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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2004-23

Dates Covered: 
July 20, 2004 - July 26, 2004
Steve Prochaska

Late Summer Seeding of Forage Crops

Authors: Mark Sulc

Late summer can be an excellent time to establish forage crops, provided there is sufficient moisture for germination and good seedling growth. It is also a good time to seed in bare or thin spots in forage stands established this spring. The following steps will improve the chances for successful forage stand establishment in late summer.

1. Apply lime and fertilizer according to soil test and control problem perennial weeds ahead of seeding. Be careful with herbicide selection because some have residual soil activity and will harm new forage seedings in proper waiting periods are not observed. Read the labels for details.

2. Prepare a firm seedbed if using tillage. Loose seedbeds dry out very quickly. Deep tillage should be completed several weeks ahead of seeding so rains can settle the soil before final seedbed preparation. 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.

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 in fields as it forms a dense mat that prevents good emergence. CAUTION: No-till or reduced-till summer seedings of legumes are at risk of infection by Sclerotinia crown and stem rot, especially in fields where clover or alfalfa were present recently. Mid- to late-August plantings dramatically increase the risk of damage by this disease compared with planting earlier.

4. Don’t plant alfalfa immediately after older established alfalfa. Autotoxic compounds are released by old alfalfa plants that inhibit growth and productivity of new alfalfa seedlings. It is best to rotate to another crop for a year before going back to alfalfa; however, thickening up Spring 2004 seedings is fine because autotoxicity is only an issue with older alfalfa.

5. Seed when soil moisture is adequate or a good rain system is in the forecast. It is very risky to place seeds into dry soil, as there may be just enough moisture to germinate the seed but not enough for seedling establishment.

6. Seed as early as possible. 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. 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 15 days or more later than the dates listed above. Keep in mind that the above dates assume sufficient moisture to establish the crop. Planting later than the dates mentioned above is sometimes successful depending on fall and winter weather patterns, but there is increased risk of failure and reduced yield potential for the stand as planting is delayed. A good rule of thumb for alfalfa is to have 6-8” of growth before a killing frost.

7. Plant seed shallow and in firm contact with the soil. Carefully check seeding depth, especially when no-tilling. Drills with press wheels usually provide the greatest success in the summer. Broadcasting seed on the surface without good soil coverage and without firm packing is usually a recipe for failure in the summer.

8. Use high quality seed of known varieties. Cheap seed often results in big disappointments and shorter stand life. Make sure legume seed has fresh inoculum of the proper rhizobium.

9. Do not harvest new summer seedings this fall. The only exception to this rule is perennial ryegrass. If perennial ryegrass has tillered and has more than six inches of growth in late fall, clip it back to 3 to 4 inches before snowfall.

10. 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 late fall than in the spring.

Identifying Nutrient Deficiencies

Authors: Robert Mullen, Edwin Lentz

Identifying nutrient deficiencies can go a long in a fertility program. Recognizing a nutrient deficiency within a certain area of a field can lead to more targeted soil sampling and targeted applications of nutrients in subsequent seasons. Here are some visual symptoms to look for when evaluating plants:

Nitrogen – N deficiency shows up as a yellowing (chlorosis) at the tips of lower leaves. It progresses down the leaf towards the stem along the midrib. If there is not adequate N uptake by the roots, lower leaves are aborted and their N is shipped up to the new growth because N is mobile in the plant. Although N deficiency is fairly easy to spot, crop appearance may lead to incorrectly diagnosing the soil as N deficient. N stress can be a factor of many things – true soil N deficiency, moisture stress, poor root development, or senescence of lower leaves (after tasseling). Thus identifying a soil as N deficient without a reference is difficult. To ascertain if the symptom is a true soil N deficiency apply a few “reference” (or N rich) strips in the field. The strips should receive an N rate slightly higher than the rest of the field. If clear differences can be seen between the reference strip and the rest of the field, then additional N is necessary. If there are no differences between the reference and the rest of the field, then additional N is not warranted (even if lowering leaves are firing). Tissue testing can also determine if an N deficiency exists, but the same pitfalls mentioned above occur with tissue testing.

Potassium – K deficiency can be confused with N stress because both symptoms begin with yellowing at the tips of the lower leaves. Lower leaves of K deficient plants have yellowing along the leaf margin toward the stem. Like N, K is mobile in the plants so lower leaves are affected first. Soil testing can readily reveal a K deficiency.

Phosphorus – P deficiency is characterized by a purpling of the leaf margin of lower leaves. Plants that are P deficient typically have a dark green color because leaf expansion is retarded more than chlorophyll and chloroplast formation. Soil testing can reveal if P is deficient.

Magnesium – Mg deficient plants are characterized by an interveinal yellowing of lower leaves. Mg is mobile in the plant so older leaves are the first to show visual symptoms. Mg deficiency is not common, but acid, sandy soils of Ohio can be deficient.

Sulfur – S deficiency appears as a general yellowing of higher leaves. Do not confuse S deficiency with N deficiency. Because S is not as easily translocated within the plant, younger leaves show the visual symptoms. S deficiency is not typically found in Ohio, but sandy soils low in organic matter are the most likely place for it to occur.

Iron – Fe deficient plants are characterized by an interveinal yellowing of higher leaves. Unlike Mg, Fe is not easily translocated within the plant so younger leaves are affected first. Fe deficiency is primarily limited to calcareous soils.

To view photos of nutrient deficiencies visit the following websites:
University of Minnesota Webpage , Iowa State University Webpage .


Nitrogen Deficiency, What is Going On?

Authors: Robert Mullen, Peter Thomison

Many of the corn fields across the state are reporting N deficiencies due to the appearance of yellowing (firing) lower leaves (see additional article to help identify what N stress looks like). With the wet spring, many are wondering how much of the N applied has survived denitrification/leaching (depending upon soil) and would additional N be beneficial.

The appearance of yellowing lower leaves indicating an N deficiency is probably the result of many factors. Considering the amount of rainfall that fell this spring, denitrification losses could be relatively high. The wet spring also contributed to poor root development of the crop. Soils have been drying out recently, and with the poorly developed roots, subsurface moisture is not being found (nor is N). So is the yellowing of the lower leaves directly tied to low N status of the soil? Maybe. It is likely a combination of the three things pointed out above. If N rates were a little conservative early in the year, N stress could be the result of low soil N due to denitrification/leaching. If N rates were high (>220 lbs/A), the likelihood of losing enough N this year to denitrification/leaching to cause N stress is slim. It is difficult to definitively state that the current plant stress is the result of soil N deficiency without a reference. Next season apply a couple of reference strips to determine if N management is supplying enough N. Reference (N “rich”) strips should be 25-35% higher than the normal rate and one applicator’s swath wide. This would allow for side-by-side comparison to determine if N is limiting.

So, as for this year, would late season applications of N result in a yield benefit? If the yellowing of lower leaves is due to soil N deficiency, then application may be beneficial (but if it’s due to limited root development, then it will probably be of limited benefit). Research reports that applications of N as late as silking can result in yield increases, but attaining maximum yield at this point with N application is unlikely (depends upon the level of stress). Consider the uptake of N as well, if urea is applied aerially and rain is inadequate resulting in poor incorporation, the response to the late N application may be limited.

Did Recent Dry Weather Impact Pollination?

Authors: Peter Thomison

Two methods are commonly used to assess the success or failure of pollination. One involves simply waiting until the developing ovules (kernels) appear as watery blisters (the "blister" stage of kernel development). This usually occurs about 10 to 14 days after fertilization of the ovules. However, there is a more rapid means by which to determine pollination success.

Each potential kernel on the ear has a silk attached to it. Once a pollen grain "lands" on an individual silk, it quickly germinates and produces a pollen tube that grows the length of the silk to fertilize the ovule in 12 to 28 hours. Within 1 to 3 days after a silk is pollinated, and if fertilization of the ovule is successful, the silk will detach from the developing kernel. Unfertilized ovules will still have attached silks. Silks turn brown and dry up after the fertilization process occurs. By carefully unwrapping the husk leaves from an ear and then gently shaking the ear, the silks from the fertilized ovules will readily drop off. Recent studies indicate that silks can remain receptive to pollen up to 5 to 6 days after emergence. The proportion of fertilized ovules (future kernels) on an ear can be deduced by the proportion of silks dropping off the ear. Sampling several ears at random throughout a field will provide an indication of the progress of pollination.

Scout Now For Corn Leaf Diseases

Authors: Patrick Lipps

The corn crop in Ohio is progressing, but there is tremendous variability in the growth stage of the crop from one location to another. In most of the more southerly counties pollination is already complete where in many northern counties that had significant rain through May and June many fields are not yet knee high or not yet tasseled.

Mid to late July is prime time to begin scouting for leaf diseases. Yield losses from leaf diseases are greatest when diseases occur on the ear leaf and the leaves above the ear before tasseling. Most disease management strategies are aimed at postponing the occurrence of diseases on the upper leaves until later in the season when yield losses are minimal. Corn producers do this by planting resistant hybrids, by reducing the survival of the disease causing fungi in the field through crop rotation and tilling to destroy residues of the previous crop. Occasionally, when weather conditions are highly favorable for disease development and a susceptible hybrid has been planted, fungicides are used to limit early development of disease by making an application before or soon after tasseling.

Growers should recognize and scout for three particularly important diseases that have been detected in fields already this season; northern leaf blight, common rust and gray leaf spot. We have had reports of each of these diseases and our previous experience indicates that yield losses can be quite great if they become severe early. In most instances where yield losses have been excessive, the hybrids planted were known to be susceptible to the disease. This is why we always recommend obtaining hybrids with the best resistance available.

Northern leaf blight can be recognized as large (2 to 6 inch long by 1 to 1.5 inch wide) spindle shaped lesions on leaves. The lesions on susceptible hybrids are tan and may have a dark colored border. The lesions increase in size as they age and spores can be seen as a dark olive green colored appearance to the center of the lesions. Northern leaf blight has caused significant yield losses in Ohio fields over the past 2 to 3 years and is a threat to the corn crop again this year. The disease is most severe under moderate temperatures (65 to 78 degrees F) and frequent rainfall with prolonged dew. Moisture on the leaf surfaces for 6 or more hours is required for infection to occur. Lesions develop within 7 to 12 days after infection. Spores produced in lesions are spread by rain splash or wind to adjacent leaves causing rapid spread in the field. Go to the following link to see an image of this disease .

Common rust is seen as very small, dark rust-red pustules scattered over the leaf surfaces. Spores are blown up from the south and arrive in Ohio by about mid June to early July. Spores germinate and infect the leaves in about 6 hours when water is present on leaf surfaces and the temperature is between 60 and 77 degrees F. Splashing rain, high humidity and moderate temperatures favor disease development. Go to the following link to see an image of this disease

Gray leaf spot lesions are rectangular in shape with straight or parallel sides caused by the inability of the fungus to grow through the major veins of the leaf. Lesions can be variously colored but typically are tan in the center and some may have an orange or yellow border. The rectangular shape of the lesions is highly characteristic. As the leaves age the lesions may merge resulting in significant leaf damage. Gray leaf spot development is favored by extended periods of high humidity resulting in heavy dew that keeps the leaves wet for 12 hours or more per day for several days. Lesion development may take two weeks or more depending on daily humidity in the field. The disease is more important in reduced tillage, continuous corn fields. Go to the following link view an image of this disease

Scouting fields now will help identify locations where these diseases are becoming important and will likely help explain lower yields in these fields later in the season. Excessive loss of leaf tissue now not only affects yield but the standability of the crop. Plants severely affected by leaf blight are frequently prone to stalk lodging problems at harvest.


Regional Crop and Livestock Conference Brings Technology To A New Level

Authors: Nathan Watermeier, Harold Watters

Equipping Today’s Agriculture with Technology will be the theme of the Info Ag Ohio Valley Conference, to be held August 16-17, 2004, on the campus of Clark State Community College in Springfield, Ohio.

This conference is focused on the needs and interests of farmers and their input suppliers and advisers in Ohio and the surrounding states. Environmental regulations, international competitiveness, homeland security, and many other factors challenge farmers and agribusinesses to manage more information and become more efficient and productive in order to maintain profitability.

Presentations and demonstrations will feature real-world experiences and successes in use of technology by crop and livestock producers to adjust to the demands of changing agriculture. Parallel programs will address the needs of both crop and livestock producers, along with opportunities to better integrate crop and livestock systems.

It will feature the latest in application of electronic and information technologies to help grain and livestock producers learn about wireless agriculture, RFID, ISO, GIS, GPS, remote sensing and other new additions to farmers’ vocabulary.

With new requirements for unique, traceable animal identification, beef producers will be able to see first hand how they can meet the requirement and improve their herd management at the same time. Dairymen will get an update on the latest in animal record systems and learn how to make use of the information. Crop producers and ag-business retailers will be able to experience GPS guidance systems, auto-steer, and advancements in variable rate controller systems for their field operations. New developments in yield monitors, remote sensing, and other cutting edge tools will be featured.

There will be various featured presentations during the conference including keynote presentations by Fred Yoder, Chairman National Corn Growers Association and Stan Ernst, Dept. of Agricultural, Environmental, and Development Economics, OSU who will give a perspective on how technologies can be used to position agriculture to meet consumer and global trends in agriculture. Mark Junkin, CEO of ISOFarm, will present what it means to have ISO standards for agriculture and implications for computerized record keeping for meeting consumer demands and environmental protection.

The program will include presentations by university and industry experts sharing their experience with using the technology in real farm applications. The newest developments in tools and software will be available in the exhibit area, along with experts to answer questions. Bus tours of a local high-tech livestock operation will provide a chance to see the tools in action. A field tour at The Ohio State University Molly Caren Agricultural Center will provide demonstrations and hands-on opportunities for learning about the latest innovations in tools for crop production systems including a wireless crop monitoring system and a crop health sensor. An autonomous tractor designed by engineers of the University of Kentucky Precision Resource Management Team will also be demonstrated during the tour.

Advance registration will include two-day admission to the conference, handout materials, two lunches, Monday evening barbecue and entertainment, and bus transportation for the tours. The fee is $99 per person if received before July 30. Late registration and on-site registration will be $125 per person and will not guarantee a seat on the bus. Lodging is available at several local hotels and motels. Details for exhibitors, sponsorship and on-line registration are available on the conference website: Certified Crop Advisers (CCAs) will be able to earn continuing education credits for many of the sessions.

This will be the first in a new series of regional conferences modeled after the popular international InfoAg Conferences that have been organized by the Potash & Phosphate Institute (PPI) and the Foundation for Agronomic Research (FAR). This conference is jointly presented by PPI/FAR, the Ohio Agriculture Technology Association, Ohio Geospatial Extension Program, the Ohio State University Extension Precision Agriculture, the Ohio State University Extension Beef Team, the Purdue University Site-Specific Management Center, the University of Kentucky Precision Resource Management Team, and the Kentucky Precision Ag Network.

For more information, contact Harold Watters at (937) 440-3945, or Nathan Watermeier at (614) 688-3442,

Western Ohio Agronomy Field Day

The Ohio State University Extension, Stillwater Watershed and A.C.E.(Agriculture for a Clean Environment) groups are co-sponsoring the Western Ohio Agronomy Field Day on August 4, 2004. The field day will be held at the Darke County Farm located at 5105 County Home Rd. Greenville, Ohio (the farm is located at the southwest corner of St. Rt. 127 and St. Rt. 49, just south of the Darke County Jail). Register by calling the OSU Extension Office at 937 548-5215. The program will start at 6:00 p.m. with an Early Bird Sprayer Workshop, in which producers with pesticide license can receive one hour of Core Credits, additional credits will be given for category 1 (Grain & Cereal Crops) and category 12 (Seed Treatment).

Presentations will be given on; Crop Insect Up-date, Soybean Disease Up-date, and Fall Weed Control Programs and Herbicide Resistant Weeds. Following the presentations a walk-around of the on-farm research plots will be conducted.
Research plots on the Darke County Farm include: 30 inch row corn compared to Twin-row corn (twin-row corn is corn planted in 7.5 inch rows, with the twin rows being 30 inches on center). These test plots have been planted with 2 different hybrids (a tall hybrid, which does well at low populations and short, high population hybrid), at 3 different populations (30, 000 plants/acre, 35,000 plants/acre and 40,000 plants/acre).

Intellicoated Corn Test Plots were planted that compare polymer coated corn seed planted at two different dates with a non-polymer coated seed. These plots will be evaluated for stand populations and yields. An extensive corn seed treatment study was also planted with 14 different seed treatments. These plots will be studied for stand populations and yields.
In addition, a first year corn rootworm survey study will be on-going, participants will be able to observe the procedures for monitoring the corn rootworm in soybean fields and to discuss the economic importance of such a survey.

This educational program is open to the public, and will provide a unique and hands-on perspective of agronomic production in Western Ohio. CCA credits will also be provided for Certified Crop Advisors. For more information contact Steve Foster at (937) 548-5215 or email

Archive Issue Contributors: 

State Specialists: Pat Lipps, Dennis Mills & Anne Dorrance, (Plant Pathology), Robert Mullen (Soil Fertility), Peter Thomison (Corn Production), Extension Agents and Associates: Ray Wells (Ross), Greg Labarge (Fulton), Todd Mangene (Mercer), Ed Lentz (Seneca), Howard Siegrist (Licking), Harold Watters (Miami), Dusty Sonneberg (Henry), Steve Foster (Darke), and Steve Prochaska (Crawford).

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.