CORN
Crop Observation and Recommendation Network

April 8-15, 2002
C.O.R.N. 2002-8

In This Issue:

A) Corn Profit Tips- Planting Decisions
B) Dealing With Dandelions
C) Warmer Weather And Alfalfa Weevil
D) Calculate And Calibrate Before Planting
E) Wheat In Ohio Is Ready To Grow

A) Corn Profit Tips-Planting Decisions - Peter Thomison and Ed Lentz CORN Questions

1. Complete Planting by May 10.
If soil conditions are dry, begin planting before the optimum date. (The recommended time for planting corn in northern Ohio is April 15 to May 10 and in southern Ohio, April 10 to May 10). Avoid early planting on poorly drained soils or those prone to ponding. Yield reductions resulting from "mudding the seed in" may be much greater than those resulting from a slight planting delay.

If growers have the equipment capability to plant more than half of their corn acres prior to the optimum planting date, then this should allow planting all the corn acres prior to the calendar date when corn yields begin to decline quickly. During the two to three weeks of optimal corn planting time, there is, on the average, about one out of three days when field work can occur. This narrow window of opportunity further emphasizes the need to begin planting as soon as field conditions will allow, even though the calendar date may be before the optimal date. As a guide, calendar date is more reliable than soil temperature for making the decision on when to begin to plant corn.
Other advantages of early planted corn are earlier maturity in the fall with more time for field drying and higher test weights. Early planting dates result in earlier plant emergence and faster canopy closure in the growing season. Faster canopy closure helps reduce early-season soil losses due to erosion. Early planted corn usually has better stalk quality and may reduce the exposure to various late insect and disease pest problems, such as European corn borer and gray leaf spot.

2. Plant Full-Season Hybrids First.
Once the full-season hybrids are planted, then alternately plant early-season and mid-season hybrids, to take full advantage of maturity ranges and to give the later-maturing hybrids the benefit of maximum heat-unit accumulation. Full-season hybrids generally show greater yield reduction when planting is delayed compared with short- to mid-season hybrids. In areas with longer growing seasons, consider planting some acreage to early hybrids to have new corn for the early market (which usually commands a premium price and thus partially offsets the income effect of the lower yield associated with early hybrids). Planting early hybrids first, followed by mid-season, and lastly the full-season hybrids spreads the pollination interval for all the corn acres over a longer time period and may be a good strategy for some drought-prone areas.

3. Adjust Seeding Depth According to Soil Conditions.
Plant between 1-1/2 to 2 inches deep to provide for frost protection and adequate root development. In April, when the soil is usually moist and evaporation rate is low, seed should be planted shallower no deeper than 1-1/2 inches. As the season progresses and evaporation rates increase, deeper planting may be advisable. When soils are warm and dry, corn may be seeded more deeply up to 2 inches on non-crusting soils. Consider seed-press wheels or seed firmers to ensure good seed-soil contact. One risk associated with shallower planting depths is the possibility of poor development of the permanent (or secondary) root system if the crown is at or near the soil surface, some of the permanent roots may not grow under hot, dry conditions (resulting in the "rootless" and "floppy" corn syndromes). Another potential risk from planting less than 1-1/2 inches is shoot uptake of soil-applied herbicides. Seeding depth should be monitored periodically during the planting operation and adjusted for varying soil conditions. Irregular planting depths contribute to uneven plant emergence, which can reduce yields.

4. Adjust Seeding Rates on a Field-by-Field Basis.
When seeding, adjust the seeding rates by using the yield potential of a site as a major criterion for determining the appropriate plant population. Higher seeding rates are recommended for sites with high-yield potential with high soil-fertility levels and water-holding capacity. On productive soils, with average yields of 160 bu/acre or more, final stands of 28,000 to 30,000 plants/acre or more may be required to maximize yields. High plant populations are also warranted when irrigation is used to maximize crop performance.

Lower seeding rates are preferable when droughty soils or late planting (after June 1) limit yield potential. On soils that average 120 bu/acre or less, final stands of 20,000 to 22,000 plants/acre may be adequate for optimal yields. Under drought stress conditions, high plant populations do not cause significant yield reduction.
Planting rate or population can be cut to lower seed costs but this approach typically costs more than it saves. Most research suggests that planting a hybrid at suboptimal seeding rates is usually more likely to cause yield loss than planting above recommended rates (unless lodging becomes more severe at higher population levels). When planting occurs in cold soils, usually very early planting dates, the seeding rate should be 15% higher than the desired harvest population. Follow seed company recommendations to adjust the population for specific hybrids.

B) Dealing With Dandelions - Mark Loux CORN Questions

Dandelion has been a persistent problem in no-till corn and soybean production for years, but seems to have become even peskier over the past several years. Dandelion is relatively easily controlled in the fall with 2,4-D, but can be difficult to control in the spring (especially when it reaches the "head of lettuce" size). When not adequately controlled or at least suppressed prior to planting, dandelion can interfere with crop establishment and growth. We speculate that the recent increase in dandelion populations may be blamed partly on the use of herbicide programs consisting solely of glyphosate or glyphosate/2,4-D burndown followed by postemergence herbicides. Dandelion emerges primarily in May, and the failure to use preplant herbicides with residual activity (Canopy XL, Sencor, Valor, etc) may result in increased populations of dandelion in late spring. We have observed an abundance of dandelion seedlings in some of our no-till soybean studies in May and June where residual herbicides were not applied. These seedlings are not completely controlled by many postemergence herbicides. After lurking under the crop canopy for most of the season, small dandelions take the opportunity to become better established in the fall after soybeans are harvested. Those plants that reach a size of more than 4 to 6 inches in diameter the following spring are especially difficult to control.

Some suggestions for managing dandelion this spring:

• Tillage can effectively control dandelions, but it must be aggressive enough to completely disrupt them.
  
  
• Use the highest rate of 2,4-D ester labeled for the time of application. Assuming that soils will dry enough to allow soybean planting within the next 30 days, the rate for most 2,4-D products is limited to 0.5 lbs/A (1 pint/A of 4 lb/gal product). As mentioned in a recent C.O.R.N. article, Weedone 650 (Nufarm) is labeled at a rate of 1 lb/A up to 15 days before planting, and 0.5 lb/A between 7 and 15 days before planting. The higher rate can provide more effective dandelion control where it can be legally used.
  
  
• A study by Purdue turf scientists showed that 2,4-D was more effective on dandelion after a certain number of heat units had accumulated in spring, so applications too early in spring may be less effective. However, we wonder if the larger size and/or more advanced growth stage of dandelion later in spring reduces control.
  
  
• The activity of glyphosate can vary with plant size and growth stage, and environmental conditions. Apply at least 26 oz/A of UltraMax or 32 oz/A of other glyphosate products, and include 2,4-D ester and ammonium sulfate (17 lbs/100 gallons). Multiple applications of glyphosate in Roundup Ready soybeans can eventually control most dandelions, even if the burndown fails to do so adequately.
  
  
• Several treatments utilizing herbicides other than glyphosate have provided rapid and effective control of dandelion. These include: Canopy XL plus Gramoxone Max plus 2,4-D; Canopy XL + Gramoxone Max; and Sencor plus 2,4-D plus Gramoxone Max. In a dandelion control study we conducted last spring, the mixture of Canopy XL, 2,4-D, and Gramoxone Max applied 30 days before soybean planting resulted in 98% control of dandelions by the time of soybean planting, versus not greater than 75% for most other treatments applied at that time. When applied 7 days before planting, a mixture of 2,4-D, Gramoxone Max, and Sencor or Canopy XL resulted in at least 85% control 14 days later. Even without the 2,4-D, a mixture of Canopy XL and Gramoxone Max controlled 89% of the dandelions. Ratings a month later showed Canopy XL to be more effective than Sencor in these mixtures. We had similar results in a study we conducted way back in the early 1990's with mixtures of Preview plus Gramoxone Max (I'm getting to be an old-timer here). While a mixture of Valor plus glyphosate was not especially effective in this study, we did not have Valor in combination with 2,4-D plus glyphosate or Gramoxone Max.
  
  
• Preplant application of herbicides with residual activity may reduce the population of new seedlings that emerges after planting. We suspect that most soil-applied broadleaf herbicides have at least some activity on newly emerging dandelion, but have little information to make specific recommendations.
  

C) Warmer Weather And Alfalfa Weevil - Bruce Eisley CORN Questions

The warmer temperatures this week means that we need to think about scouting alfalfa for alfalfa weevil (AW) in the near future. We have not had any reports of weevils or damage from weevil because of the colder temperatures this spring. We would suggest that scouting should begin when approximately 200 heat units at base 48 have accumulated. At this time heat unit accumulations are approximately 80 for southern Ohio, 70 for central Ohio and 40 for northern Ohio. Fields that have a south facing slope tend to warm up sooner and need to be checked for weevil earlier.

Alfalfa weevil scouting is accomplished by collecting a series of three
10-stem samples randomly selected from various locations in a field. Place the stem tip down in a bucket. After 10 stems have been collected, the stems should be vigorously shaken in the bucket and the number of larvae in the bucket counted. The shaking will dislodge the late 3rd and 4th instar larvae which cause most of the foliar injury. Close inspection of the stem tips may be needed to detect the early 1st and 2nd instar larvae. The height of the alfalfa should also be recorded at this time. Economic threshold is based on the number of larvae per stem, the size of the larvae and the height of the alfalfa. The detection of one or more large larvae per stem on alfalfa that is 12 inches or less in height indicates a need for rescue treatment. Where alfalfa is between 12 and 16 inches in height, the action threshold should be increased to 2 to 4 larvae per stem depending on the vigor of alfalfa growth. See the OSU Alfalfa Weevil FactSheet (http://ohioline.osu.edu/ent-fact/0032.html) for more on alfalfa weevil scouting and thresholds.

Chemicals currently labeled for use on alfalfa for alfalfa weevil include:

Ambush* @ 6.4 to 12.8 fl oz/A
Baythroid* 2 @ 1.6 to 2.8 fl oz/A
Furadan* 4F @ ½ to 1 pint/A
Guthion* Solupak 50WP @ ¾ to 1 lb/A
Imidan 70-W @ 1 to 1.33 lb/A
Lannate* LV @ 3 pint/A
Lannate* SP @ 1 lb/A
Lorsban* 4E @ 1 to 2 pint/A
Malathion @ (check label for rate)
Mustang* @ 2.4 to 4.3 fl oz/A
Pounce* 3.2EC @ 4 to 8 fl oz/A
Sevin 80S @ 1-7/8 lb/A
Warrior* 1CS @ 2.56 to 3.84 fl oz/A

* Use is restricted to certified applicators.

D) Calculate And Calibrate Before Planting - Jim Beuerlein CORN Questions

Reducing soybean seeding rate is a sure way to reduce costs and increase profit, but the calibration of drills and some planters is difficult because they do not singulate seed in the seed metering process. Therefore we must look at how many seeds are placed in each foot of row and then make adjustments to the seed meters. But how do we figure how many seeds should be placed in a foot of row in the first place?

Following is an easy way to calculate seed spacing for any row width and seeding rate:

Dividing the number of square inches per acre (6,272,640) by the seeding rate (seeds/acre) gives the number of square inches per seed.

Dividing that number by the row spacing in inches gives the spacing between seeds in the row.

Following are the calculations if you want to plant 175,000 seeds per acre in 7.5" rows:

6,272,640 square inches/acre (divided by) 175,000 seeds per acre
= 35.8 square inches

35.8 square inches per seed (divided by) 7.5 in row spacing
= 4.8 inch spacing between seeds

12 inches per foot of row (divided by) 4.8 inches between seed
=2.5 seeds per foot of row

This process works for any crop, seeding rate or row spacing.

E) Wheat In Ohio Is Ready To Grow - Pat Lipps and Dennis Mills CORN Questions

As of the first week of April, the condition of the wheat crop varies greatly across the state of Ohio from north to south. The wheat has shown some reasonable growth in the southern regions of the state, but in the north little if any regrowth has occurred up to now. The forecasted warmer weather for the next week or more will promote dramatic growth over this period as plants develop new roots and new leaves.

Wheat in southern Ohio is on schedule as compared to what we have seen over the past few years. Adequate moisture and temperatures should promote normal development of the crop in these regions. In the northern regions where spring green up has been hindered by available heat units, the wheat is a bit behind schedule. However, wheat can make up time quickly with sufficiently warm temperatures.

In Northwest Ohio that suffered stand losses from saturated soils last fall, the wheat crop is still quite variable from field to field. We visited some of the more severely damaged fields in Putnam Co. last week to see how the replanted wheat was growing in that area. We were impressed with the relatively good growth of the wheat that was replanted in early November. Most of the replanted fields had uniform stands of plants with from 2 to 4 tillers per plant. Some of the wheat replanted later in November had plants with only one tiller. The chances of these plants making more tillers this spring is becoming more risky as time passes. There is only about two more weeks of short day lengths that will allow for more tillering before day length and warm weather will initiate the stem elongation growth phase and tillering will stop. Those farmers that replanted fields using high seeding rates probably did the right thing since most have sufficient tiller numbers to make a wheat crop even without additional increase in tiller numbers. We consider this nothing short of a miracle since the odds are against having weather conditions favorable for wheat growth throughout November and December. Fields that were not replanted in this area are in poor shape and will likely be converted to a different crop later this spring.

Wet field conditions continue to hamper farmers from applying nitrogen to their wheat fields. Those fields that had a nitrogen application at planting are probably not yet at risk of this affecting yield. Additionally, the extended warm period last fall and the several warm periods over winter probably promoted release of nitrogen from soil organic matter. The fall applied nitrogen and that which is released in the soil should supply nearly all the required nitrogen for early growth and tiller development. Wheat does not begin to use larger amounts of nitrogen until it reaches the jointing or stem elongation growth stage (Feekes growth stage 6). Regardless, since we are now approaching mid April growers should apply the spring top dress to wheat as soon as field conditions permit.

What is the yield potential for this years wheat crop? Right now it is too early to tell. We look at a wheat crop as a series of management stages. At each stage, from planting through harvesting, management decisions need to be made depending on the condition of the wheat and what the weather will permit you to do. At this point all we can say is that most fields have sufficient tiller numbers to attain normal yields. These fields were planted on time and had good stands last fall. Other fields are more at risk. The weather conditions during April, May and June will dictate the actual yield potential of all fields.

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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.

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