Agriculture Weekly News Column

April 14, 2008
Nitrogen Concerns in Wheat

The wet spring has generated a lot of discussion about getting nitrogen on the winter wheat crop. Producers still have time to apply their spring topdress of nitrogen. Ohio State University research has shown that yields are not affected by delayed nitrogen until after early stem elongation (generally the end of April). Studies over the last five years have shown that yields were the same or slightly better when a single application occurred at Feekes 6 (first node visible of early stem elongation) compared to initial greenup. Yields dropped 10 – 15% when a single application was delayed to early boot stage.

Wheat

Ohio State University Agronomists Robert Mullen and Edwin Lentz recommend that producers apply N as soon as field conditions allow application equipment and that there is no need for more expensive aerial applications. Since we are applying N between initial greenup and early stem elongation, any nitrogen source would be appropriate, so selection should be based on cost and availability.

Some producers who had applied N in February have asked whether there are any tests they may use to check the N status of their plants at this time (concerns that the N may have been lost). Unfortunately there are no definitive tests. Tissue analysis is a relative test and not a procedure used to make N recommendations. A producer may topdress a wheat strip in a field with extra N now and then later use a chlorophyll meter to compare to the rest of the field at early stem elongation. The meter will qualitatively detect differences and assist in a best guess look. However, even if a significant different green color is observed or detected, a producer will not be able to determine how much more to apply based on research information.

Preplant Herbicide Applications
Spring has sprung in Union County! The recent warmer weather has caused summer annual weeds such as giant ragweed, lambsquarters, Atriplex, and prostrate knotweed to start to emerge in central Ohio. The emergence of these weeds increases the need for appropriate preplant (burndown) herbicide mixtures in no-tillage crops. With few preplant herbicides applied to date due to cold and wet soil conditions, questions are being asked about the importance of 2, 4-D in preplant herbicide applications.

Because of the prevalence of dandelion and glyphosate-resistant weeds such as giant ragweed, marestail (horseweed), common ragweed, and lambsquarters in Ohio no-tillage fields, Jeff Stachler, Ohio State University Research Associate , indicates the addition of 2,4-D in preplant herbicide applications is very important in achieving effective weed control prior to planting. At this point in the season, it is more important to include 2, 4-D in preplant herbicide applications and to delay planting of corn and soybean rather than planting the crops and controlling weeds after planting. We will continue to monitor weather conditions and weed populations and recommend appropriate preplant herbicide mixtures as the season progresses.

2008 Soybean Aphid Prediction
As you are likely aware, the predicted soybean aphid outlook was that 2007 should have been a banner year for the pest. Instead, we had an early April freeze that killed most of the aphids which resulted in very few problems in 2007. Ron Hammond, Ohio State University Entomologist, who studies the soybean aphid, saw very few aphids or eggs on buckthorn last fall. Very few winged aphids were caught last fall in states surrounding Ohio.

The 2008 prediction is for very few aphid problems in Ohio for the summer of 2008. Although there are really no preventive treatments for soybean aphid, it will be nice of producers don’t have to be concerned with this pest this summer. Make sure, however, that you scout the 2008 crop, pay attention to state scouting reports, as well as local reports on insect pest for this year’s soybean crop. As you know, Mother Nature has a way of keeping us humble when we try to out-guess her!

Ohio Largemouth Bass Workshop
For those of you who have an interest in unusual enterprises, you may want to attend the Ohio Largemouth Bass Workshop which will be held on Saturday, April 19, 2008, from 8:30 a.m. until 4:00 p.m. The workshop will be held at the Fisher Auditorium on the campus of the Ohio Agricultural and Research Development Center in Wooster.

Largemouth bass are becoming an increasingly popular aquaculture species. While they have always been in demand for sport fishing, there has been a recent increase in the demand for largemouth as a food fish, particularly in Ethnic markets. Ohio is currently 4th in the nation in pounds of largemouth bass produced.

The workshop will cover the basics of what it takes to produce largemouth bass in Ohio from reproduction to marketing. Researchers from Kentucky State University, the leading largemouth bass research center in the country will be sharing their culture procedures and recent research findings.

To register, call Julie Strawser at 740.289.2071 at extension 223 or e-mail her. Call Ohio State University Extension, Union County at 937.644.8117 or 800.589.8584 for her e-mail address.

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April 21, 2008
CORN Newsletter

Many of our readers subscribe to the Crop Observation and Recommendation Network Newsletter. This newsletter is written weekly during the growing season. It is a compilation of crop scouting, review of crop conditions, and production recommendations. It is timely, as it is written after a statewide phone discussion each Monday, and is available on Tuesday each week.

The newsletter is available on-line (an e-mail reminder to access it), or for those who prefer in hardcopy. To subscribe, contact Ohio State University Extension, Union County at 937.644.8117 or 800.589.8584 or by email. If you are currently not receiving CORN, you will find it to be very useful as a valuable resource.

Managing Your Soybean Seed Supply

Ohio soybean growers that have their sights set on increasing soybean acreage this year may face crop production challenges due to less than optimum seed quality. Several weeks ago we reviewed the soybean seed quality situation. As fields are drying out, a reminder will encourage you to evaluate your seed quality before making final planting plans.

As most of our readers are aware, soybean seed production fields were harvested last year when the seed was large and very dry, resulting in thin seed coats. This seed can be easily damaged, translating into potentially lower germination rates, along with reduced vigor and quality, and a higher chance for disease development with some soil types. It is a concern for heavy clay soils and in those fields that have had a history of replanting issues that lower quality seed is not going to do well. The reason being is that the seed coat is already thin and as it rains during the spring the seed will swell and split. All the good stuff in the seed will begin to leak out and when that happens all of the pathogens that are common to our soils will get excited. These pathogens can find the seed faster and we have more seed rot and seedling disease.

Anne Dorrance, OSU Extension Plant Pathologist and OSU Extension Soybean Agronomist, Jim Beuerlein, encourage growers to return to the basics of crop production when it comes to handling poorer quality seed and ensuring a profitable crop stand this season. They off the following tips for managing seed supply:

All seed should be treated with fungicides for protection from root rot diseases. This situation is the exact reason why we have fungicide treatments. Treating may reduce the germination a bit, but should increase final stands and root system health.
Plant the highest quality seed first and in the most adverse environments. Watch the weather, and plant the highest quality seed under the worst conditions, because it already has a good start. Seed that isn’t as good in quality should be planted under more favorable conditions when you know that it will be dry for a few days after planting. It won’t do a grower any good to put poor quality seed in the ground to beat a rain storm and then get dumped with two inches.
Handle the seed as gently as possible. If you’ve got a bag of seed and seed germination of 80 percent that means you’ve got to be careful. The seed is fragile and will split more easily, so you do not want to throw that bag of seed around.
Adjust seeding rates. Pay attention to how much seed is going into the ground. On one hand, Ohio producers tend to over-seed, and for those who do, you may end up with a good stand. But for those growers who try to stretch the seed across their acres, they may want to bump that seed count up.
Slow the planter down so that each seed is planted 1 inch to 1.5 inches deep and spaced uniformly in the row. If you must reduce seeding rates, it is much better to have low populations in narrow rows than wide rows.

According to the U.S. Department of Agriculture, Ohio growers intend to plant 4.5 million acres of soybeans this year, up from 4.1 million acres last year, and slightly lower than the 4.6 million acres planted in 2006. Indiana producers are expected to raise soybean acres by 800,000. With the increased soybean acreage, Dorrance said that fears of a potential soybean seed shortage are warranted. The concern is that if we end up in trouble due to seedling diseases there may not be enough seed for replanting. Conditions in Ohio are very favorable for these soil-borne diseases.

Applying Wheat Herbicides in 28% How Late is Safe?
Since wet weather has prevented traffic in many wheat fields, applications of herbicides and nitrogen fertilizer may occur when wheat is at a more advanced growth stage compared to some other years. Be sure to stage wheat prior to herbicide applications, and consult the “Weed Control Guide for Ohio and Indiana” and herbicide labels for information on herbicides and growth stage. One of the questions relative to this subject is – how late in spring can wheat herbicides be applied using 28% UAN as the spray carrier? Stated another way, does application of herbicide in 28% UAN increase the risk of wheat injury and yield loss compared with application in water, when wheat is advanced in growth stage? Mark Loux, Ohio State University Extension Weed Specialist, addresses the concerns to be aware of as you make wheat herbicide applications.

Herbicide labels often do not provide much information on application in 28% UAN. Ohio Sate University conducted one study on this in 2003, where various herbicides were applied in water or 28% when wheat was in the joint or boot stage. Herbicides applied included Harmony Extra, 2,4-D amine, Buctril, and Harmony Extra plus 2,4-D amine. None of the herbicides reduced wheat yield when applied in water or 28% UAN on April 16 to wheat in the joint stage.

The major treatment effect observed for applications made to wheat in the boot stage on May 9, was a yield loss of about 20% when Harmony Extra or Harmony Extra plus 2,4-D was applied in 28% UAN. Aside from this, for the May 9 application, there was a trend for minor yield loss with the combination of Harmony Extra plus 2,4-D applied in water, and Buctril applied in 28% UAN. Keep in mind that the wheat growth stage on May 9 was far enough advanced that several of these herbicides should not have been applied in water or 28% UAN. For example, 2,4-D labels specify application to wheat prior to joint or boot stage, depending upon the product.

These results indicate that wheat should tolerate application of herbicide in 28% UAN well into April, as long as the restrictions on herbicide labels relative to what growth stage are followed. For products that applied with surfactant, consult labels about the surfactant rate when applying in water vs 28%, since surfactant rates may be reduced to minimize the risk of injury when applying in 28% .

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April 28, 2008
Burndown Herbicide Treatments - Can You Afford Not To Use 2,4-D Ester?

The weather has been up to now less than ideal for field activities, and many no-till fields that would have typically received a preplant burndown herbicide treatment by now remain untreated. The delay in treatment is in itself not necessarily an issue for control. Although weeds get larger and vegetation becomes denser with delays in treatment, a well thought out mixture of herbicides will still provide the needed control. In our experience, a combination of glyphosate and 2,4-D ester will typically be effective into early May or later in no-till fields. The bigger issue here is that when soil conditions prevent traffic until late April, planting and burndown applications tend to occur at about the same time in some fields. This often leads to omission of 2,4-D ester from burndown programs, especially in soybeans, because it’s not always possible to wait the required 7 days between 2,4-D application and soybean planting. Mark Loux, Ohio State University Weed Specialist, provides the following suggestions on the importance and use of 2,4-D in spring burndown applications.

The importance of a “clean” start in no-till fields cannot be emphasized enough The most effective weed control and highest yield potential results from using fall or spring burndown herbicides, and establishing the crop under weed free conditions. Failure to use an effective burndown treatment that includes several different herbicide sites of action also increases the risk of herbicide resistance. The advantages of 2,4-D must be weighed against the delay in planting as a result of its use.

Keep in mind that the inclusion of 2,4-D ester in burndown programs can help control a number of large or tough winter weeds, including marestail, dandelion, wild carrot, poison hemlock, mustards, etc. Adding 2,4-D to glyphosate-based burndown programs also greatly reduces the selection for glyphosate resistance in early-emerging summer annuals, including marestail, lambsquarters, and giant and common ragweed. Populations of these weeds have already developed resistance to glyphosate in Ohio fields, and some of the glyphosate-resistant ragweed populations have resistance to ALS-inhibiting herbicides also. Our research shows that control of resistant populations in soybeans can be almost impossible unless the field is weed-free at the time of planting, and use of 2,4-D ester is required to achieve this where glyphosate resistance has developed.

For a review of the guidelines for 2,4-D ester use in no-till corn and soybeans follows, call the Extension Office or go to http://agcrops.osu.edu/.

Winter Injury in Alfalfa
With reports coming in about winter injury in alfalfa, now is the time to check your stands for damage. Injury reports range from heaving to outright winter kill of plants without heaving. Considering the stressful conditions last year and through the winter and cutting management decisions that were made late last fall, the reports are not surprising. Mark Sulc provides an update on the alfalfa situation.

The 2007 Easter freeze followed by very dry conditions the remainder of the growing season left alfalfa stands in a weakened state going into the winter. Where a late fall harvest was made, no plant cover was left to insulate the crowns and the soil from alternative freezing-thaw cycles. Research in Wayne County demonstrated that early November harvests dramatically increased heaving in alfalfa stands compared with where a late harvest was not made. Furthermore, very wet soils throughout the winter probably contributed to lack of oxygen for alfalfa roots, and wet soils are also known to decrease cold tolerance of alfalfa.

A careful inspection of all alfalfa stands at this point in time is very important. A “windshield inspection” is not enough to accurately assess the health of alfalfa stands this year. Walk your fields and get a broad view to determine whether spring growth appears uniform. If growth is spotty or nonexistent, it is very likely that plants have suffered severe winter injury or heaving.

Heaving in alfalfa stands has been reported from north to south in Ohio and in older as well as newly seeded fields. Severity ranges from mild to severe, both within fields and between fields. Heaving is usually more severe in areas with less than ideal internal and surface soil drainage, which includes much of Union County.

Plants with crowns heaved up 2 or more inches are already dead, or are in the process of desiccating and will soon die. Plants that are heaved 1 to 1.5 inches above the soil surface or less may on casual inspection appear normal and healthy with decent spring growth. But closer inspection may reveal some moderate heaving, which will likely limit the productive life of the plant. Such plants will desiccate more quickly, be injured by wheel traffic, and crowns may break or be cut off at the first harvest. Some of those plants may survive through the first harvest, but their yield potential is compromised and they will likely disappear from the stand at some point during the growing season.

Plants can also be killed by cold temperatures. Winter killed roots will have a gray, water-soaked appearance early, just after soils thaw. Once water leaves the root, the tissue will become brown, dehydrated and stringy. If the root is soft and water can be easily squeezed from it, or is brown, dry and stringy, it is most likely winter killed.

To evaluate an alfalfa stand, estimate the number of live plants per square foot. The best way to do this is to dig up and count the plants in a 1 to 2-square foot area in several parts of the field. Second year stands (seeded last year) should have 10 to 12 plants per square foot, and third year or older stands should have 5 to 6 plants per square foot for optimal yield potential. When making plant counts, consider only those plants that appear healthy with vigorous shoot growth.

Carefully evaluate the condition of new buds and new shoots for evidence of injury. Healthy plants with no winter injury will show vigorous, symmetrical growth all the way around the crown. Injured legume plants will often show asymmetrical growth caused by injury to part of the crown.

Take a random sample of the plants that were dug up for making stand counts. Split the taproots lengthwise to look for internal discoloration of the taproot tissue. Healthy taproots will be firm and creamy white. Root and crown rot will appear as various darker shades. The degree of root and crown rot affects plant productivity, vigor, and long-term survival. If taproots are watery, tan or yellow, or already desiccating, it is an indication that freeze injury has occurred and the plants will likely die.

Visually estimate the ground cover of desirable forage plants as the stand develops 4 to 6 inches of new growth. Stands with more than 80% ground cover and good vigor will produce excellent yields, stands with 60-80% ground cover should produce fair yields, stands with 40 to 60% ground cover will probably produce yields in the 60% range of normal, and stands of 20-40% ground cover will yield less than half their normal potential. Weeds will become a real problem in the thinner stands, and over seeding with grass or destroying the stand and rotating out to another crop should be considered.

Check Wheat Stands

Before applying any additional nitrogen or herbicide to wheat, growers should first assess the crop’s growth stage. Growers concerned about the state of their crop should also conduct a stand count in fields or sections of fields that may exhibit problems.

You may want to go out and count the tillers in poor-looking areas of their field. Fifteen tillers per-foot-of-row is considered minimum for an economic crop. The number of tillers on the wheat determines yield potential, and yields are reduced if tiller numbers fall below 25 per square foot after green-up.

Growers should then assess the crop’s growth stage by pulling multiple tillers in multiple areas in the field, stripping off the lower leaves and looking for the first node. The wheat is at growth stage six. Growers need to identify the growth stage because most of the critical management decisions with fungicide, herbicide and insecticide applications all depend on specific growth stages.

In general, herbicide applications should be made before the first node develops. Remember, short-looking wheat does not mean that the crop is not developing and advancing through the different growth stages. Growers who rely on the height of the crop as an indicator of crop development may be missing a critical growth stage for herbicide application.”

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