|
http://www.ag.ohio-state.edu/~corn/ |
|
September 9 - September 15, 2002
C.O.R.N. 2002-30
In This Issue:
A) Planting Wheat For Improved Yields
B) Assessing The Risk Of Frost Injury To Corn
C) Controlling Warm-Season Perennials In Wheat Stubble
D) How Was Marestail (Horseweed) Control This Season??
E) Precision Agriculture Highlighted At Farm Science Review
F) Osu Field Guide Available At Farm Science Review
Shooting for ultra high yields by using extra inputs is not profitable for most Ohio wheat producers. That is because the weather and climate of Ohio is usually not ideal for high yield wheat production. Most years, our weather is too wet in the spring resulting in serious disease and loss of yield. June is usually too hot and kills our crop well before it has time to reach its maximum yield potential. When we have one of those rare dry springs and little disease followed by a cool June, the yields of some fields have hit 120 bu/ac or more. Because those good growing seasons are very rare, we should manage for the more normal weather which usually prevents us from taking advantage of high management inputs such as high seeding rates, and extra nitrogen.
The more prudent production system is one of defensive management: planting after the fly-safe date to dodge diseases; holding seeding and nitrogen rates down to reduce disease and lower the cost of production; using resistant varieties instead of applying fungicides, etc. This management system will not produce the maximum possible yield in those really good years, but it will be the most profitable system for all those other years (the norm) when the weather is not ideal for high yields. An important point to keep in mind is that "the most profitable amount of any input is always less than the amount needed to produce the highest yield."
Select wheat varieties with high yield potential, high test weight, good winter hardiness and good standability. Always select varieties with resistance to the diseases prevalent in your area of the state. Plant more then one variety each year to reduce the risk of disease losses and to spread out harvest. Select varieties with resistance to wheat spindle streak mosaic, powdery mildew and leaf rust. Varieties with moderate resistance to Stagonospora glume blotch and Fusarium head scab are also available.
Information on wheat variety performance can be obtained in the annual "Ohio Wheat Performance Trial" OSU Horticulture and Crop Science Department Series 228 available at the County Extension office or on the internet at http://www.ag.ohio-state.edu/~perf/
Plant wheat immediately after the Hessian Fly Safe date. Planting within the first 10 days after this date ensures the proper planting time to avoid serious insect and disease problems including Hessian Fly, Barley yellow dwarf virus and several foliar diseases. Early planting (before the Fly safe date) has reduced yield by 7.5 to 20% in research trials due to increased disease levels as compared to those planted after the Hessian Fly Safe Date.
The optimum seeding rates for Ohio are between 1.2 and 1.6 million seeds per acre or 16 to 21 seed per foot of 7.5-inch row. High seeding rates (above 30 seeds per foot of row) increase lodging potential, costs more money, but does not increase yield. Plant seeds 1 to 1.5 inches deep uniformly across the field . This planting depth is critical to winter survival and tiller development. Before planting, apply 20 to 30 pounds of nitrogen to increase fall growth, improve winter hardiness and increase yield. Wheat also requires at least 45 parts per million of available phosphorus per acre in the soil to produce really good grain yields. If a soil test indicates less than 40 parts per million, then apply 80 to 100 pounds of P2O5 at planting. Soil potassium should be maintained at levels of 135, 165, and 185 parts per million for soils with cation exchange capacities of 10, 20 or 30, respectively. If potassium levels are low, apply 60 to 100 pounds of K2O at planting. In Ohio, limed soils usually have adequate calcium, magnesium and sulfur for wheat. Soil pH should be between 6.5 and 7.0.
For the latest information on profitable wheat production, plan to attend the annual meeting of the Ohio Wheat Producers on January 29, 2003 at the American Legion Post in Pemberville, Ohio in Wood County.
Physiological maturity (when kernels have obtained maximum dry weight and black layer has formed) occurs 7 to 8 weeks after silking. At physiological maturity (kernel moisture approximately 30-35%), frosts have little or no effect on the yield potential of the corn crop.
Table 1 shows the average number of calendar days and growing degree days (GDD) required to reach physiological maturity after silking. With average daily high and low temperatures of 80 and 60 degrees F, 20 GDD accumulate each day. At these temperatures, 65 days from silking to maturity are required (1300 divided by 20). Therefore, corn silking in early August would probably not be safe from major yield reductions due to frost until early October.
With "cooler" high and low temperatures of 75 and 55 degrees, only 15 GDD accumulate daily, requiring more than 87 days from early August silking to maturity. This would require warm, frost-free weather until mid October, which is past the average frost date for much of the state.
Table 1. Relationship Between Kernel Growth Stage and Development. Source: National Corn Handbook. Chapter 40. Growing Season Characteristics and Requirements in the Corn Belt. R.E. Nield and J.E. Newman, 1986.
How many GDD can be expected from now until an average date of a killing frost? To answer this question, estimate the expected GDD accumulation from September 9 until the average frost date (50% probability) for different regions of the state (Table 2). These GDD expectations are based on 30-year historical normals reported by the Ohio Agricultural Statistics Service. The growing degree day accumulation was calculated using the 86/50 cutoff, base 50 method.
If you want to determine the "youngest stage of corn development"
that can safely reach black layer before the average frost date at a given weather
station, use the information in Table 2 on remaining GDD in conjunction with
Table 1 which indicates GDD requirement to reach black layer at various stages
of grain fill. Compare "GDD remaining" for the site with the GDD required
to achieve black layer depending on the corn's developmental stage.
If your corn is in the late milk/early dough stage as of Sept. 9, will it be safe from frost? Probably not, because it needs about 775 GDD to reach black layer based on the kernel development - GDD accumulation relationships indicated in Table 1. Table 2 indicates that there is no region of the state with that number of GDDs remaining until the 50% frost date.
If your corn is in the fully dented stage as of Sept. 9 will it be safe from frost? Table 1 indicates that it needs about 250 GDD to reach black layer from full dent stage and Table 2 indicates that most regions of the state will accumulate sufficient GDD to escape frost injury. The exceptionally warm temperatures we've experienced recently are helping with heat unit accumulation. Moreover, late planted corn has shown the ability to adjust its maturity requirements. Corn planted in early June compared to early May requires 200 to 300 fewer GDDs to achieve physiological maturity.
Regions in which corn is at greatest risk to frost damage are those with late September/early October frost dates, especially sites in northeast and east central Ohio.
It is now time to consider spraying warm-season perennials, such as johnsongrass, hemp dogbane, common milkweed, the bindweeds, common pokeweed, and others that emerge late in the spring. These species will soon begin to send nutrients down to the roots or rhizomes that make them perennial. When this occurs, glyphosate will travel with the nutrients and kill most of the roots and rhizomes along with the above-ground part of the plant. The middle of September to the end of September is usually the time to make this application. With the current drought conditions, delaying applications until a rainfall would be ideal, however, if temperatures change suddenly into the high 30's the warm-season perennials may not be adequately controlled. One way to help overcome the current drought stress, would be to add an additional 0.5 to 1.0 pint/A of glyphosate to the intended rate. Increasing the rate may not work in all cases, but should be helpful.
For johnsongrass, consider at least 0.75 pounds acid equivalent/A (22 to 32 oz/A depending upon formulation used) of glyphosate. For the other species mentioned above use at least 1.2 pounds acid equivalent/A (33 to 48 oz/A depending upon formulation used) of glyphosate plus 1.0 pint/A of 2,4-D ester. Higher rates of glyphosate and/or 2,4-D should provide more effective control.
Now is not the time to control cold-season perennials such as dandelion, Canada thistle, quackgrass, curly dock, and others. Nor is it a good time to control biennials, such as wild carrot and poison hemlock, or winter annuals. These weeds should not be sprayed until mid-October to late October during Indian Summer.
We are interested in hearing how well marestail (horseweed) was controlled this season in soybeans. Were there any problems with marestail control in Roudup Ready soybeans? Western Tennessee now has 400,000 acres infested with glyphosate-resistant marestail. If you have any comments feel free to contact Jeff Stachler at stachler.1@osu.edu or 614-292-1393 or Mark Loux at loux.1@osu.edu or 614-292-9081.
We would also be interested in hearing about weed control with ALS-herbicides as it pertains to species that have not yet been confirmed resistant.
The Precision Agriculture Team within OSU Extension is sponsoring a precision agriculture field demonstration in the afternoon during each day of Farm Science Review, September 17-19. The field demonstration will run from 1:00 to 4:00 Tuesday (Sept. 17) & Wednesday (Sept. 18), and 1:00 to 3:30 on Thursday (Sept. 19). We will have one of the largest demonstrations and displays of GPS-based vehicle guidance systems in the country. There will be nine different driving aids (lightbar guidance systems) and four auto-steering tractors.
Farm Science Review visitors will be able to drive the utility vehicles with the lightbar guidance systems and see the auto-steering systems up close. The first GPS-based auto-steering combine ever to be released for commercial operation in the United States will be shown in the soybean harvest demonstration. The application of hand-held computers and GPS receivers will be demonstrated for use in agriculture. Along with the field demonstrations, there will be a tent in Alumni Park (Friday Ave.) featuring other precision agriculture activities at OSU such as new sensor technologies, remote sensing and a yield monitor simulator. We invite you to see our precision agriculture activities during Farm Science Review. Come see the future of agriculture!
For more information please contact Matthew Sullivan, Extension Program Specialist in Precision Agriculture, at 614-247-6286 or at sullivan.64@osu.edu by email.
Readers can subscribe electronically to this newsletter by sending an e-mail message to: corn-out-on@postoffice.ag.ohio-state.edu. A successful subscription message will receive by an automatic reply from the listserv. Contact your local Ohio State University Extension Office or e-mail labarge.1@osu.edu if you have problems subscribing.
Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/
C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.
State Specialists: Pat Lipps, Anne Dorrance & Dennis Mills (Plant Pathology), Peter Thomison (Corn Production), Jim Beuerlein (Soybeans and Small Grain Production Specialist), Jeff Stachler (Weed Science), Matthew Sullivan (Precision Agriculture), and Bruce Eisley (IPM) Extension Agents: Jim Lopshire (Paulding), Andy Kleinschmidt (Van Wert), Ray Wells (Ross), Clark Hutson (Seneca), Steve Foster (Darke), Howard Siegrist (Licking), Harold Watters (Miami), Glen Arnold (Putnam), Roger Bender (Shelby), Barry Ward (Champaign), Greg La Barge (Fulton)Editor: Andy Kleinschmidt Web Editor: Tom Rosati
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868
| C.O.R.N. | Newsletter | Archive | Search | Questions? | Ohioline | Publications |