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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2004-30

Dates Covered: 
September 7, 2004 - September 14, 2004
Andy Kleinschmidt

Wheat Planting: Doing it Right!

Authors: Jim Beuerlein, Patrick Lipps, Edwin Lentz

High yields and low cost of production are necessary for wheat to be a viable economic partner in Ohio. Nearly every farm in Ohio has a field or two that could benefit from planting wheat, if for no other reason than to help reduce problems associated with continuous planting of soybeans and corn. The most prudent wheat production system is one of defensive management. Consistent high yields can be obtained by following a few important management guidelines. Below are listed the most important management decisions that Ohio wheat producers need to make at fall planting time to produce a crop with satisfactory economic returns.

1) Select high-yielding varieties with high test weight, good straw strength and adequate disease resistance. Do not jeopardize your investment by planting anything but the best yielding varieties that also have resistance to powdery mildew and Stagonospora leaf blotch. Avoid varieties with susceptibility to Fusarium head scab. Plant seed that has been properly cleaned and treated with a fungicide seed treatment to control seed borne diseases.

2) Plant after the Hessian Fly Safe date for your county. This date varies beginning on September 22 for northern counties to October 5 for the southern most counties. 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. Planting before this date has lowered yield by 7 to 20% in research trials due to diseases and insect problems.

3) Optimum seeding rates are between 1.2 and 1.6 million seed per acre. For drills with 7.5 inch row spacing this is about 18 to 24 seed per foot of row. When wheat is planted on time, actual seeding rate has little effect on yield, but high seeding rates (above 30 seeds per foot of row) increase lodging. There is no evidence that more seed is better, it only costs more money.

4) Planting depth is critical for tiller development and winter survival. Plant seed 1.5 inches deep and make sure the seeding depth is uniform across the field. No-till wheat into soybean stubble is ideal, but make sure the soybean residue is uniformly spread over the surface of the ground. Shallow planting is the main cause of poor over-winter survival due to heaving and freezing injury. Remember you can not compensate for a poor planting job by planting more seeds; it just costs you more money.

5) Apply 20 to 30 lb of actual nitrogen per acre at planting to promote fall tiller development. Wheat also requires at least 45 ppm of available phosphorus per acre in the soil to produce really good grain yields. If the soil test indicates less than 40 ppm, then apply 80 to 100 pounds of P2O5 at planting. Soil potassium should be maintained at levels of 135, 165 and 185 ppm 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.

The key to a successful wheat crop is adequate and timely management. The above recommendations are guidelines that may be fine-tuned by you to fit your farming operation and soils. You can review more details on these, and other, research-based wheat management recommendations on-line at

Corn Drydown

Authors: Peter Thomison

Many agronomists recommend to begin harvesting corn for dry grain storage at about 24 to 25% grain moisture. Allowing corn to field dry below 20% risks yield losses from stalk lodging, ear rots, and insect feeding damage. Localized root lodging caused by heavy rain and strong winds earlier this year may also slow harvest and contribute to yield losses.

The loss of one "normal" sized ear per 100 feet of row translates into a loss of more than one bushel/acre. In fact, an average harvest loss of 2 kernels per square foot is about 1 bu/acre! According to an OSU ag engineering study, most harvest losses occur at the gathering unit with 80% of the machine loss caused by corn never getting into the combine.

Corn will normally dry approximately 3/4 to 1% per day during favorable drying weather (sunny and breezy) during the early warmer part of the harvest season from mid September through late September. By early to mid October, drydown rates will usually drop to 1/2 to 3/4% per day. By late October to early November, field dry down rates will usually drop to 1/4 to 1/2% per day and by mid November, probably 0 to 1/4% per day. By late November, drying rates will be negligible.

Estimating dry down rates can also be considered in terms of Growing Degree Days (GDDs). Generally, it takes 30 GDDs to lower grain moisture each point from 30% down to 25%. Drying from 25 to 20 percent requires about 45 GDDs per point of moisture. In September we average about 10 to 15 GDDs per day. In October (as things cool down) the rate drops to 5 to 10 GDDs per day. However, note that the above estimates are based on generalizations, and it is likely that some hybrids vary from this pattern of drydown.

Some of our past research evaluating corn drydown provides insight on effects of weather conditions on grain drying. During a warm, dry fall, grain moisture loss per day ranged from 0.76 to 0.92%. During a cool, wet fall, grain moisture loss per day ranged from 0.32 to 0.35%. Grain moisture losses based on GDDs ranged from 24 to 29 GDDs per percentage point of moisture (i.e., a loss of one percentage point of grain moisture per 24 to 29 GDD) under warm dry fall conditions, whereas under cool wet fall conditions, moisture loss ranged from 20 to 22 GDD per percentage point of moisture. The number of GDDs associated with grain moisture loss was lower under cool, wet conditions than under warm, dry conditions.

Harvest Aids for Corn and Soybeans

Authors: Mark Loux

Large weeds present at the time of crop harvest can slow the rate of crop maturation, slow the rate of harvest, and increase mechanical stress on equipment. There are only two ways to reduce the weed biomass in the field for easier harvest: 1) delay harvest until after a hard freeze (less than 25 degrees F for several hours); or 2) apply herbicides to control and dessicate the weeds. Waiting a week or so after the freeze or herbicide application will allow the weeds to dessicate and become more brittle.

Many glyphosate products can be used in a preharvest treatment in corn or soybeans – check labels for specific uses and rates. In corn, apply apply glyphosate at least 7 days before harvest when grain moisture is 35% or less. Corn should be physiologically mature (black layer formed) with maximum kernel fill complete. In soybeans, apply glyphosate after the pods have set and lost all green color, and at least 7 or 14 days before harvest, depending upon the glyphosate product. Most glyphosate product labels recommend avoiding preharvest application to corn or soybeans grown for seed, due to the potential for a reduction in seed germination or vigor.

Gramoxone can be applied as a preharvest treatment in field corn, seed corn, popcorn and soybeans. Apply when corn is mature, or after the black layer has formed at the base of the kernels, and at least 7 days before harvest. In soybeans, apply at least 15 days before harvest when at least 65% of the pods have reached a mature brown color or when seed moisture is 30% or less. Apply Gramoxone Max with crop oil concentrate (1.0 % v/v) or surfactant (0.25 % v/v). Use a spray volume of at least 20 gpa in ground applications.

Other Considerations:
1. The greener the weeds, the more effective the treatments (including a freeze) and greater likelihood of reducing weed seed viability.

2. The warmer the temperatures, the better and more rapid the kill.

3. The sunnier the weather, the better and more rapid the kill.

4. Glyphosate can control perennial weeds that are in the appropriate growth stage at the time of application.

5. Herbicide treatments and freezing weather will not necessarily force loss of fruit on black nightshade plants.

Time to Spray Warm-Season Perennials in Wheat Stubble

Mid-September is the time to spray wheat stubble fields to control warm-season perennials. Warm-season perennials include johnsongrass, wirestem muhly, common milkweed, hemp dogbane, bigroot morningglory (wild sweet potato), common pokeweed, perennial nightshades (horsenettle, clammy groundcherry, smooth groundcherry), Jerusalem artichoke, and a few others. These species are beginning to send photosynthate to various parts of the plant (rhizomes, stolons, tubers, roots, etc) in order to ensure their survival and expansion in the future. Systemic herbicides, especially glyphosate, applied at this time will move with the photosynthate to those plant parts, resulting in more effective control of the entire plant. Warm-season perennials should be treated with herbicide prior to the first frost, and prior to plant senescence. Now is not the ideal time to control cool-season perennials such as Canada thistle, dandelion, and quackgrass, which survive later into the fall.

If johnsongrass and wirestem muhly are the most important targets, apply glyphosate at a minimum rate of 1.1 pounds acid equivalent per acre (lbs ae/A). This rate corresponds to 33 ounces/A of Roundup WeatherMax, 36 ounces/A of Touchdown Total, and 48 ounces/A of most other 3.0 lbs ae/gallon glyphosate formulations. For the perennial broadleaf species mentioned above, the combination of glyphosate plus 2,4-D will generally be most effective. Use a glyphosate rate of at least 1.125 lbs ae/A and a 2,4-D rate of at least 1.0 pt/A, knowing more is better for certain species.

For the most effective long-term control of the warm-season perennials, plants should be at least 12 inches tall. For certain species such as johnsongrass, the minimum height should be 24 inches for maximum entire-plant control. For those perennials with an extensive creeping root or rhizome system, one application may not be enough to completely control all sections of those systems.

Archive Issue Contributors: 

State Specialists: Pat Lipps (Plant Pathology), Peter Thomison (Corn Production), Mark Loux (Weed Science), Jeff Stachler (Weed Science), Bruce Eisley (Entomology), and Ed Lentz (Agronomy). Extension Educators: Steve Foster (Darke), Todd Mangen (Mercer), Dusty Sonnenberg (Henry), Roger Bender (Shelby), Mark Koenig (Sandusky), and Harold Watters (Miami)

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.