CMEG Crop Management Extension Group

Field Crop News

Website Address: http://fcn.agronomy.psu.edu/

September 12, 2006    Vol. 06:20

IN THIS ISSUE:

Weather Outlook — Paul Knight

Dull conditions will dominate Wednesday into Friday. The majority of the showers that fall on Wednesday will be in western and central sections with only a few in the eastern counties. Periods of rain are likely in eastern Pennsylvania on Thursday with drizzle and a few showers in central areas and mainly dry in the western section. Low clouds, morning fog and drizzle are likely in central and eastern Pennsylvania on Friday with only slow clearing. During this 3 day period, temperatures will be mainly in the 60’s. A distinct warming trend will be noticed during the weekend and into Monday. Apart from foggy mornings, afternoon readings will rise well above seasonal levels — at or above 80 degrees in many sections early next week. A cool front, with scattered thundershowers, will cross the state either later Monday or Tuesday. More seasonable conditions are expected at mid-week. The Tropics will be rather active, but no threat is anticipated for eastern North America through the weekend.

How Late is Too Late to Plant Perennial Forages? — Marvin Hall

Farmers are frequently faced with the situation of planting perennial cool—season forage crops later in the fall than is recommended. The risks of late planting must be weighed against considerations such as need for forage the following year or ground cover to comply with conservation plans. These are strong pressures on producers to assume greater risk and plant after the recommended date. Research was completed in Centre and Lancaster Counties to determine the risk of planting forage crops on different dates throughout the late—summer and fall.

Legumes (alfalfa, red clover, birdsfoot trefoil)
Delays in planting legume after August 1 reduced plant height in late—November, percent ground cover in the spring after planting, and DM yield during the year after planting. Total DM yields for the year after planting were reduced by an average of 158, 105, and 76 lb/acre for alfalfa, red clover, and birdsfoot trefoil, respectively, in central Pennsylvania for each day planting was delayed after August 1. In southern Pennsylvania, the declines in yield with delayed planting were not as pronounced. Generally, planting legumes after September 5 in central and September 30 in southern Pennsylvania resulted in total DM yields of less than one ton/acre in the year after planting.

Grasses (orchardgrass, perennial ryegrass, reed canarygrass)
Delays in planting had less effect on grass than legumes. Orchardgrass and perennial ryegrass yields did not decrease the year after planting when planting was delayed from early— to late—August. However, delays in planting after September 1 caused DM yields to decline by 100 and 153 lb/acre, respectively, the year after planting for each day planting was delayed. Reed canarygrass was more sensitive to delays in planting than the other grasses. Each day of delay in planting reed canarygrass after early—August reduced yield an average of 120 lb/acre the year after planting in central Pennsylvania. A similar pattern occurred in Lancaster County but declines in yield with delayed planting were not as pronounced as in central Pennsylvania.

Recommendations
On fertile well—drained soils, summer—seeded perennial cool—season forage legumes and grasses can persist through the winter if planted within a few weeks of the recommended optimum date. In general, planting perennial cool—season forage crops after September 5 in central and September 30 in southern regions of Pennsylvania severely jeopardizes the vigor of the seedlings and results in yields the following year that are too low for practical forage harvesting.

Fall Weed Management in Grass Hay and Pasture — Bill Curran and Dwight Lingenfelter

Fall is an excellent time to manage certain weeds in grass hay and pastures. In particular, biennials such as common burdock, wild carrot, and bull, musk, and plumeless thistles are much easier to kill while they are in the rosette stage of growth and prior to surviving a winter. Once they awake in the spring, they grow rapidly with the goal of reproducing and it becomes more difficult to control them. As you have heard many times before, late summer and fall is the best time to control most perennials with a systemic herbicide. In general, the application window runs from about Sept. 1 through October depending on where you are in the state and what weeds you are targeting. Applications to perennial species like horsenettle, smooth groundcherry, and woody species like multiflora rose should be on the early side of this window, while cool—season perennials like Canada thistle and dandelion can be effectively controlled after several light frosts. With both biennial and perennials species, adequate leaf tissue must be present and it should be reasonably healthy to absorb the herbicide.

Favorable air temperatures should be a consideration immediately before, during, and after application. In general, the warmer the better, with daytime high temperatures in the mid 50’s at a minimum. Cold nights and cool, cloudy days will reduce and slow the effectiveness of the applications. The more active the weeds are growing, the better the herbicide performance.

So, how do you decide what product (s) to choose? There are a number of systemic broadleaf herbicides for grass hay and pasture. Currently there are no products labeled for grass control in cool—season grass hay or pasture. In addition, most broadleaf weed control products will kill or injure any legume companion crops. Some should not be used on certain grass species because of injury concerns. Some products are better than others on certain weed species; some are more restrictive relative to making hay, grazing, or planting a rotational crop or over-seeding and some have manure handling precautions. And of course, products will differ in cost per acre. These are the types of questions you need to ask and answer before deciding what product (s) are best for a particular situation. Check the 2005/2006 Penn State Agronomy Guide Table 2.6—7 for specific herbicide performance by weed species information and a current product label for use recommendations and restrictions.

Here is a quick summary of the more common herbicide options.
2, 4—D ester 4E (1/2 to 1.5 pt/A) — 2, 4—D is a systemic herbicide that controls annual, biennial, and perennial broadleaves. The ester formulation is slightly more active than the amine and should not be used post—emergence if temperatures are greater than 80°F. 2, 4—D is commonly tank mixed with other herbicides (e.g., dicamba) to improve control and broaden weed spectrum. This is a good, inexpensive herbicide with limitations. It tends to be weak on a number of weed species including wild carrot, dock species, bedstraw, horsenettle, hemp dogbane, common milkweed, pokeweed, brambles and most woody perennials. It has a 7 day grazing and 30 day haying restriction. Check product labels as some restrictions/uses vary.

Clarity 4S or Banvel 4S (0.5 to 4 pt/A) — Clarity/Banvel (dicamba) is a systemic herbicide that controls many annual and biennial broadleaf weeds and provides suppression or control of numerous perennials. Clarity/Banvel is commonly tank mixed with other herbicides (e.g., 2, 4—D) to improve control and broaden weed spectrum.

Overdrive 70WDG also contains dicamba in addition to diflufenzapyr (a synergist) and can be used in established grass stands (not seedlings) for control of numerous broadleaf weeds. The Overdrive use rate is 4 to 8 oz/A and can be tank mixed with numerous herbicides. Dicamba is fairly broad spectrum but tends to be weak on wild carrot, buttercup species, dandelion, milkweed, and bedstraw to name a few. At 1 to 2 pints/acre, dicamba has a 21 day grazing and 51 day haying restriction. Overdrive does not have any grazing or haying restrictions.

Cimarron 60DF (0.1 to 1 oz/A) — Cimarron (metsulfuron-methyl) is an ALS—inhibitor herbicide that controls many annual, biennial, and some perennial broadleaf weeds, depending on the rate used. It can be used in established warm or cool season grass stands. For most grass species, do not apply until one year after establishment (minimum of 6 months); timothy and fescue require a longer period. It is often tank mixed with 2, 4—D or dicamba to increase activity and weed control spectrum. This combination provides good control of weeds like Canada thistle, bull, musk, and plumeless thistle, and multiflora rose to name a few. COC or NIS must be included in the spray solution. Cimarron does not have any grazing or haying restrictions.

Crossbow 3E (1 to 4 qt/A) — Crossbow is a systemic herbicide that contains triclopyr plus 2, 4—D ester. It can be used on established cool or warm season grass stands for control of a variety of annual, biennial, and perennial broadleaf weeds and is also effective on woody plants and brush. Crossbow is often the standard product used for bedstraw control but is only fair on Canada thistle. For lactating dairy, do not graze until the following spring, while there are no grazing restrictions for other livestock. Crossbow has a 14—day interval between application and haying.

Stinger 3E (0.33 to 1.3 pt/A) — Stinger (clopyralid) is systemic and controls certain broadleaf weeds and is especially effective on thistles (Canada, musk, bull, etc.) and other aster—family species. It can be used on established warm or cool season grass stands. Stinger is more cost effective when used as a spot treatment. Stinger has no grazing or haying restrictions. Curtail 2.38L (2 to 4 qt/A) contains clopyralid + 2,4—D and is labeled for permanent grass pasture. Curtail controls a wider range of broadleaf weeds and may be more cost effective than Stinger. Do not graze lactating dairy for 14 days and do not cut treated grass hay for 30 days after using Curtail. For both Stinger and Curtail, special manure handling precautions are recommended to prevent injury to sensitive broadleaf plants (see label guidelines).

Milestone 2L (3 to 7 fl oz/A) — Milestone (aminopyralid) is a newer active ingredient (related to Stinger) labeled for grass hay and pasture. Milestone controls many annual, biennial, and perennial broadleaf weeds and is effective on thistles (Canada, bull, musk, plumeless), burdock, dock species, bedstraw, horsenettle, knapweed, sowthistle, ironweed and others. It is less effective on wild carrot, hemp dogbane, common milkweed, and most brush species to name a few. Milestone can be tank—mixed with other herbicides and the addition of NIS is recommended to enhance activity. Milestone is non—volatile. ForeFront R&P 3L (1.5 to 2.6 pt/A) is a premix of aminopyralid plus 2,4—D that can also be used in grass hay and pasture to broaden the spectrum of activity. Milestone has no grazing or haying restrictions, while Forefront has a 7 day haying restriction. For both Milestone and ForeFront, special manure handling precautions are recommended to prevent injury to sensitive broadleaf plants (see label guidelines).

Sorghum—Sudangrass Fall Harvest Concerns — Paul H. Craig

Sorghum sudangrass hybrids have gained in popularity in recent years. At this time of year many questions are asked about fall harvest concerns. Sorghums, sudangrasses, wild cherry trees and a few other plants contain a compound called dhurrin, which can lead to the accumulation of cyanic compounds. Most commonly, these compounds form hydrocyanic acid (HCN) also called Prussic Acid. Sorghum has the highest level of dhurrin, sudangrass the least and crosses have intermediate levels. There are considerable variety differences across all sorghum species. Within a few hours of frost, prussic acid can accumulate in damaged leaves. If consumed by grazing animals or chopping, the cyanide enters the blood stream and interferes with the normal use of oxygen by body tissues, causing an increased respiration rate and infrequently death.

An interesting note of the sorghums and sudangrasses is that the compound dhurrin is present throughout the growing season. Potential problems can arise even without a frost. Dhurrin is highest in young plants. For this reason the suggestion is always to never graze sorghum—sudangrass hybrids until they are at least 30 inches tall. High levels of nitrogen have also been associated with higher dhurrin levels.

Here are some suggestions from Iowa State University on managing SS hybrids. Never graze new plant growth. Make sure grazing animals have limited access to pastures and are removed from the paddock before regrowth is started.

When harvested as silage or hay, the prussic acid will be lost slowly as a gas. Most silage is expected to be safe at 6 to 8 weeks. HCN can accumulate in fresh green chop. Only chop enough of this forage to feed within a few hours. Do not allow forage to remain in feed wagons or bunks overnight.

SS that is taller than 30 inches will be safe to graze or harvest approximately 5 to 6 days after a freeze. Shorter forage, less than 30 inches, will need 10 to 14 days due to higher initial levels of HCN in the shorter plants. If the frost did not completely kill the plants, wait until the killing frost does come and then wait 10 to 14 days more. If you are worried, you can have forage tested at many forage testing laboratories.

For additional information, check out these web sites:

Wheat and Barley Planting Just Around the Corner — Erick De Wolf & Greg Roth

Timely establishment of winter wheat and barley is an important part of small grain production in Pennsylvania. Plants with 2—3 tillers in the fall have the best chance of winter survival and will yield well the following spring. Good stand establishment begins with determining the lime and fertilizer needs for your fields. Specific recommendations for wheat and barley include maintaining the soil pH between 6.0—7.0 and the application of up to 15 lbs. of nitrogen and all the phosphorus and potassium prior to planting to help ensure rapid establishment and fall tillering.

The recommended planting dates for barley and wheat are just around the corner and some areas of PA could be planting next week. However, it is important to not “jump the gun“ on this one. Planting before the recommended dates in your region often does not translate into yield and in may cases will increase the risk of diseases including barley yellow dwarf virus, wheat streak mosaic virus, and powdery mildew. The recommended planting dates are summarized below. More detailed information is also available in the Penn State Agronomy Guide.

Recommended planting dates for Pennsylvania
Pennsylvania Region Barley Wheat
Northern Sept. 10-20 Sept. 20 - Oct . 3
Western and Central Sept. 15-25 Sept. 25 - Oct . 8
South Central and Eastern Sept. 30 - Oct . 5 Oct. 1 - Oct. 15

Flying on Cover Crops — Sjoerd Duiker

In parts of the Commonwealth cover crops are being flown onto standing crops. This technique enables farmers to establish cover crops into standing crops, thereby allowing the cover crop time to get established before winter. Flying on cover crops is a method of broadcasting. Typically, therefore, seeding rates should be twice those used when drilling cover crops because of less ideal seed—to—soil contact. Low cost seed should therefore be used. The seeds should also readily germinate at the soil surface. Cover crops that are commonly flown on are rye, wheat, barley and oats.

One of the most common crops where cover crops are flown on is soybeans. The cover crops should be flown on just before leaf drop, when the soybeans begin to yellow. The fallen soybean leaves cover the cover crop seed, thus providing a microclimate that enables the seed to germinate and develop roots that grow into the soil. Once the cover crop roots are anchored, the cover crop is basically established. Spreading cover crops before yellowing of soybean leaves, or after the majority of leaves have been dropped, is less successful because the microclimate is not as favorable for seed germination. This is the reason that spreading cover crop seed in corn may not be as successful as in soybeans.

Two methods of flying on cover crops are distinguished: airplane or helicopter. Airplanes spread cover crop seed quickly but may have limited capacity. A nearby airport or landing strip is needed to load new seed into the airplane. Helicopters don’t have this problem. They can land near the field where seed can be loaded. Sometimes, a detachable hopper is used which hangs below the helicopter: if two hoppers are brought, one can be charged on the ground while the helicopter spreads seed with the other unit. Helicopters also work better in smaller fields or where fields are surrounded by trees.

One thing to consider is that neighbors may be alarmed when they see airplanes or even helicopters spreading something unknown near their homes. It may therefore be advisable to inform local police or the neighbors, if farmers decide to fly on cover crops.

Fall and Winter Manure Application Considerations — Douglas Beegle

Spreading manure in the fall and winter months requires you to consider some additional factors. First, when will the manure nutrients be used? The best nutrient utilization will come from applying the manure as close to the time of crop uptake as possible. For example, if manure is applied early in the fall to a crop like grass hay or a winter grain, the N available from that manure will be much higher than if the manure is applied at the same time and in the same way but for corn the following summer.

How you apply the manure can also make a big difference in nutrient availability. It is well known that incorporating manure as soon as possible after application will conserve the most N in crop available form. Where possible, try to get the manure incorporated. This is especially important for manure applied early in the fall and late in the winter when it is still relatively warm. Later in the fall and winter when temperatures in the surface soil fall below 50°F the potential volatilization losses are less and thus incorporation is less critical. There is however, a significant potential for losses of surface applied nutrients in runoff under these conditions. The best approach would be for producers to avoid applying manure to frozen, snow covered soils but this is not always practical. In the winter try to select fields and timing of application based on minimizing the potential for loss. Stay away from sloping areas, especially near water. Use level fields as far from water as you can at this time.

Try to plan ahead so that you will have appropriate fields available when winter conditions limit your spreading options. Don’t spread all of your level fields in the fall so that you only have the sloping fields left in the winter. Select fields with high residue levels or other cover. Try to avoid spreading manure when rain or melting conditions are expected. If you can avoid it, do not spread on deep snow.

Even if manure is applied appropriately, incorporated where possible, in good locations over the fall and winter, you are still not out of the woods because a large portion of late fall and winter nutrient losses from manure begin when conditions warm up in the spring. For example, in a corn system the manure nutrients will often remain pretty stable over the winter but soils will warm up enough early in the spring for N to become active and thus susceptible to loss long before the corn crop needs much N. Therefore even though you may have done a good job of conserving the nutrients at application time, there is still a long period of conditions favorable to N loss before the corn needs the N.

In grass hay or small grain fields these crops will begin to grow about the same time the N becomes active and will utilize the nutrients. In a corn system, cover crops can double the recovery of manure N applied during the fall and winter. When the cover crop begins growing the N is becoming available and the cover crop will utilize the N and retain it. The N will not be susceptible to loss. When the cover crop is killed or tilled the N will be released, closer to the time of corn need. See Table 1.2—14 in the Penn State Agronomy Guide for more details on manure N availability throughout the year.

To summarize, for fall and winter manure application consider applying to crops that will use the nutrients in the fall and early spring. Use cover crops where manure is spread in the fall or winter for next year’s corn. Incorporate, if practical, especially for early fall or late winter applications. Avoid spreading in obvious high loss potential situations such as frozen, snow covered, and sloping fields as much as possible. Take the time to plan ahead for winter manure applications.

Contributors: State Specialists: Dr. Doug Beegle, Dr. Marvin hall, Dr. Sjoerd Duiker, Dr. Erick DeWolf, and Dr. William Curran. Extension Educators: Mena Hautau (Berks), Paul Craig (Dauphin), Del Voight (Lebanon), and Craig Williams (Tioga)

Editor:Paul H. Craig. Senior Extension Educator, Dauphin County

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