produce compounds that are phytotoxic to the plant. This results in foliar symptoms which are very similar to brown stem rot.

The foliar symptoms start out as chlorotic spots, which turn brown, but the veins remain green. In brown stem rot the leaves will wither and stay on the plants, in sudden death they will fall off leaving the petioles. Another characteristic to differentiate the two diseases is to examine the stem pith. In sudden death the crowns of the plant will be gray and the pith will be white. In brown stem rot, the pith will be a chocolate brown. Fact Sheet AC-44-98 details SDS in Ohio and can also be found at http://ohioline.ag.ohio-state.edu/ac-fact/0044.html. Images of SDS can be found at http://www.ipm.iastate.edu/imagegal/plantpath/soybean/sds and http://plantpath.wisc.edu/~soyhome.

Disease management strategies for sudden death syndrome include the use of resistant varieties, manage cyst nematode populations, late planting to escape infections and increase drainage in those fields where sudden death is a problem.

B) Estimating Yield Losses In Drought Damaged Corn Fields – Peter Thomison CORN Questions

Corn growers with drought damaged fields may want to predict grain yields prior to harvest in order to help develop grain marketing plans. Two procedures which are widely used for estimating corn grain yields prior to harvest are the YIELD COMPONENT METHOD (also referred to as the "slide rule" or corn yield calculator) and the EAR WEIGHT METHOD. The YIELD COMPONENT METHOD can be used to give yield estimates 4 to 6 weeks ahead of harvest. Each method will often produce yield estimates that are within 20 bu/ac of actual yield.

THE YIELD COMPONENT METHOD can be used as early as the milk stage of kernel development. The yield component method uses a numerical constant for kernel weight in an equation to calculate grain yield. Since weight per kernel will vary depending on hybrid and environment, the yield component method should be used only to estimate relative grain yields, i.e. "ballpark" grain yields.

When below normal rainfall occurs during grain fill (resulting in low kernel weights), the yield component method will OVERESTIMATE yields. In a year with good grain fill conditions (resulting in high kernel weights) the method will underestimate grain yields.

Step 1. Count the number of harvestable ears in a length of row equivalent to 1/1000th acre.
For 30-inch rows, this would be 17 ft. 5 in.

Step 2. On every fifth ear, count the number of kernel rows per ear and determine the average.

Step 3. On each of these ears count the number of kernels per row and determine the average.
(Do not count kernels on either the butt or tip of the ear that are less than half the size of normal size kernels.)

Step 4. Yield (bushels per acre) equals (ear #) x (avg. row #) x (avg. kernel #) divided by 90.

Step 5. Repeat the procedure for at least four additional sites across the field.

Example: You are evaluating a field with 30-inch rows. You counted 24 ears (per 17' 5" = row section). Sampling every fifth ear resulted in an average row number of 16 and an average number of kernels per row of 30. The estimated yield for that site in the field would be (24 x 16 x 30)divided by 90, which equals 128 bu/acre.

THE EAR WEIGHT METHOD can only be used after the grain is physiologically mature (black layer), which occurs at about 30-35% grain moisture. Since this method is based on actual ear weight, it should be more accurate than the yield component method above. However, there still is a ‘fudge factor’ in the formula to account for average shellout percentage.

Sample several sites in the field. At each site, measure off a length of row equal to 1/1000th acre. Count the number of harvestable ears in the 1/1000th acre. Weigh every fifth ear and calculate the average ear weight (pounds) for the site. Hand shell the same ears, mix the grain well, and determine an average percent grain moisture with a portable moisture tester.

Calculate estimated grain yield as follows:

Step A) Multiply ear number by average ear weight.

Step B) Multiply average grain moisture by 1.411.

Step C) Add 46.2 to the result from step B.

Step D) Divide the result from step A by the result from step C.

Step E) Multiply the result from step D by 1,000.

Example: You are evaluating a field with 30-inch rows. You counted 24 ears (per 17 ft. 5 in. section). Sampling every fifth ear resulted in an average ear weight of 1/2 pound. The average grain moisture was 30 percent. Estimated yield would be [(24 x 0.5) / ((1.411 x 30) + 46.2)] x 1,000, which equals 135 bu/acre.

Since drought stress conditions this year have resulted in poorly filled small ears, there may be mechanical difficulties with sheller or picker efficiency which need to be considered. Since it will probably be cheaper to buy corn for grain than to buy hay for roughage (because of the likely forage deficit), there will be greater benefit in harvesting fields with marginal corn grain yield potential for silage.

Link to this and other timely drought related articles at http://www.ag.ohio-state.edu/~corn/drought99/index.html

C) Whole Soybean Plants For Cattle – Bill Wiess  CORN Questions

Because of drought conditions, soybeans in some areas of the state will not be harvested for seeds. Whole plant soybeans can be excellent forage for cattle. Under normal growing conditions, soybean with little pod development can have about 18% crude protein and 40 to 45% neutral detergent fiber. In other words, whole soybean plants are similar to good quality alfalfa in nutritional value. Soybeans can make good silage if two conditions are met.

  1. If seeds are well-developed do not chop for silage (too much oil). If seeds did not develop or are small, silage is an option if dry matter content is ok.
  2. Prior to chopping beans for silage, check dry matter content.

(Article D in this newsletter addresses a method to determine moisture content). If the plant contains less than 45% dry matter (at least 55% moisture), the plants should ferment fine in upright and bag silos and will usually ferment ok in bunker silos. If the plant contains more than 50% dry matter (less than 50% moisture, fermentation quality will probably be poor in bunker silos. When dry matter is much higher than 55% fermentation will be poor in all types of silos except sealed structures.

If plants do not contain enough moisture for fermentation, water can be added but it takes a lot of water to change the dry matter content. To increase the moisture content of 1 ton of material by 4 percentage units (for example 55 to 51% dry matter), you have to add about 190 lbs. of water (24 gallons per ton).

Whole plant soybeans can be harvested for hay but generally the nutritional value is much lower than soybean silage. Leaf shatter is severe when soybeans are baled so protein is much lower and fiber much higher in soybean hay. One precaution regarding whole plant soybeans for livestock feed is herbicide use. Check the label to see if the herbicide is cleared for this use.

Link to this and other timely drought related articles at http://www.ag.ohio-state.edu/~corn/drought99/index.html

D) Determining Moisture Content Of Whole Plant Corn – Mark Sulc and Maurice Eastridge CORN Questions

The proper time to harvest corn for silage is an important decision. Whole plant dry matter (DM) content varies with maturity and affects fermentation. Ensiling corn that is too wet produces poor fermentation, seepage losses, and lowered animal intake. Ensiling corn that is too dry increases the risk of heat damage and molding. Below is the optimal DM content for ensiling corn in different structures:

It is very difficult to visually judge the DM content of whole plant corn, especially under stress conditions. The kernel milkline has been used to estimate the proper time to harvest corn silage. In our region, when the kernel milkline is in the UPPER 1/4 of the kernel, the crop is often very near the optimal time to harvest. BUT UNDER STRESS CONDITIONS, THE KERNEL MILKLINE METHOD CAN BE VERY MISLEADING. In addition this method cannot be used when the corn is so stressed that ear development is not normal or non-existent. Below are several alternatives for determining the moisture content of corn before ensiling.

The easiest alternative is to check with your feed service representative, because many offer the service of determining corn silage moisture. If this service is not available, then use the steps described below.

  1. Collect a representative sample from the field and seal in a plastic bag. The most accurate method is to chop a partial load and collect a subsample. If you can feed the greenchop, this is a good option (Be aware of the potential for high concentrations of nitrates). Otherwise, collect two representative plants from the field and chop into pieces. Use the entire 2 plants in the sample. Better accuracy will be achieved if several 2-plant samples are collected from different parts of the field. Testing several samples is a good option especially for those having their own commercial moisture tester.
  2. Follow the directions given with the commercial moisture tester for determining DM percentage. A microwave can be used if you have chopped a partial load and collected a subsample, otherwise the sample will be too bulky to be used in a microwave. Directions for using a microwave can be found on Ohioline at http://www.ag.ohio-state.edu/~ohioline/agf-fact/agf-0004.html or request a copy of AGF-004 from any county extension office.
  3. If you do not have access to a moisture tester, send the sample to a lab. Most labs can give next day service (once they receive the sample) if you request a call back with the results. To minimize cost and to obtain additional nutritional information, the NIR method can be requested for measuring DM, NDF, and CP.

You should encounter no problems with fermentation of corn that is low in grain content, provided that it is ensiled at the proper DM content as shown in the table above.

E) Dry Weather May Hamper Summer Forage Seedings  – Mark Sulc CORN Questions

Late summer can be an excellent time to establish forage crops. The most critical factor to successful summer seeding is having adequate moisture. Drought-stricken parts of Ohio currently lack the soil moisture necessary to ensure good stand establishment this year. Unless significant rainfall occurs soon in those areas, producers should not risk summer seeding. It is very risky to place seeds into bone-dry soil and hope for rains to come. Some areas of the state have received rainfall recently, and in those areas where soil moisture is present, seeding now in August is an excellent alternative.

The following 10 steps will improve the chances for successful stand establishment:

  1. Soil test and apply needed lime and fertilizer and control problem perennial weeds ahead of seeding. A preplant incorporated herbicide is usually not required when using tillage to prepare seedbeds. Post-emergence herbicides can be used later if winter annual weed problems develop later.
  2. Prepare a very firm seedbed if using tillage. A loose seedbed dries out quickly. A cultipacker or cultimulcher is an excellent last-pass tillage tool. The soil should be firm enough for a footprint to sink no deeper than 3/8 to 0.5 inch. Plant seed shallow and in firm contact with the soil. Drills with press wheels will be most successful in the summer. Surface broadcasting seed without good soil contact and firm packing is usually a recipe for failure.
  3. No-till seeding is an excellent way to conserve moisture, provided weeds are controlled prior to seeding. Remove all straw after small grains. Any remaining stubble should either be left standing, or clipped and removed. Do not leave clipped stubble on the field as it will form a dense mat that will prevent good emergence.
    CAUTION: No-till or reduced-till summer seedings of legumes are at risk of infection by Sclertotinia crown and stem rot, especially in fields where clover or alfalfa were recently grown. Planting from mid- to late-August will dramatically increase the risk of damage by this disease compared with planting earlier, so plant legumes as early as possible.
  4. Seed when soil moisture is adequate for germination and early seedling growth, or a strong rain system is in the forecast. Do not seed into a very dry seedbed, as there may be just enough moisture to germinate the seed but not enough for seedling establishment.
  5. Do not use a companion small grain crop, as it will compete for moisture.
  6. Seed early. Seedlings require 6 to 8 weeks of growth after emergence to have adequate vigor to survive the winter. Seed by August 15-20 in northern Ohio and by September 1 in southern Ohio. Slow establishing species like birdsfoot trefoil or reed canarygrass should be planted in early August or late July. Fast establishing species like red clover, alfalfa, and orchardgrass can be seeded up to the dates listed above if moisture is present. Kentucky bluegrass and timothy can actually be seeded 10 to 15 days later than the dates listed above.
  7. Scout new summer seedings for insects. Watch carefully for leafhopper damage on legumes soon after emergence.
  8. Do not harvest new summer seedings this fall.
  9. Scout new seedings for winter annual weeds in October to November, and apply herbicides as needed. Winter annual weeds are much easier to control in the fall than next spring.
  10. Summer-seeded fields should be the last fields harvested next spring. This will allow plants to become well established and build carbohydrate reserves for strong regrowth.

Link to this and other timely drought related articles at http://www.ag.ohio-state.edu/~corn/drought99/index.html

Readers can subscribe electronically to this newsletter by sending an e-mail message to: corn-out-on@postoffice.ag.ohio-state.edu. A successful subscription message will receive by an automatic reply from the listserv. Contact your local Ohio State University Extension Office or e-mail labarge.1@osu.edu if you have problems subscribing.

Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/

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.

Contributors to C.O.R.N. this week include: State Specialists: Anne Dorrance (Plant Pathology), Ron Hammond & Bruce Eisley (Entomology), Peter Thomison (Corn Production) Maurice Eastridge (Animal Science), Bill Weiss (Animal Science) and Mark Sulc (Forages); Woody Joslin (Shelby), Glen Arnold (Putnam), Dennis Baker (Darke), Clark Hutson (Seneca) and Greg La Barge (Fulton).

Editor: Greg LaBarge         Web Editor: Steve Lichtensteiger

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868

| Drought'99 | C.O.R.N. | Newsletter | Archive | Search | Questions? | Ohioline | Publications |