CMEG Crop Management Extension Group

Field Crop News

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

August 21, 2007    Vol. 07:25

IN THIS ISSUE:

Weather Outlook — Jeff Warner, Pennsylvania State Climatologist

While the rains of recent days have certainly provided some much needed moisture, the next couple of weeks look to return to relatively warm and dry weather with a much lower threat of showers and thunderstorms as disturbances pass. The end of the first week looks particularly warm and humid with a threat for some mainly afternoon thunderstorms. Much of next week will also be warm, before slightly cooler air arrives toward the first weekend of September.

Week One (Aug 22–29): The cool weather will continue for Wednesday and Thursday, especially across the eastern part of the state, as breezes from the east draw unseasonably cool air inland from the ocean. By Thursday, warmer air returning to the state will spark some showers and thunderstorms, especially during the afternoon and evening. By Friday, it will turn much warmer and more humid, with temperatures climbing toward 90 degrees. While an isolated storm is possible on Friday or early on Saturday, the greatest threat for storms does not appear to return until late on Saturday or Sunday. Next Monday and Tuesday look to remain warm, sunny and mainly dry.

Week Two (Aug 29–Sept. 4): The middle of next week will remain rather warm while the humidity will gradually return to the state as well. The risk for rain will increase by Thursday and Friday as a front approaches from the northwest. Some briefly heavy rains are possible as the disturbance passes. It should turn slightly cooler for the weekend, before the warm weather looks to build again early in the first week of September as sunshine and drier air returns to much of the state.

Check out the predicted Growing Degree Days (base 55) for Pennsylvania for the next two weeks at: http://climate.met.psu.edu/data/regional_gdd.php

PDA Market Prices — Tom Murphy, Lycoming County Extension

Southeastern Pennsylvania
Grain Range Avg Contract for Harvest
Corn No. 2 3.78-4.20 4.02 3.45-3.56
Wheat No. 2 6.05-6.37 6.17 5.09-5.23
Barley No. 3 2.70-3.15 2.88 2.50
Oats No. 2 2.60 2.60 ---
Soybeans No. 2 7.64-7.68 7.65 7.82-7.98
*Gr. Sorghum --- --- ---
Ear Corn 105.00-118.00 112.25 ---
Western Pennsylvania
Grain Range Avg
Corn No. 2 3.60-3.90 3.72
Wheat No. 2 5.67-6.00 5.83
Barley No. 3 --- ---
Oats No. 2 1.85-2.50 2.12
Soybeans No. 2 7.23-7.75 7.49
Ear Corn 115.00 115.00
South Central Pennsylvania
Grain Range Avg
Corn No. 2 3.80-4.03 3.92
Wheat No. 2 5.00-5.45 5.27
Barley No. 3 2.75-3.35 3.01
Oats No. 2 2.40-3.00 2.56
Soybeans No. 2 7.30-7.80 7.60
*Gr. Sorghum --- ---
Ear Corn 100.00-140.00 117.37
Central Pennsylvania
Grain Range Avg
Corn No. 2 3.80-4.10 3.99
Wheat No. 2 6.22 6.22
Barley No. 3 2.65-2.90 2.75
Oats No. 2 2.30-2.50 2.42
Soybeans No. 2 7.66-7.80 7.76
Ear Corn 105.00-119.00 114.00

The Late Season Corn Stalk Nitrate Test — Doug Beegle, Soil Fertility and Nutrient Management Specialist

Nitrogen (N) management is one of the most difficult decisions in corn production because of the many factors that influence N behavior including: materials, timing, weather, etc. This is especially true when manure is part of the system. Standard recommendations try to account for many of these variables and early in—season tests such as the Pre—sidedress Soil Nitrate Test (PSNT) and Chlorophyll Meter test are very helpful in reducing the uncertainty in N recommendations. While we can never totally eliminate this uncertainty, with experience we can minimize it. A key to improving N management over time is having reliable feedback on how well your N management is working. Good yields and dark green plants are certainly good indicators of adequate N but they do not tell us if we have too much N, which can be a problem especially with manure. Also, some visual symptoms of N deficiency late in the season may not always indicate a yield loss.

The Late Season Corn Stalk Nitrate Test has been shown in research at a number of locations, including across PA, to be a reliable end of season indicator of crop N status. It provides a good assessment of whether the crop had the right amount of N or too much N or whether it ran out of gas. This information combined with records of N management can be very useful for making future management decisions.

To do this test, 8—inch long sections of corn stalk (subsequently cut into two inch long segments) are taken starting 6 inches above the ground. Pruning shears usually work well for taking these samples. Stalk sampling can be done anytime between about the ¼ milkline stage of the grain, which is just before silage harvest and up to 3 weeks after the grain forms a blacklayer. If possible, dry the samples immediately or send them to the lab as soon as possible after collection. If there is more than a day between sampling and sending, refrigerate (don’t freeze) the samples until you can send them. Keep the samples in paper (not plastic) bags. While you could test all fields, testing a few representative fields will probably be adequate to provide a good assessment of your N program. Detailed instructions and submission forms can be found at http://www.aasl.psu.edu/Corn_stalk_nitrate.html

This test is available through the Penn State Agricultural Analytical Services Laboratory (AASL). The cost of this test is $10. Additional information is available on the AASL web site at: http://www.aasl.psu.edu/. Results of this test provide a good assessment of the adequacy of the nitrogen management in a field and can be very helpful in adjusting management in the future.

Organic Matter, Soil Carbon Sequestration, No—till, and Global Warming — Jeffrey Graybill, CCA Lancaster County

Farmers know that with respect to soil productivity, increases in organic matter (OM) yield many benefits. The dark color (OM) that decomposing manures, cover crops and residues add to the soil will increase the fertility and quality of our soils. Soils in the Capital region and most of PA typically have 2 – 3% OM. This is a small but very important portion of the soil, even small increases in OM will have a large impact in our crop production. This is because organic matter is the most important component in maintaining a healthy productive soil.

Benefits of soil OM include: Improved Soil Structure, Resistance to Compaction, Reduced Runoff and Erosion, Energy and Food for Soil Microbes to thrive on, Increased Nutrient Holding Capacity (cation exchange capacity— CEC), and Increased Water Holding Capacity. One proven way to manage and increase soil OM is through no—till and conservation farming. Excessive tillage aerates the soil, mineralizing the OM which then is released as carbon dioxide (CO2). This burst of biological activity also results in a flush of nutrients being made available to the crop, but only occurs for a limited time. In no—till production, the release of nutrients is controlled and continues throughout the growing season thus maintaining not depleting soil OM.

Carbon, organic matter and CO2 are all inter—related terms. OM is primarily composed of carbon; when soil microbes digest manures and soil OM, they release nutrients to the crop, but they also release carbon in the form of CO2. Carbon sequestration is simply the increase in soil OM (soil carbon) through the addition of crop residues, cover crops and manures to our farmland. Through no—till and conservation farming systems we are removing CO2 from the air, incorporating it into crops and moving it into the soil where it is stored as organic matter.

Could there be global benefits to No—till crop production? Current research estimates vary; but one reputable study by the Oak Ridge National Laboratory (Author: T. O. West; averaging 9 experiments together) found an average increase of approximately 600 lbs of carbon per acre per year in no—till farming systems. To quote this article: “Agricultural ecosystems have the potential to sequester carbon dioxide from the atmosphere and partially mitigate global climatic change.”

So what? Well; it would appear that not only can no—till crop production enhance our soil health and productivity; but, if practiced across a wide area could help address rising CO2 levels and even help slow global warming.

Sprayer Retrofit Twilight Meeting — Mena Hautau, Berks County Educator

A Sprayer Retro—fit Twilight Meeting was held August 16 at J & R Kulp Farms, Hatfield, PA with about 55 growers present. The goal of the event was to update growers on current sprayer technology and to demonstrate tools that can improve coverage. The bottom line is that pesticides cost a lot of money and growers want good results from using these materials. Reducing drift is a big concern for many growers who farm near urbanization. Growers can and should retrofit and update their sprayers to meet these needs. A boom sprayer, owned by the Kulps, had been retrofitted with quad nozzle bodies this past spring. The sprayer tips demonstrated included twinjet, turbo twinjet, air induction, turbo floodjet and an XR teejet. The quad nozzle bodies help growers make choices about what kind of nozzle to use under varying conditions, with minimum effort. Using water, growers could see the differences in the spray pattern, as the sprayer operated, especially in wind gusts. Water was collected in a spray pattern table, resulting in an even spray pattern from nozzles that are not worn out. Water sensitive card, placed in the upper and lower soybean canopy, were used to show the variation in crop coverage with different nozzles and pressures. Also, cards were placed outside the canopy to show how pesticides drift away from the field. The meeting was sponsored by the Southeast PA Crops Conference partners, in cooperation with Penn State Extension.

Mile—a—Minute Weed — Melissa Bravo, PA Dept of Agriculture

Mile—a— minute (Polygonum perfoliatum) is an introduced annual vine from eastern Asia that has become a widespread weed in Pennsylvania and neighboring states. This plant is considered an invasive, noxious weed because its aggressive growth allows it to out compete and displace native plants in many habitats and the barbed vines and dense vines impair recreational use of streams.

The first establishment of mile—a—minute in the United States was in Pennsylvania, where an infestation was discovered in 1946 at a nursery in York County. This infestation was likely a result of contaminated rhododendron nursery stock imported from eastern Asia in the late 1930’s. The Pennsylvania Department of Agriculture added mile—a—minute to the Noxious Weed Control list on May 20, 1989. At this time the infestation had already spread across 5 counties. As of 2005, mile—a—minute is widespread and prolific in 30 counties, primarily the counties below interstate 80. Currently, mile—a—minute is not found in counties in the first or second tier of the state with the exception of an isolated but large infestation in the Sinnemahoning Valley in Cameron and Potter County in the area of Wharton, PA. These negative counties include: Erie, Warren, McKean, Tioga, Bradford, Susquehanna, Wayne, Crawford, Venango, Forest, Elk, Clinton, Sullivan, and Wyoming. Mile a minute is known in the southern edge of Lycoming, Columbia and Luzerne and a small but isolated infestation was found in Bellefonte in Center county in 2005.

This annual vine in the buckwheat family is a prolific seed producer. Birds are the primary method of dispersal on the upland terrain while seed movement in water is the primary method of dispersal along stream banks which has resulted in the rapid colonization across the state.

For farmers, the threat of mile—a—minute to cropland comes from infestation of riparian area CREP land, vegetable and low bush fruit crop infestations and organic production. Mile a minute is not tolerant of tillage or other managed systems. PDA urges farmers to become familiar with the appearance of this weed so that when it is observed to be growing in hedgerows or along the edges of fields quick action can be taken to remove the vines. Mile—a—minute has triangular shaped leaves, recurved barbed hooks on the stem and produces blue berries which emerge in late summer. A distinctive ochrea or collar on the internodes of the stem, where the berries form, is a key characteristic of the plant. Preventing seed formation and seed dispersal is essential to controlling mile—a—minute.

PDA, DCNR and other state partners are targeting the Sinnemahonning Valley mile—a—minute infestation for eradication. The threat to the PA Wilds and streams such as Pine Creek is significant and all attempts to eradicate this weed from the northern counties should be implemented to slow the spread of this noxious vine across the rest of the state.

For a picture of the weed, please visit the following website http://www.agriculture.state.pa.us/agriculture/lib/agriculture/plantindu

Prowl H2O Application in Alfalfa — Dwight Lingenfelter, PSU Weed Science

As a reminder, Prowl H2O 3.8CS (BASF) has a supplemental label for use in established alfalfa (i.e., alfalfa that has gone through a summer season of cutting/mowing). Apply Prowl H2O at 2 – 8 pt/A prior to weed emergence. Applications can be made in the fall after the last cutting, during winter dormancy, or in the spring before alfalfa reaches 6 inches of regrowth and weeds have germinated. Prowl H2O will control many annual grasses and broadleaves including crabgrass, panicums, foxtails, lambsquarters, pigweed at the 1 to 4 pt rate. Other weeds such as annual bluegrass, common chickweed, dodder, henbit, prostrate knotweed, smartweed, and velvetleaf can be controlled with the 4 to 8 pt rate. Some stunting and yellowing to the alfalfa may occur after application. Do not apply less than 50 days prior to alfalfa harvest for forage or hay. Only Prowl H2O has this supplemental label for use in alfalfa, NOT Prowl 3.3EC.

Late Season Corn Hybrid Assessment — Greg Roth, Grain Production Specialist

Soon silage harvest will begin in earnest and soon after the seed industry will be looking to place seed orders. Now is the time to do some assessment of hybrid performance in the field. The late season precipitation should bring on some of the typical late season corn diseases. Making some notes of how your favorite hybrids reacted to these diseases might prove interesting. Also for those producers who applied fungicides at tasseling, it will be interesting to make some assessments of how well those applications performed during our season.

I’d be looking for gray leaf spot, with its characteristic matchstick gray lesions, starting on lower leaves and moving up the plant. Highest risk fields are no—till corn on corn. Heavy infestations can lead to severe stalk rot and lodging. For more information see our publication: http://pubs.cas.psu.edu/FreePubs/pdfs/UL205.pdf

Also look for Northern Leaf Spot, also known as Carbonum leaf spot in corn. This is characterized by chain link lesions and is also present in minimum and no—till situations. It tends to be more prevalent, but less damaging than gray leaf spot. Ohio State has a fact sheet on this disease: http://ohioline.osu.edu/ac-fact/0029.html

Fields with the tops dying prematurely could be an indication of anthracnose or corn borer injury. Scouting fields now can give you an indication of corn borer pressure and whether Bt corn was justified in these environments this year.

Also, I would be looking at ear development in drought stressed field and note any differences among hybrids that are apparent.

Soybean Crop and Disease Update — Greg Roth, Grain Production Specialist

The late season precipitation has definitely improved soybean growth and should result in some drought recovery for most fields. In our full season beans, we should see improved seed size and perhaps some improved retention of the late set pods. In our double crop soybeans, with delayed flowering, there could be increased pod set as a result of these late season rains.

Soybean insect pests and diseases continue to appear with spider becoming more prevalent before the last rain. Soybean aphid levels have been declining recently.

The major pathogens identified in the Soybean Rust sentinel plots this week include Downy Mildew, Frog—eye Leaf Spot, Cercospora Leaf Blight, and Septoria Brown Spot. I would be on the lookout for charcoal rot and stem canker diseases, which became prevalent last year in some areas following a drought ending rain.

Rust continues to spread in the southern states. It has now been found along the Texas—Oklahoma border, and extends east to central Mississippi. Rust is also present in several counties in northeast Oklahoma. Many Pennsylvania soybean fields are in the seed filling stages of growth, so the risk of damage from rust, even if it were to reach us sometime soon, is steadily diminishing.

Smooth Bedstraw, an Increasingly Common Weed in Pasture and Hay Fields — Bill Curran, PSU Weed Specialist

Smooth bedstraw (Gallium mollugo) is an increasingly common weed throughout the Northeast. It is a particular problem in grass and legume pasture and hay fields. Smooth bedstraw is an herbaceous perennial that tends to form patches in infested fields. Smooth bedstraw has hairless or smooth stems and the leaves are rough on the margins and arranged in whorls around the stems. Smooth bedstraw plants are generally 1 to 3 feet tall producing white to greenish flowers in June and July that mature into shiny cream colored fruit containing two seeds each. Plants may flower a second time if mowed soon after first flowering. Patches of smooth bedstraw increase in size both through vegetative growth (rhizome and or stolons) and through seed production.

Smooth bedstraw prefers moist, cool conditions, but it can tolerate drought and grows on almost any soil type. It is adapted to high phosphorus levels, so it does well on fields that regularly receive manure. The weed prefers calcium-rich neutral pH soils and high nitrogen (N), but also does well on low N and lower pH soils. The seeds are dispersed by birds, sheep and other livestock, water, contaminated crop seed and hay, and through mowing to name a few methods. Previous research has shown that the seeds do not persist in the soil much beyond one year and that they possess little dormancy. The weed typically spreads within and between fields as seed, so managing seed production is an important control tactic.

Bedstraw

Cultural management includes providing the desired forage crop with optimum conditions to be competitive and productive and not overgrazing. Supplying nutrients and lime, cutting the hay more than once per season and prior to smooth bedstraw seed production are important management tactics. Mowing will reduce the vigor of the bedstraw, but it will not control established plants. Smooth bedstraw does not tolerate tillage, but this obviously could only occur if reestablishing forages or when rotating to a different crop. Effective herbicides for control of smooth bedstraw are available for grass hay and pasture, but not grass—legume mixtures. Triclopyr, an active ingredient in Crossbow and aminopyralid, the active ingredient in Milestone and a component of Forefront can effectively control established plants. For best results, apply the herbicides at the bud to bloom stage prior to successful seed production or in the early fall after flowering and seed production have been suppressed by mowing. These herbicides will kill or injure legumes such as the clovers or birdsfoot trefoil. Consult the Penn State Agronomy Guide for more specific herbicide application rates and use restrictions.

Helpful websites:

Ohio State University — http://www.oardc.ohio-state.edu/weedguide/singlerecord.asp?id=810#
Ontario — http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/smooth_bedstraw.htm

Just Released — Managing Cover Crops Profitably, 3rd Edition

The New 3rd Edition of “Managing Cover Crops Profitably” was just released by the Sustainable Agriculture Network, the National Outreach Arm of USDA—SARE. The 3rd edition includes new chapters on brassicas and mustards, six new farm profiles, and a comprehensive chapter on the use of cover crops in conservation tillage systems. Updates throughout are based on more than 100 new literature citations and consultations with cover crop researchers and practitioners around the country. Appendices include seed sources and a listing of cover crop experts. The book is still priced at $19 and the full book can be viewed and ordered online at http://www.sare.org/WebStore.

Fall Harvest Management of Alfalfa after a Dry Summer — Marvin Hall, PSU Forage Specialist

During September and early October weather conditions are usually favorable for alfalfa growth. Increased emphasis on production coupled with high hay prices are causing alfalfa producers to consider harvesting during this period. When making the decision to take a fall harvest or not it is important to be understand the risks and possible economic benefit of harvesting during this period.

Importance of Fall to Alfalfa Survival: During the fall, winter hardy alfalfa plants develop cold resistance in response to shortening day lengths and cool temperatures. This process, known as hardening, involves reduced herbage production and increased carbohydrate storage in the roots. Carbohydrates are produced in green alfalfa herbage. In the spring and after cutting, carbohydrates are removed from the root until 6 to 8 inches of herbage is present, then carbohydrates begin to accumulate again. Winter survival of the alfalfa plants and spring regrowth are dependent on adequate carbohydrate storage before cold temperatures kill the herbage in the fall. About 50% of the stored carbohydrates are used during the winter for plant survival. The remaining carbohydrates are available in the spring for initial herbage growth. Cutting alfalfa in the fall may cause plants to regrow and expend some carbohydrates in the process. Subsequent regrowth often is insufficient to restore root carbohydrate levels by the first killing frost which increases the risk of alfalfa winter kill.

Alfalfa stubble left in the field has the potential to catch and hold snow which insulates the crown and roots from extremely low air temperatures. Stubble may also serve to reduce the incidence of freezing and thawing, and disrupt ice sheets which may smother alfalfa plants.

Should I Harvest Alfalfa in the Fall? Since harvesting during the hardening period disrupts carbohydrate accumulation in the roots there is increased risk of stand loss associated with fall harvesting. This lead to the traditional recommendation not to harvest alfalfa 4 to 6 weeks before the first killing frost. However, advances in alfalfa breeding and overall alfalfa management allow greater flexibility in fall harvest management than traditionally recommended. The real question is a economic gamble. Is the forage in the field worth the risk of reducing stand persistence? Alfalfa that has been drought stressed this summer has had extended periods between harvests and has had an opportunity to build up root carbohydrate reserves over a year with normal rainfall. It is still acknowledged that fall harvesting can stress the alfalfa plant and increase the potential for winter injury but management practices and planning (as outlined below) can minimize this potential.

  1. Young stands are less susceptible to winter injury due to fall harvesting than older stands.
  2. Length of harvest interval during the growing season is more important than date of fall harvest in determining alfalfa stand survival. Taking at least one harvest during the growing season at 50% bloom reduces the risk of fall harvest compared to taking all harvests at late bud or first flower.
  3. Maintaining soil fertility levels is extremely important in reducing risks associated with fall harvesting.
  4. Use of disease resistant and winter hardy alfalfa varieties will greatly decrease the risk of winter injury due to fall harvesting.
  5. Environmental conditions will moderate or aggravate the effects of fall harvesting. These include:

a. Temperatures of 5 to 15 °F will injure alfalfa crowns and roots. Fortunately, the soil and snow generally insulates the crown and root from dangerously low temperature.
b. Amount of snow cover determines the amount of crown and root protection from cold temperatures. Snow cover greater than 6 inches is usually adequate to insulate the crowns and roots from low air temperatures.
c. Soil moisture is important because water is a better conductor of heat than is air. Wet soils cool faster than dry soils which may lead to lower soil temperatures. In addition, wet soils will freeze and thaw more extensively which increases the potential for frost heaving.
d. Summer drought stress of alfalfa will reduce the risk of harvesting during the 4 to 6 week dormancy

Summary

Although fall harvesting increases the risk to long—term stand persistence compared to not fall harvesting, it should be considered a management alternative to allow flexibility in alfalfa harvest scheduling. Fall harvesting of alfalfa that has been drought stressed will cause less stand thinning than fall harvesting alfalfa that has not been drought stressed. Risks to stand persistence can be reduced through management, use of alfalfa varieties with sufficient levels of disease resistance and winter hardiness, and high levels of soil fertility (especially potassium). Practices such as leaving 6 inches of stubble in the fall or leaving unharvested strips in the field will also help by increasing the potential for snow cover.

Contributors: Dept. Crop & Soil Science: Greg Roth, Marvin Hall, Dwight Lingenfelter, and Bill Curran. Extension Educators: Kevin Fry (Armstrong County), Mark Madden (Bradford County), Don Fretts (Fayette County), Dave Messersmith (Wayne County), Mena Hautau (Berks County), Tom Murphy (Lycoming County)

Editor: Tom Murphy, Lycoming County

Upcoming Events

Real time pest and heat unit activity: http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu#

Calendar of Events: http://www.events.psu.edu/cgi-bin/cal/webevent.cgi?cmd=opencal&cal=cal209&

Readers can subscribe electronically to this newsletter at the Field Crop News Web site.

If you have problems subscribing or wish to cancel your subscription, please contact Lisa Crytser by e-mail at lac8@psu.edu or by phone at 814-865-2543.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Penn State Extension is implied.

This publication is available in alternative media upon request.

The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901, Tel 814-865-4700/V, 814-863-1150/TTY.