CMEG Crop Management Extension Group

Field Crop News

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

April 24, 2007    Vol. 07:08

IN THIS ISSUE:

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

The spell of very mild and mainly dry days is about to end. It will be replaced by rather cloudy, cooler days with mainly afternoon and early nighttime showers from Wednesday through Friday. After a chilly night with patches of frost in the hollows of northeastern Pennsylvania, Wednesday will feature lowering clouds as showers reach the western sections during the morning, the central areas about midday and the southeast before dusk. Ocean cooled air will dominate the eastern two—thirds of the Commonwealth on Thursday with low clouds, drizzle and fog. A potent line of thunderstorms will diminish as it reaches western Pennsylvania Thursday evening, but may still contain hail and high winds. The dying storms will rain themselves out in the central sections after dark. On Friday, another round of showers and a few thunderstorms will affect most of the state during the afternoon. Total rainfall for this period will range from a bit less than 0.50 inches in the southeast to more than 2 inches in the northwest. The weekend will be cool with more clouds than sun and an active breeze. A surge of very warm air in the middle of the country will likely be thwarted by a fast—moving cold front from Canada early next week. The warmer air should arrive later next week.

Timing of Burndown Herbicide Applications — Bill Curran, PSU Weed Specialist

With the cool April we experienced, many growers have not yet applied their burndown herbicide applications in no—till. Remember that environmental conditions and the size of the weeds are usually not optimal when burndown herbicides are applied, thus reducing activity and weed control. Even though the daytime temperatures are increasing, 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 additional attention. Perennials should be at least 6 to 8 inches tall and preferable more. Perennials that are beginning to flower (bud to bloom stage) are most susceptible to control with systemic herbicides. A word to the wise — Do not plant corn or soybean into live vegetation without making a burndown application or follow the planting operation ASAP with an effective knockdown herbicide program. 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:

Rye Kill Following Rye Harvested for Silage — Bill Curran, PSU Weed Specialist

Producers wishing to no—till corn into rye harvested for silage are sometimes concerned with rye regrowth. How long must you delay a burndown herbicide application after chopping rye to effectively prevent regrowth? A few years ago, we conducted a small experiment at our Rock Springs Agronomy Farm examining several herbicide treatments. The rye was chopped to about a 2–inch stubble height on May 5, while in the early head stage of development. Glyphosate was applied at 0.75 lb ae/acre (32 oz glyphosate 4L product) and Gramoxone was applied at 0.5 lb ai/acre (equivalent to 2 pt Gramoxone Inteon) to the rye stubble at three different times following harvest. Glyphosate or Gramoxone were also applied with 1.1 lb/acre atrazine 90DF. The herbicides were applied the same day (0 day), 3 days, and 7 days following rye harvest. Rye regrowth was visually evaluated in each herbicide treatment/timing and also harvested approximately 6 weeks after the burndown herbicides were applied. No crop was planted in this experiment.

No rainfall was received until about 15 days after harvest which likely impacted our results. Glyphosate alone and with atrazine effectively killed the rye regardless of timing (see following table). Apparently, an adequate amount of green leaf tissue was present at the base of the plants to absorb the systemic herbicide. The addition of atrazine did not improve or reduce control with glyphosate. For the most part, Gramoxone was less effective for control of rye than glyphosate. Gramoxone applied the day of planting and 7 days after planting was sometimes better than the 3 day after harvest treatment, probably because of subsequent plant stress that developed following the mowing. Adding atrazine to Gramoxone either improved or did not affect rye control. With more timely rainfall following the herbicide applications, the addition of atrazine should have greatly improved control with Gramoxone. Also, a higher rate of Gramoxone Inteon (3 to 4 pt/acre) should improve performance.

This study demonstrates the superior performance of a systemic herbicide (glyphosate) compared to a contact herbicide (Gramoxone) in this type of application. Delaying application following harvest may not be a concern if cutting height and the presence of healthy basal leaves at application time ensures adequate control with glyphosate.

Final Thoughts on Soybean Plant Populations — Greg Roth, PSU Grain Crop Specialist

There is considerable interest in reducing soybean seeding rates. Studies conducted here at Penn State in 2000 and 2001 at both Rock Springs and Landisville have shown no yield benefits to stands higher than 100,000 plants per acre. Trials at both Rock Springs and Landisville this year supported similar conclusions.

At our Rock Springs location, we planted 15 inch row soybeans no—till in corn stalks. We targeted 75, 100, 125, and 150 thousand plants per acre. We assumed an 85% emergence rate, but actually achieved a 76% emergence which resulted in populations of 67, 87, 114, 134 thousand resulting in soybean yields of 53, 55, 59, and 58 bushels per acre. In this trial, yields dropped a few bushels when populations dropped under 100 thousand plants per acre. At a seed cost of $35/bag and $7.00 soybeans, the highest returns occurred with the 145 thousand seeding rate.

Iowa State, for example, now recommends 125,000 under ideal conditions to 140,000 seeds per acre to achieve a final stand of at least 100,000 plants per acre. As evidenced by our trials, there is probably some opportunity to reduce seeding rates in our environments with good conditions and management. I am a little more comfortable with recommendations in the 140,000 to 150,000 per acre range in well managed environments here.

Good management involves achieving good seed to soil contact, reasonable seed depth uniformity, good quality seed, and control of seed pathogen and insect pests if they are present. Also, monitoring stands and determining the emergence rates of soybeans is another key management practice. In our trials last year, we found much of the loss in stand occurs early in the season. Emergence rates of 65 to 80% were common, but fell to 35 to 40% for two fields.

Take time this spring and monitor soybean stands and estimate emergence rates in the fields you work with, and then make population adjustments based on that in the future. Theoretically, you can estimate the seeding rate you'll need by dividing the desired final stand by the average emergence rate (i.e., 100,000/0.72 = 139,000). In practice, sometimes adding another 5–10% for insurance purposes might be appropriate, especially where stressful situations are anticipated.

Nitrogen Tests—Know Before You Grow—Jeffrey Graybill, CCA, Lancaster Co. Extension and Doug Beegle, PSU Soil Fertility Specialist

The Pre—Sidedress Nitrogen Test or Chlorophyll Meter were developed to help make decisions about nitrogen fertilizing when the amount of nitrogen available from present or past manure applications or other organic nitrogen sources is uncertain. If manure applications in the past have been somewhat regular, significant amounts of nitrogen will become available as the season progresses. In these cases you can use these tests and take a “wait and see” approach and avoid application of unnecessary fertilizer.

The PSNT (a soil nitrogen test) and Leaf Chlorophyll Meter both can be used when corn is approximately 8-12“ to test and see if you need any additional N. The only limiting factor is that they are the most reliable if you do not apply broadcast N before planting. Applying starter is okay, but if you plan to use the Chlorophyll Meter test do not apply more than 15 lb N/A in the starter. You can then come back, test, and determine if additional N is needed. This would then be applied as a sidedress treatment which is the most efficient use of expensive nitrogen. Many county Extension and Conservation District offices now have chlorophyll meters or will assist you in taking a soil nitrate (PSNT) test. Check with your local office.

Nitrogen Fertilizer Through the Planter — Doug Beegle, PSU Soil Fertility Specialist and Jeffrey Graybill, CCA, Lancaster Co. Extension

In some fields soil test levels of phosphorus are so high that use of phosphorus in starters may have no benefit and in some cases be prohibited by nutrient management regulations. In cases like this research has shown that nitrogen alone such as ammonium sulfate as a starter is just as beneficial if the amount used close to or in the row is within recommended amounts. Don’t apply more than 70 lb N+K2O within 2 inches of the seed and be careful especially if the fertilizer contains urea N. If you are trying to put even more nitrogen on through the planter to add to the total nitrogen recommendation, how much can you safely put on? We know from research trials that moving the placement of nitrogen 6 inches from the row allows you to go just about as high as you need to. But this removes the starter effect. If you have another separate applicator system you can maintain a starter effect by putting a small amount of pop—up starter on the seed and then the rest of the N solution or dry product off of the row through the fertilizer openers. Liquids can also be dribbled on the surface between the rows.

Job Announcement — York County Soil & Nutrient Management Educator

Penn State Cooperative Extension is accepting applications for an individual to provide programming in the broad areas of nutrient management education, soil quality and soil health, basic physical and chemical properties of soils, and agronomic application of organic residuals. A master’s degree is required with preference given to degrees in agronomy, soil science or related field and eligibility to be a certified crop advisor. Deadline for applying is May 11, 2007. Visit PSU website http://psu.jobs under Cooperative Extension for details. For an application, email (bss1@psu.edu) or call (814) 863-3452. Penn State is committed to affirmative action, equal opportunity and the diversity of its workforce

Upcoming Events:

Cover Crop Research and Management Summit
June 5, 2007
Tuesday, 9:30am–3:30pm
Penn State Rock Springs Agronomy Farm, Centre Co.
Cost: $10
Lunch and handouts will be provided

During this cover crop management field day, you will have an opportunity to see and hear about the latest cover crop research at Penn State as well as observe first hand some of the tools and practices being tested. Topics will include choosing cover crops based on farming goals, how to grow or capture nutrients and the importance of carbon and nitrogen, improving soil quality, controlling cover crops including using rollers/crimpers and how cover crops can help control weeds.

This tour will be given by a distinguished group of Penn State researchers from across the college who have cutting edge projects underway focused on cover crops. In addition, Rodale Institute staff will be on hand to share their management experience in organic farming systems. Certified Crop Advisor CEU's will be available at this event.

You must pre register with Lisa Crytser at Penn State to ensure you have a spot at lunch and on the wagons. Please pre—register by May 30, 2007 by phone (814–865–2543) or email (lac8@psu.edu).

American Forage and Grassland Conference
June 24–26 in State College
For more information check out http://www.afgc.org/mc/page.do?sitePageId=42837&orgId=afgc

Agronomic Weed Management Research Tour at Penn State
July 10, 2007
Tuesday, 9:00–12:00 noon
Penn State Rock Springs Agronomy Farm, Centre Co.
Cost: $15
Lunch and handouts will be provided

A number of experiments will be showcased and available for viewing including many of the new corn and soybean herbicide programs plus the latest information on herbicide resistance, cover cropping and weed management research. Certified Crop Advisor CEU’s will be available at this event.

You must pre register with Lisa Crytser at Penn State to ensure you have a spot at lunch and on the wagons. Please pre—register by July 3, 2007 by phone (814–865–2543) or email (lac8@psu.edu).

Penn State Agronomic Field Diagnostic Clinic
July 24 and 25
Penn State Rock Springs Agronomy Farm, Centre Co.

The dates and topics for our annual Diagnostic Clinic have been set. As in the past, the Clinic is a one—day event conducted at the Penn State Agronomy Research Farm near Rock Springs, PA. This year’s Clinic will be held on Tuesday, July 24 and then repeated on Wednesday, July 25, 2007. The topics include cover crop selection and management, no—till planter adjustments and attachments for use in cover crops, an overview of biomass crops for alternative energy use, nitrogen management issues, and pest management topics. As always, various credits will be offered.

Registration forms will be mailed and posted on our CMEG website (http://cmeg.psu.edu/) as time gets closer, so you can register and get additional information on each of the topics.

For additional information or comments about the Diagnostic Clinic contact Dwight Lingenfelter at (814) 865–2242 or by email, DwightL@psu.edu

Ag Progress Days — August 14–16

Contributors: Dept. Crop & Soil Science: Bill Curran, Marvin Hall, Greg Roth, Sjoerd Duiker, Doug Beegle, Paul Knight. Extension Educators: Mena Hautau (Berks), Kevin Fry (Armstrong), Andrew Frankenfield (Montgomery), Tom Murphy (Lycoming), Susan Alexander (Jefferson), Jeff Graybill (Lancaster)

Editor:John Rowehl

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&

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