CMEG Crop Management Extension Group

Field Crop News

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

April 22, 2008    Vol. 08:07

IN THIS ISSUE:

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

A blocking pattern will continue to dominate the region as warm and generally rain—free conditions effect the state. A weakening cool front will cross Pennsylvania on Wednesday with thundershowers scattered over less than half the area during the late afternoon and evening. Dry and very mild weather will return on Thursday and most of Friday until more humid air returns late in the day accompanied by scattered thunderstorms. Another cool front is expected later Saturday with showers in most sections (about 90% of the state). It will remain milder than normal on Sunday and turn even warmer on Monday. A sharp cold will approach the region later Monday or Tuesday. About a third of the computer forecasts indicate that this front will stall nearby and be followed by several cool, cloudy and damp days at end of April and beginning of May. Indications point to another very mild period during the first third of May with a possible cold snap (and scattered frost) during the middle third of May (10–20). Odds favor a wet June with well above average rainfall and near normal temperatures.

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

Scout Now for Alfalfa Weevil — Delbert Voight, Lebanon County Educator

Del Voight suggests using a sweep net to scout for alfalfa weevil now, but go here to read more about how to determine economic thresholds. With the high price of hay, thresholds need to be reviewed.

http://lebanon.extension.psu.edu/Agriculture/FarmMgt/Alfalfa.htm

Thoughts About Burndown Herbicide Applications — Bill Curran, PSU Weed Specialist

The first half of April was cool, but in the last week the daytime temperatures have really started to warm up. I have observed many winter annual weeds such as common chickweed, henbit, and deadnettle in our no—till fields that are now flowering. Common ragweed and lambsquarters are emerging with the foxtails and velvetleaf not far behind. It’s a good time to remember that environmental conditions and the size of the weeds greatly affect the activity of burndown herbicides and weed control. Even though the daytime temperatures have increased, nights can still be cool, which impacts active weed growth and herbicide uptake and activity. Also, larger annual weeds and perennials that have overwintered tend to be more difficult to control under cold conditions. There is often a tradeoff in getting good control of the winter annual weed populations like chickweed and deadnettle (where smaller is better) and trying to suppress perennials like Canada thistle and quackgrass (where bigger is better). It’s difficult to do a good job controlling both of these types of weeds with a single application.

In general, herbicides such as glyphosate and 2,4–D provides the best control when annual weeds are 6 inches tall or less and still in the vegetative stage of growth. Winter annuals that are flowering may require higher rates or different combinations of products. Perennials should be at least 6 to 8 inches tall and preferable more when a systemic herbicide is applied. Perennials that are beginning to flower (bud to bloom stage) are most susceptible to control with systemic herbicides.

Remember — do not plant corn or soybean into live green vegetation without making a burndown application or follow the planting operation ASAP with an effective knockdown herbicide program. Corn in particular is very susceptible to early season competition for light, nutrients, and water. Planting into green vegetation is challenging for any crop seed and can lead to additional problems such as hair pinning, open slits, poor seed to soil contact, insect and bird problems, etc. which all result in reduced stands.

Here are a few additional suggestions to help improve burndown herbicide activity:

Cover Crop Termination — Sjoerd Duiker, PSU Soil Management Specialist

As we gain more experience with cover crops, our thoughts are evolving about their management. I was looking back at a few articles I wrote in the past years and noticed an emphasis on early burndown. However, after my trip to Latin America and taking another look at diverse experiences with cover crops over the past years, I am starting to lean more towards considering a later burndown. Here is why:

  1. Organic matter content. According to a USDA review we need to return some 4,500 lbs/A of above—ground dry matter per year to maintain soil organic matter content. Our cover crops help us reach this goal, but we should let them accumulate as much growth as possible to reach it. In a rye cover crop study Bill Curran and I did at Rock Springs a few years ago we accumulated 1,000–1,500 lbs/A dry matter with early—May burndown, while we achieved 1,700–6,000 lbs/A by killing it 10–14 days later. Burning our cover crops down a bit later helps us reach our dry matter goal.
  2. Mulch cover. The mulch cover is what makes no—till tick. It provides the protection from erosion, reduces water evaporation during the summer, and provides food for soil organisms (most well—known being the night-crawler).
  3. Nutrient uptake and recycling. Nutrient uptake and recycling is related to the biomass we allow the cover crops to accumulate. It is safe to say that a cover crop of 2,000 lbs took up twice as much N, P and K as a cover crop of 1,000 lbs. These nutrients will be made slowly available to the next crop as the cover crop decomposes during the next year.
  4. Nitrogen fixation. I am getting a bit of experience under my belt with nitrogen—fixing cover crops. The nitrogen content of the legumes is about 4% for hairy vetch, and about 3% for crimson and red clover. The more biomass these legumes accumulate, the more N we can expect from them for the next crop. In the case of hairy vetch, most of the nitrogen in the above—ground biomass can be counted on for the following summer crop. In the case of the clovers it may be spread out over two years because of the slower decomposition of the residue.
  5. Weed control. Cover crops can help control weeds. One of my grad students recorded a significant reduction in weed growth after a rye cover crop that was rolled down in May to the point that no post—emergence herbicide application was needed this past year. We still have to refine our recommendations based on more years of data, but it stands without question that heavy cover crops suppress weeds more than thin stands of cover crops.

So before you make the decision to burn the cover crop down, take a look at what there is in the field. If there is little biomass, perhaps you should consider waiting a bit before you terminate your cover crop.

Think About Lambsquarters Management Now — Bill Curran, PSU Weed Specialist

Common lambsquarters is one of the most common and problematic weeds that we deal with in Pennsylvania. Triazine—resistant lambsquarters is widespread in the Northeast and ALS—resistant biotypes have been identified in Ohio and Michigan. Lambsquarters that are more tolerant to glyphosate have become more common in a number of states including Pennsylvania in response to the repeated use of glyphosate in Roundup Ready crops.

There are a number of effective soil—applied and POST products for lambsquarters control in corn, but the story is different for soybeans. Although, there are a number of effective PRE soybean herbicides for lambsquarters control, there are only a few effective POST products. For a more complete discussion on lambsquarters biology and control, see the Glyphosate Stewardship Series publication titled Biology and Management of Common Lambsquarters at http://glyphosateweedscrops.org/Info/GWC-11.pdf

Here are some “slightly modified” key points that our colleagues at Ohio State and Purdue suggest for controlling lambsquarters in soybeans and corn.

Assessing Corn and Soybean Stands — Del Voight, Lebanon County Educator

Go to this site to read more about assessing corn and soybean stands. The article includes a summary table of evaluating planting date and yield reduction with later planting dates.

http://fcn.agronomy.psu.edu/2008/assessing_corn_and_soybean_stands.pdf

How Does the Cover Crop Roller/Crimper Handle Standing Corn Stalks? — Ron Hoover, Department of Crop and Soil Sciences

A large roller/crimper is being tested for its ability to roll down heavy cover crops to create a substantial layer of surface mulch into which corn or soybean can be planted or drilled. Several versions of this tool have been developed where a 12 to 16 inch diameter well casing serves as a rotor onto which crimping blades are attached around the rotor in a chevron wrapping pattern. Common widths of rotors are 3, 4, 6, 8, 10.5 and 15 feet. I and J Manufacturing in Lancaster County will build to the above sizes, or to a custom width if desired. Several researchers at Penn State are beginning their fourth year of trials with two different 10.5 feet—wide rollers. Rollers can be front or rear mounted on tractors. Results of trials where cover crops that are sprayed with reduced rates of burndown herbicide are then rolled and directly planted into have been very successful. Rolling/crimping without herbicide has produced less consistent results and it is in these conditions that most current work is focused.

Numerous acres of corn stalks are flail—chopped or gyro—mowed each fall and winter following grain harvest. The reasons for chopping are varied. The most frequently cited reasons include: reduce stalks that can interfere with the planting of the next crop or harvest of soybeans, reduce future pest problems by exposing insect pests and pathogens to harsh winter conditions, and get stalks on the ground to better protect soil and accelerate stalk decomposition. Implements that accomplish this are typically tractor PTO—driven, requiring a lot of fuel to operate, are somewhat expensive to purchase, require regular maintenance, and consume replacement parts that are not cheap. Roller/crimpers similar to that being tested at Penn State are modestly priced, can be arranged into gangs similar to the large multi—gang reel mowers used on lawns, can be used at field speeds comparable to those of disk mowers, and have very few moving parts to service. I front mounted one of the 10.5 foot wide rollers and went into standing corn stover to see how effective the tool might be in putting down corn stalks.

Rolling stalks on a frosty early April morning produced less than desired results. While stalk heights varied from 18 to 30 inches, a single roller pass resulted in no stalks remaining truly vertical. However, few were left in the optimal “flat” position on the ground. The tractor tires helped in this regard. Although the test wasn’t a success, it was not a complete failure. It provided some insight into what field conditions may improve the results. I suspect that under different conditions, more stalks could be put down and kept down by rolling. Because some root balls were rolled over and many stalks were bent but not “cracked”, timing the operation to occur while stalks and the soil surface are frozen should help hold corn roots in place while breaking over more stalks. The results may be optimized under conditions of wet soil and, especially, wet stalks that follow a few days of showers which are followed soon after by several days in the “deep freeze”. With this scenario, I would anticipate a frozen field that resists tractor damage and corn stalks made more brittle due to increased internal moisture that more readily break over at or near the root. We plan to investigate this further with the roller/crimper and probably with one of the heavy cultipackers that can still be found on many Northeast farms.

USDA Weekly Crop Progress Reports — Joel Hunter, Crawford County Educator

USDA Crop Progress Reports are updated each Monday. To view go to:

http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1048
or
http://www.usda.gov/nass/pubs/staterpt.htm

Soybean Yield Contest Information Now On—Line

Go to this site to obtain the entry brochure. Deadline is August 31, 2008. http://www.pasoybean.org/YieldContest/yieldcontest2008.pdf

Contributors: County Educators: Paul Craig (Dauphin), Andrew Frankenfield (Montgomery), Joel Hunter (Crawford), Mark Madden (Sullivan), David Messersmith (Wayne), Grant Troop (Lebanon), Delbert Voight (Lebanon). Department of Crop and Soil Sciences, Douglas Beegle, William Curran, Sjoerd Duiker, Marvin Hall, Dwight Lingenfelter, Ronald Hoover.

Editor:Mena Hautau (Berks)

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