CMEG Crop Management Extension Group

Field Crop News

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

August 1, 2006    Vol. 06:14

IN THIS ISSUE:

Weather Outlook — Paul Knight

The crest of the heat wave will be on Wednesday with record maxima in many sections and most places from the Susquehanna to the Delaware Valley topping 100F. An odd thunderstorm will erupt over the Laurel Highlands late in the day. Thursday will stay hot and humid, but there will be thunderstorms in about 50% of the area. A cold front will cross the state on Friday with the focus of thunderstorms mainly from the central mountains eastward. Storms on Thursday evening and Friday could be severe with damaging winds possible. It will turn less humid in the western counties on Friday, but much of the day will stay uncomfortably warm and humid in the east. Relief will arrive for the weekend with much lower humidity and temperatures staying above seasonal levels, but more comfortable than the mid—week. The humid air will return later Sunday and Monday. Scattered thunderstorms are expected on Monday as a new cool front pushes slowly into the region. Tuesday is expected to be warm and humid with scattered storms in the southern sections.

Assessing Corn Pollination and Making Mid—Season Yield Estimates — Greg Roth, Grain Crop Management and Dave Messersmith, Wayne Co.

Pollination of the corn crop has recently completed in many areas of the state. You can determine how successful pollination was by gently pulling the husks off of an ear once the silks have turned brown and then gently shaking the ear. Those silks that remain attached to the ear were not pollinated. Often these will be the late emerging silks from the ear tip but they can be scattered throughout the ear.

Once the pollination process is complete, a rough grain yield estimate can be made by determining the average number of kernels per ear and multiplying it by the plant population. Multiply the number of rows by the number of kernels per row to get the number of kernels per ear. Then multiply this number by the plant population to get the kernels/acre. Divide the kernels/acre by 90,000 to get the yield estimate in bushels/acre.

Example: 18 rows x 30 kernels/row x 25000 plants/acre = 13.50 million kernels/acre

13.5 million/90,000 = 150 bushels/acre

Insect Damage on Soybeans — John Rowehl, Cumberland Co.

Insects posing the greatest potential damage to soybean crops are defoliators. Feeding activity has been going on for several weeks. However as soybeans are forming and filling pods, there is reason to keep an eye on the amount of damage going on.

Common defoliating insects are Mexican bean beetle, green clover worm, grasshoppers, bean leaf beetles and Japanese beetles. Green cloverworms usually are controlled by a fungal disease. High humidity with warm temperature, favorable for the development of the fungus, may be sufficient to reduce a high population of green cloverworms. Japanese beetles (were brought accidentally to New Jersey from the Orient in 1916), have none of their natural predators or diseases around to keep them in check.

Soybean plants can tolerate up to 35 percent defoliation prior to bloom; about 20 percent while pods are small and soft; and about 35 percent when the seeds are filling. Defoliation below these levels has not adversely affected yields.

However, defoliation is not the end of the story. The bean leaf beetle also feeds on soybean pods. This feeding scars the pods and can open up entry to disease that can lead to shrunken, discolored or moldy seeds. As the number of pods fed on increases, the risk of injury to the developing soybean seeds also increases.

Here are links to a couple of fact sheets from Ohio and Missouri that cover this extensively.

http://ohioline.osu.edu/icm-fact/fc-23.html

http://outreach.missouri.edu/explore/agguides/pests/g07150.html

If you determine a rescue treatment for insects is needed you can find a list of products for the various pests in the Penn State Agronomy Guide.

Evaluate Soybean Nodulation — Kevin Fry, Armstrong Co.

While scouting your soybean fields for escaped weeds, insects and diseases, don't forget to take a look at the nodules. The ample rainfall this growing season allows for easy scouting of the soybean root system. Pull out a few plants and examine the root system. The tap root should be strong, thick and rather long (12 in.) with a number of large secondary roots. Along the tap root, you should be able to find large numerous nodules that when cut open show a red or pink interior. The color develops from a reaction of oxygen with the compound leghemoglobin found in nodules that helps maintain reducing conditions (low oxygen levels) inside the nodule so the Bradyrhizobia can function. Non-functioning nodules can have white, green, or even black interiors as the nodule decays.

There have been numerous advances in inoculants in recent years. Inoculant manufacturers have focused their research and development efforts on finding ways to improve inoculants. Combining strains of Bradyrhizobium japonicum that are most productive in different environments results in products that are productive over a wider range of environments. Combining organisms that offer plant growth promotion hormones or disease control in conjunction with regular rhizobials is another new development. Other areas of interest are the biological signals that induce nodulation. The addition of “extenders” to inoculation materials allows the materials to be applied to seed up to thirty days or more before planting without loss of productivity if the seed is stored properly. One new material will allow application up to 60 days before planting even when applied in combination with selected fungicides which allows for seed inoculation at the warehouse instead of the farm. Go to the following for links to soybean inoculant companies. http://corn.osu.edu/agcrops/resources/InoculantSources.php

The traditional recommendation for inoculants was to use it if the field hasn't been in soybeans for 3—5 years. Recent studies have shown a yield response to inoculant use in fields with a corn and soybean rotation.

The average yield increase from 64 Ohio trials is 1.94 bu/ac and has produced a profit of about 300 percent when beans were worth $6.00 per bushel and when the inoculation material costs $3.00 per acre. For most inoculation products, a one half bushel per acre yield increase is profitable. Yield increases of two to seven bushel per acre have been common in productive producer fields where the seed was inoculated properly and planted into moist soil and in a timely manner.

Iowa State also had similar results in 2005, their results can be seen at http://extension.agron.iastate.edu/soybean/production_seedinoc.html

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 1/4 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.

Ag Progress Days — Mark Madden, Sullivan County

A full slate of activities and opportunities to learn are scheduled for this annual event at the Russell E. Larson Agricultural Research Center on August 15—17th. Fresh reorganization locates the Conservation Education program adjacent to the Crop & Soils Tent to capitalize on the close relationship between these attractions and to offer convenient access to interested farmers.

Live demonstrations of the latest and best in production technology will be showcased along with specialized cover—crop rolling and manure—application research equipment. Times and locations of all demonstrations will be announced http://apd.cas.psu.edu/. Specialists from Penn State and the Pennsylvania Crop Management Association will answer your crop—production questions and farmer—members as well as associates of the Pennsylvania No—Till Alliance will discuss no—till crop—production strategies.

The Pennsylvania Hay Show sponsored by the Pennsylvania Forage and Grasslands Council is held each year in the Crop & Soils Tent. Hay producers are encouraged to enter their finest samples and in return can expect to receive a feed quality analysis of the forage. Applications are available from most Cooperative Extension offices.

Contributors: State Specialists: Sjoerd Duiker, Greg Roth Extension Agents: Kevin Fry (Armstrong), Jere Wingert (Franklin), Jeff Graybill (Lancaster), Dave Messersmith (Wayne), John Rowehl (Cumberland), Dwane Miller (Schuylkill) and Mark Madden (Sullivan)

Editor:Mark Madden

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&

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