May 1, 1998 Vol. 98.4
IN THIS ISSUE:
- Mark Your Calendar
- Weed Science Field Days - Landisville - July 16, 1998 and Rock Springs - July 17, 1998
- Penn State Agronomic Field Diagnostic Clinic - Rock Springs - July 22 & 23, 1998
- Penn State's Ag Progress Days - August 18, 19, 20, 1998
- Production
- Thoughts on Soybean Establishment
- Sulfur and Boron on Forage
- Pest Management
- Predicting Weed Emergence
- Corn Herbicide-Insecticide and Herbicide-Herbicide Restrictions
- Delayed Pre Herbicide Applications in Corn
- Herbicide Resistant Crops: Their Fit in the Northeast (Part III)
- Potato Leafhoppers, They Aren't Here Yet
- Precision Vision
- Calibrating Boom Sprayers
Production:
Thoughts on Soybean Establishment
Soybean planting will be in full force shortly. Establishing a vigorous uniform stand is key to profitable yields. The following are a few points to consider as we enter the planting season.
- Soybean seed are more sensitive to rough handling prior to and during the planting operation. Their chemical composition and thin seed coat make them more prone to damage then other grain seed. Therefore, do not drop bags of seed and be sure planters, particularly drills, are adjusted so the seed coat is not broken during the planting operation.
- Soybean seed require more water for germination then many other grain crops. This is the reason the old adage "if the soil is dry, don't try" is appropriate for soybean establishment. In addition to adequate soil moisture, there should be good seed to soil contact to assure adequate water movement into the seed.
- Soybeans can be established with any tillage-planting system. It is critical however, that enough tillage occur to provide a seedbed that is adequate for proper planter operation.
- Seed should be placed 1 to 1.5 inches deep. Planters should be adjusted so that the seed depth is as uniform as possible.
- The optimum planting date for soybean is the same as the optimum date for corn. It is normally suggested however, to plant corn first and then immediately start planting soybeans. This is because corn tends to be more responsive to early planting.
- The desired plant population for full season soybeans is 150,000 plants per acre. This population is suggested for all row spaces. Seeding rates required to obtain the desired population will need to be adjusted relative to soil and planter conditions. The following are guidelines for making adjustments in seeding rates.
Increase the seeding rate per acre by:
5% for each rotary hoeing
10% for rough seedbeds
10% for short season varieties
10% for cold soils
15% for no-till.
Decrease the seeding rate per acre by:
10% if lodging is a problem
10% if planting a lodging susceptible variety.
7. Most soybeans in Pennsylvania are planted in narrow row spaces, seven to fifteen inches. Research indicates that yield will be higher in narrow rows then wide rows, especially when planted after mid-may. We suggest planting 30 inch rows by May 10 in order to reduce the yield loss potential from wide rows.
Elwood Hatley, Agronomy, CCA
Sulfur and Boron on Forage
Following is a brief summary of the situation in regard to the boron and sulfur needs of forage crops.
Sulfur
Sulfur deficiency is not a common problem in Pennsylvania. Conditions where sulfur deficiency might occur include: low organic matter soils, coarse textured (i.e. sandy soils), areas of high rainfall, and fields that do not have a history of manure application. Also, acid rain is a major contributor of sulfur in Pennsylvania.
Current soil tests for sulfur are not very reliable. The best approach to diagnosing a sulfur problem is to use plant tissue analysis. It is critical when using plant analysis that the proper sample is taken at the appropriate stage of growth. For alfalfa, as an example, the top 1/3 of the plant should be sampled between bud and 1/10 bloom. If sulfur is sufficient, the sulfur analysis of this alfalfa sample should be between 0.25 and 0.50%. For cool season grasses the upper leaves should be sampled just prior to harvest stage. The sufficiency level for forage grasses is between 0.2 and 0.5 %. It has also been found that the ratio of nitrogen to sulfur in plant tissue is a good indicator of whether sulfur is adequate or deficient. For example, a nitrogen to sulfur ratio greater than 11 to 1 is an indication of sulfur deficiency in alfalfa. Note that sulfur is not run routinely by the Ag Analytical Services Lab at Penn State. They will run it if you indicate on the information sheet that you send with the sample that you want sulfur. There is an additional $6 fee to have sulfur run. Payment should be included with the sample.
If sulfur is found to be deficient, elemental sulfur, gypsum and sul-po-mag are common materials that can be used to correct the deficiency. Also, ammonium sulfate, which is 24% sulfur, can be used as the nitrogen source on grasses. Grass crops require around 8 to 12 lbs. of sulfur per acre and legume crops require 20 to 25 lbs. of sulfur per acre. These requirements can be used as guides for determining the rate of sulfur to apply if a sulfur deficiency is suspected.
Boron
Alfalfa has a high boron requirement, while the grasses have a low boron requirement. Other legumes are somewhere in between in their boron requirement. Alfalfa will remove about 0.05 lbs. of boron per ton of hay equivalent. A soil test level for boron greater than 1 ppm is considered adequate for alfalfa and greater than 0.5 is considered adequate for the other forage crops. The sufficiency level for plant analysis for boron in the top 1/3 of the alfalfa plant, sampled between bud and 1/10 bloom is 30 ppm. This can be compared to the sufficiency level for clover, which is 20 ppm boron in the tissue and the grasses, which require 5 to 10 ppm in the tissue. The common symptom of boron deficiency in alfalfa is "alfalfa yellows", stunted yellow alfalfa plants. This is usually associated with drought conditions. In Pennsylvania, it is routinely recommended that 2 lbs. of boron be applied when alfalfa is topdressed with fertilizer. If a serious boron deficiency is suspected based on soil tests or plant analysis the rate may be increased up to 4 lbs. of boron per acre. Because corn is somewhat sensitive to boron toxicity, do not apply excessive boron on fields that will be rotated to corn.
Douglas Beegle, Agronomy, Soils
Pest Management:
Predicting Weed Emergence
There is a fair amount of interest, particularly in the scientific community on trying to predict when certain weeds emerge. Like many organisms, weedy plants have an optimum temperature and moisture regime for growth and development including seed germination, vegetative growth, and reproduction. If we could predict when certain weed species emerge, we could:
- Optimize the time necessary for scouting
- Better match control strategies such as:
- Optimize time for tillage and crop planting to reduce weed density.
- Maximize effectiveness of mechanical controls (i.e. rotary hoeing and cultivation).
- Strategically time burndown and post herbicide applications.
Some recent research at Iowa State University as well as some work by USDA scientists in Minnesota has examined period of weed emergence. The Iowa study found that most weed species have one or more periods of high emergence and that although weeds don't emerge at the same time each year (due to varying climate), they do often emerge in the same sequence. The time of weed emergence may influence which weeds are most serious in a particular field. Table 1 groups weeds by their relative time of emergence compared to a spring seeded crop such as corn or soybean. This table was developed in part by a group of weed scientist from the North Central Region of the U.S. As an example, early planted corn could be plagued by lambsquarters, smartweed, and giant ragweed, while double-crop soybeans more frequently have fall panicum, jimsonweed, or annual morningglory problems if control measures are not implemented to manage for these weeds. These Iowa scientists are currently doing field experiments trying to increase our knowledge in this area.
| Before Crop | With Crop | After Crop | ||||
|---|---|---|---|---|---|---|
| Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6 | Group 7 |
| dandelion white cockle wild mustard |
giant ragweed quackgrass lambsquarters smartweed |
common ragweed velvetleaf wild buckwheat |
giant foxtail Canada thistle cocklebur pigweed sp. nutsedge |
green foxtail milkweed hemp dogbane yellow foxtail barnyard grass wirestem muhly |
ground cherry nightshade shattercane |
fall panicum witchgrass jimsonweed annual morningglory |
The USDA scientists in Minnesota took this process a step further and develop a computer model that relies on rainfall and growing degree days (GDD) to help predict weed emergence. The software was developed by Reese and Forcella to help predict :
- Weed emergence potential
- Weed emergence timing
- Weed seedling height
Although the software is still in the developmental stages, it could eventually be used to help time different weed management tactics. We are planning to test the software in some of our field research trials this summer. If anyone is interested in this software, it is a Windows or PC based application, is free, and is downloadable via a USDA web site: http://www.infolink.morris.mn.us/~lwink/products/weedcast.htm (3.6 meg). If you try it, let me know what you think.
Bill Curran
Corn Herbicide-Insecticide and Herbicide-Herbicide Restrictions
A number of restrictions exist with corn herbicide combinations. Here is a quick summary of what's on the labels. Products not included in the following table generally do not have specific restrictive statements concerning tank-mixing. For more detail, see the most recent label.
| Table 2. | |
|---|---|
| Herbicide | Precautions |
| Accent (post) |
|
| Basis (pre or post) |
|
| Basis Gold (post) |
|
| Beacon (post) |
|
| Broadstrike + Dual (pre) |
|
| Exceed (post) |
|
| Hornet (soil applied) |
|
| Hornet (post) |
|
| Liberty (post) |
|
| Lightning (e. post) |
|
| Permit (post) |
|
| Resource (post) |
|
| Scorpion III (post) |
|
Bill Curran and Dwight Lingenfelter, Agronomy
Delayed Pre Herbicide Applications in Corn
A number of residual herbicides can be applied after planting up until corn and weeds reach a certain size or growth stage. The greatest risk of failure comes with trying to control annual grasses such as foxtail and panicum after they emerge.
Several products are now available to control emerged grasses (Accent, Basis, Pursuit on IMI-corn Poast/Poast Plus for Poast Protected/SR corn, Liberty for glufosinate-resistant corn, and Roundup for Roundup-Ready corn.) Certain tank-mixes containing one of these grass herbicides will provide control of emerged grasses plus residual control. Because of their recent introduction, few residual herbicides are labeled with some of these grass herbicides in tank-mixture. However, Frontier and Prowl are labeled with Accent and a number of residual products are labeled with Pursuit. Also, several products can be tank-mixed with Poast or Poast Plus, Liberty, and Roundup. For most products, do not apply in liquid fertilizer if corn has emerged. Some early-postemergence considerations are listed in the following table.
| Table 3. Maximum corn and weed size for delayed preemergence herbicide applications. | ||
|---|---|---|
| Herbicides | Maximum corn size | Maximum weed size |
| Atrazine | 12 inches | 1.5 inches |
| Atrazine + Bladex 90 DF or Extrazine II 90 DF | 4-leaf | 1.5 inches |
| Banvel or Marksman + Bladex 80W or 90DF | 4-leaf | 1.5 inch grass |
| Banvel or Marksman + Dual or Lasso EC | 3 inches | 2-leaf grass |
| Banvel or Marksman + Frontier | 8 inches | 1 inch grass |
| Marksman + Prowl | 2-leaf | 1 inch grass |
| Basisa | 4-leaf, 2 collars, or 6 inches | 2 inches (see label for weed species) |
| Basis Goldb | 12inches or 6 collars | depends on weed (see label) |
| Bicep II + Prowl | 4-leaf or 2 collars | 1 to 2-leaf |
| Bladex 80W or 90DF | 4-leaf | 1.5 inches |
| Bullet or Micro-Tech + atrazine | 5 inches | 2-leaf |
| Dual or Micro-Tech + atrazine, Bullet | 5 inches | 2-leaf |
| Dual II, (Dual II + atrazine), Bicep II, Bicep II Magnum, Bicep Lite II, Bicep Lite II Magnum | 5 inches | 2-leaf |
| Dual II or Dual II Magnum + Banvel | 5 inches | 3 inch pigweed |
| Dual II + Marksman | 3 inches | 2-leaf |
| Frontier | 8 inches | before emergence or by tank-mix partner |
| Frontier + Accentc | 8 inches | 3 inch |
| Frontier + Beacon | 8 inches | depends on weed (see Beacon label) |
| Guardsman | 8 inches | 1.5 inches |
| Harness or Harness Xtrae | 11 inches or by tank-mix partner | before emergence or by tank-mix partner |
| Hornet | 24 inches | < 8 inches |
| Princep | before emergence | before emergence |
| Prowl + Accentd or Prowl + Accent + Beacond | 6-leaf | see herbicide labels |
| Prowl + Atrazine, Prowl + Bladex 90DF, or Prowl + Banvel | 4-leaf | 1 inch |
| Prowl + Beacond | 6-leaf | depends on weed (see Beacon label) |
| Prowl + Poast Plusf | 6-leaf | depends on grass (see Poast Plus label) |
| Python WDG | 2 inches | before weed emergence |
| Surpass, Surpass 100, FulTime, or TopNotchg | 11 inches or by tank-mix partner | before emergence or by tank-mix partner |
| a May be tank-mixed with Clarity/Banvel, Atrazine
90DF, and Marksman. b May be tank-mixed with Clarity/Banvel, Hornet, or Tough. c May use a reduced rate of Frontier and Accent under certain conditions. d Accent rate of 1/3 to 2/3 oz/acre and Beacon rate of 3/8 to 3/4 oz/acre; when tank-mixing all three herbicides-Accent rate is 0.33 oz/acre and Beacon is 0.38 oz/acre. e May be tank-mixed with Accent, Atrazine (Harness), Banvel or Clarity, Marksman, Permit, or Pursuit (IMI-corn). f Poast Plus rate of 12 to 24 oz/acre. (For use on Poast Protected corn only) g May be tank-mixed with a number of different products including Accent, Banvel or Clarity, Prowl, Pursuit (IMI-corn), etc. See a herbicide label for specific information. |
||
Bill Curran and Dwight Lingenfelter, Agronomy
Herbicide Resistant Crops: Their Fit in the Northeast (Part III)
The following is the last of a three part series on herbicide resistant crops. This article discusses some economic principles of herbicide resistant crops (HRC) in the Northeast. For previous discussions about herbicide resistant crops refer to the March 20 (Vol. 98:2) and April 17 (Vol. 98:3) issues of Field Crop News.
Economics of HRCs
The following tables provide a way to compare standard herbicide programs to programs that include a HRC. These tables should only be used as a rough comparison between the two systems. The values contained in these tables do NOT account for special marketing and rebate programs which are being offered by some companies. Carefully consider all agronomic and economic aspects of these programs before purchasing.
Evaluating the economics of herbicide resistant
crops
Step 1: Figure the cost of your current herbicide
program
In order to have a valid comparison, you need to include all
the costs associated with your current herbicide program. This would include
not only the cost of the herbicides, but also the cost of application,
surfactants, crop oil concentrate, and any other spray additives. It is
especially important to factor in the number of applications currently
required, because additional trips across the field are costly. The cost of
spray additives is often minor, but should be included because often times the
new product formulations used on herbicide resistant crops (e.g., Roundup
Ultra) already have such costs included in their price.
Step 2: Figure the cost of the herbicide resistant
crop program
The use of a herbicide resistant crop could be used by
producers for different production goals. One situation might allow producers
to reduce herbicide rates for standard preemergence programs and "clean-up"
problem weeds postemergence. A second situation may be a standard program which
allows for a postemergence application of Roundup Ultra, Liberty, Poast (corn),
or Synchrony STS (soybeans), if needed. A third situation may be the use of a
simplified herbicide program which only includes Roundup Ultra or Liberty. It
is important to account for the herbicide rate and number of applications
required, because more than one application may be necessary to get desired
levels of weed control. The higher seed cost for HRCs should also be added to
the cost of spray materials and application cost because this additional cost
relates to a change in the weed management program.
The data in Table 4 can be used to estimate the relative cost differences between various herbicide programs for corn and soybeans. These numbers are estimates only; you should use your own costs if possible. Compare the cost of your current herbicide program to the cost of using an HRC program (including the difference in seed cost). If the cost of the HRC program is less expensive and at least as effective as what you are currently using, then you need to look at how changes in yield potential may erase this cost savings.
Step 3: How much can my yield change and still
leave me with the same profit?
One of the concerns with the use of
herbicide resistant crops is the possibility of yield lag. The promise of HRCs
is the ability to get better weed control, perhaps at lower cost. However,
these advantages can be quickly erased even for very modest yield declines.
Once you have figured the change in cost associated with the switch to
herbicide resistant crops, then you can estimate the yield change which would
leave you with the same profitability as before. The yield change depends on
the herbicide and seed cost differential and expected crop price. For a given
herbicide and seed cost differential, the yield change which will result in the
same profit will decrease as commodity prices increase. For example in Table 5,
if the new herbicide and seed cost is $10 cheaper (-10) than the standard
program for corn, then we could lose up to 4 bushels of corn at $2.50, but lose
only 3 bushels at $3.30 and stay at the same profit level as before.
In some cases, the increase in weed control due to the use of HRCs may lead to a yield increase. If the cost of herbicides is lower and yields are higher than it is obvious that such a change makes economic sense. However, if both the yield and herbicide and seed differential is higher than before, then Table 5 can be used to determine the yield increase needed to justify the additional cost. For example, if the herbicide and seed differential is $20 more expensive (+20) than the present conventional program, then a yield increase of 8 bushels would be needed at a corn price of $2.50/bu. If corn price was $3.30, however, only 6.1 bushels would be needed to overcome the cost difference.
How much yield change can you expect?--In the case of HRCs, two things are affecting yield potential; the HRC used and the change in herbicide program efficacy. Yield potential will vary from field depending on weed pressure and HRC suitability. The yield change numbers in Table 5 will give you an idea of the magnitude of changes which affect the profitability of using HRCs. As more HRC varieties and hybrids enter the market, better yield performance data will become available. Be cautious of "coffee-shop talk" or certain marketing ploys and try to rely on replicated research trials and results from your own experience.
| CORN | Compared to | SOYBEANS | Compared to | ||
|---|---|---|---|---|---|
| CORN HERBICIDE PROGRAM | standard pre only | standard pre+post program | SOYBEAN HERBICIDE PROGRAM | standard pre only | standard pre+post program |
| Standard pre grass & broadleaf program pre only (e.g., Bicep II + Prowl) | 0 | -13 | Standard pre grass & broadleaf program pre only (e.g., Broadstrike+Dual) | 0 | -22 |
| Standard grass & broadleaf program pre+post (e.g., Bicep II fb Exceed+Banvel) | +13 | 0 | Standard grass & broadleaf program pre+post (e.g., Broadstrike+Dual fb Storm) | +22 | 0 |
| Roundup Ready program half rate standard pre fb* Roundup post | +3 | -10 | Roundup Ready program Roundup post only |
-12 | -34 |
| Roundup Ready program full rate standard pre fb Roundup post | +11 | -2 | Roundup Ready program split, Roundup fb Roundup | +7 | -15 |
| Roundup Ready program Roundup post only |
-12 | -25 | Roundup Ready program half rate standard pre fb Roundup post | +7 | -15 |
| Roundup Ready program split, Roundup fb Roundup | +7 | -6 | Roundup Ready program full rate standard pre fb Roundup post | +19 | -3 |
| Roundup Ready program epost only (e.g., Harness Xtra fb Roundup) | +4 | -9 | Liberty Link program Liberty post only |
-6 | -28 |
| Liberty Link program half rate standard pre fb Liberty post | +9 | -4 | Liberty Link program split, Liberty fb Liberty | +19 | -3 |
| Liberty Link program full rate standard pre fb Liberty post | +17 | +4 | Liberty Link program half rate standard pre fb Liberty post | +13 | -9 |
| Liberty Link program Liberty post only |
-6 | -19 | Liberty Link program full rate standard pre fb Liberty post | +25 | +3 |
| Liberty Link program split, Liberty fb Liberty | +19 | +6 | STS program post only (e.g., Synchrony STS+Assure II) | -12 | -34 |
| Standard post grass & broadleaf program post only (e.g., Accent + Banvel) | +5 | -8 | |||
| Poast Protected program post only (e.g., Poast + Marksman) | -1 | -14 | |||
| *fb = followed by. | |||||
| Table 5. Yield change needed to compensate for difference in herbicide AND seed cost. | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CORN | |||||||||||||||
| Corn market price |
less expensive | same cost |
more expensive | ||||||||||||
| --------------------------------- | $$$ | --------------------------------- | |||||||||||||
| -35 | -30 | -25 | -20 | -15 | -10 | -5 | 0 | +5 | +10 | +15 | +20 | +25 | +30 | +35 | |
| -----bushels/acre----- | |||||||||||||||
| 2.00 | -17.5 | -15.0 | -12.5 | -10.0 | -7.5 | -5.0 | -2.5 | 0.0 | 2.5 | 5.0 | 7.5 | 10.0 | 12.5 | 15.0 | 17.5 |
| 2.10 | -16.7 | -14.3 | -11.9 | -9.5 | -7.1 | -4.8 | -2.4 | 0.0 | 2.4 | 4.8 | 7.1 | 9.5 | 11.9 | 14.3 | 16.7 |
| 2.20 | -15.9 | -13.6 | -11.4 | -9.1 | -6.8 | -4.5 | -2.3 | 0.0 | 2.3 | 4.5 | 6.8 | 9.1 | 11.4 | 13.6 | 15.9 |
| 2.30 | -15.2 | -13.0 | -10.9 | -8.7 | -6.5 | -4.3 | -2.2 | 0.0 | 2.2 | 4.3 | 6.5 | 8.7 | 10.9 | 13.0 | 15.2 |
| 2.40 | -14.6 | -12.5 | -10.4 | -8.3 | -6.3 | -4.2 | -2.1 | 0.0 | 2.1 | 4.2 | 6.3 | 8.3 | 10.4 | 12.5 | 14.6 |
| 2.50 | -14.0 | -12.0 | -10.0 | -8.0 | -6.0 | -4.0 | -2.0 | 0.0 | 2.0 | 4.0 | 6.0 | 8.0 | 10.0 | 12.0 | 14.0 |
| 2.60 | -13.5 | -11.5 | -9.6 | -7.7 | -5.8 | -3.8 | -1.9 | 0.0 | 1.9 | 3.8 | 5.8 | 7.7 | 9.6 | 11.5 | 13.5 |
| 2.70 | -13.0 | -11.1 | -9.3 | -7.4 | -5.6 | -3.7 | -1.9 | 0.0 | 1.9 | 3.7 | 5.6 | 7.4 | 9.3 | 11.1 | 13.0 |
| 2.80 | -12.5 | -10.7 | -8.9 | -7.1 | -5.4 | -3.6 | -1.8 | 0.0 | 1.8 | 3.6 | 5.4 | 7.1 | 8.9 | 10.7 | 12.5 |
| 2.90 | -12.1 | -10.3 | -8.6 | -6.9 | -5.2 | -3.4 | -1.7 | 0.0 | 1.7 | 3.4 | 5.2 | 6.9 | 8.6 | 10.3 | 12.1 |
| 3.00 | -11.7 | -10.0 | -8.3 | -6.7 | -5.0 | -3.3 | -1.7 | 0.0 | 1.7 | 3.3 | 5.0 | 6.7 | 8.3 | 10.0 | 11.7 |
| 3.10 | -11.3 | -9.7 | -8.1 | -6.5 | -4.8 | -3.2 | -1.6 | 0.0 | 1.6 | 3.2 | 4.8 | 6.5 | 8.1 | 9.7 | 11.3 |
| 3.20 | -10.9 | -9.4 | -7.8 | -6.3 | -4.7 | -3.1 | -1.6 | 0.0 | 1.6 | 3.1 | 4.7 | 6.3 | 7.8 | 9.4 | 10.9 |
| 3.30 | -10.6 | -9.1 | -7.6 | -6.1 | -4.5 | -3.0 | -1.5 | 0.0 | 1.5 | 3.0 | 4.5 | 6.1 | 7.6 | 9.1 | 10.6 |
| 3.40 | -10.3 | -8.8 | -7.4 | -5.9 | -4.4 | -2.9 | -1.5 | 0.0 | 1.5 | 2.9 | 4.4 | 5.9 | 7.4 | 8.8 | 10.3 |
| 3.50 | -10.0 | -8.6 | -7.1 | -5.7 | -4.3 | -2.9 | -1.4 | 0.0 | 1.4 | 2.9 | 4.3 | 5.7 | 7.1 | 8.6 | 10.0 |
| 3.60 | -9.7 | -8.3 | -6.9 | -5.6 | -4.2 | -2.8 | -1.4 | 0.0 | 1.4 | 2.8 | 4.2 | 5.6 | 6.9 | 8.3 | 9.7 |
| 3.70 | -9.5 | -8.1 | -6.8 | -5.4 | -4.1 | -2.7 | -1.4 | 0.0 | 1.4 | 2.7 | 4.1 | 5.4 | 6.8 | 8.1 | 9.5 |
| 3.80 | -9.2 | -7.9 | -6.6 | -5.3 | -3.9 | -2.6 | -1.3 | 0.0 | 1.3 | 2.6 | 3.9 | 5.3 | 6.6 | 7.9 | 9.2 |
| 3.90 | -9.0 | -7.7 | -6.4 | -5.1 | -3.8 | -2.6 | -1.3 | 0.0 | 1.3 | 2.6 | 3.8 | 5.1 | 6.4 | 7.7 | 9.0 |
| 4.00 | -8.8 | -7.5 | -6.3 | -5.0 | -3.8 | -2.5 | -1.3 | 0.0 | 1.3 | 2.5 | 3.8 | 5.0 | 6.3 | 7.5 | 8.8 |
| SOYBEANS | |||||||||||||||
| Soybean market price |
less expensive | same cost |
more expensive | ||||||||||||
| --------------------------------- | $$$ | --------------------------------- | |||||||||||||
| -35 | -30 | -25 | -20 | -15 | -10 | -5 | 0 | +5 | +10 | +15 | +20 | +25 | +30 | +35 | |
| -----bushels/acre----- | |||||||||||||||
| 5.00 | -7.0 | -6.0 | -5.0 | -4.0 | -3.0 | -2.0 | -1.0 | 0.0 | 1.0 | 2.0 | 3.0 | 4.0 | 5.0 | 6.0 | 7.0 |
| 5.10 | -6.9 | -5.9 | -4.9 | -3.9 | -2.9 | -2.0 | -1.0 | 0.0 | 1.0 | 2.0 | 2.9 | 3.9 | 4.9 | 5.9 | 6.9 |
| 5.20 | -6.7 | -5.8 | -4.8 | -3.8 | -2.9 | -1.9 | -1.0 | 0.0 | 1.0 | 1.9 | 2.9 | 3.8 | 4.8 | 5.8 | 6.7 |
| 5.30 | -6.6 | -5.7 | -4.7 | -3.8 | -2.8 | -1.9 | -0.9 | 0.0 | 0.9 | 1.9 | 2.8 | 3.8 | 4.7 | 5.7 | 6.6 |
| 5.40 | -6.5 | -5.6 | -4.6 | -3.7 | -2.8 | -1.9 | -0.9 | 0.0 | 0.9 | 1.9 | 2.8 | 3.7 | 4.6 | 5.6 | 6.5 |
| 5.50 | -6.4 | -5.5 | -4.5 | -3.6 | -2.7 | -1.8 | -0.9 | 0.0 | 0.9 | 1.8 | 2.7 | 3.6 | 4.5 | 5.5 | 6.4 |
| 5.60 | -6.3 | -5.4 | -4.5 | -3.6 | -2.7 | -1.8 | -0.9 | 0.0 | 0.9 | 1.8 | 2.7 | 3.6 | 4.5 | 5.4 | 6.3 |
| 5.70 | -6.1 | -5.3 | -4.4 | -3.5 | -2.6 | -1.8 | -0.9 | 0.0 | 0.9 | 1.8 | 2.6 | 3.5 | 4.4 | 5.3 | 6.1 |
| 5.80 | -6.0 | -5.2 | -4.3 | -3.4 | -2.6 | -1.7 | -0.9 | 0.0 | 0.8 | 1.7 | 2.6 | 3.4 | 4.3 | 5.2 | 6.0 |
| 5.90 | -5.9 | -5.1 | -4.2 | -3.4 | -2.5 | -1.7 | -0.8 | 0.0 | 0.8 | 1.7 | 2.5 | 3.4 | 4.2 | 5.1 | 5.9 |
| 6.00 | -5.8 | -5.0 | -4.2 | -3.3 | -2.5 | -1.7 | -0.8 | 0.0 | 0.8 | 1.7 | 2.5 | 3.3 | 4.2 | 5.0 | 5.8 |
| 6.10 | -5.7 | -4.9 | -4.1 | -3.3 | -2.5 | -1.6 | -0.8 | 0.0 | 0.8 | 1.6 | 2.5 | 3.3 | 4.1 | 4.9 | 5.7 |
| 6.20 | -5.6 | -4.8 | -4.0 | -3.2 | -2.4 | -1.6 | -0.8 | 0.0 | 0.8 | 1.6 | 2.4 | 3.2 | 4.0 | 4.8 | 5.6 |
| 6.30 | -5.6 | -4.8 | -4.0 | -3.2 | -2.4 | -1.6 | -0.8 | 0.0 | 0.8 | 1.6 | 2.4 | 3.2 | 4.0 | 4.8 | 5.6 |
| 6.40 | -5.5 | -4.7 | -3.9 | -3.1 | -2.3 | -1.6 | -0.8 | 0.0 | 0.8 | 1.6 | 2.3 | 3.1 | 3.9 | 4.7 | 5.5 |
| 6.50 | -5.4 | -4.6 | -3.8 | -3.1 | -2.3 | -1.5 | -0.8 | 0.0 | 0.8 | 1.5 | 2.3 | 3.1 | 3.8 | 4.6 | 5.4 |
| 6.60 | -5.3 | -4.5 | -3.8 | -3.0 | -2.3 | -1.5 | -0.8 | 0.0 | 0.8 | 1.5 | 2.3 | 3.0 | 3.8 | 4.5 | 5.3 |
| 6.70 | -5.2 | -4.5 | -3.7 | -3.0 | -2.2 | -1.5 | -0.7 | 0.0 | 0.7 | 1.5 | 2.2 | 3.0 | 3.7 | 4.5 | 5.2 |
| 6.80 | -5.1 | -4.4 | -3.7 | -2.9 | -2.2 | -1.5 | -0.7 | 0.0 | 0.7 | 1.5 | 2.2 | 2.9 | 3.7 | 4.4 | 5.1 |
| 6.90 | -5.1 | -4.3 | -3.6 | -2.9 | -2.2 | -1.4 | -0.7 | 0.0 | 0.7 | 1.4 | 2.2 | 2.9 | 3.6 | 4.3 | 5.1 |
| 7.00 | -5.0 | -4.3 | -3.6 | -2.9 | -2.1 | -1.4 | -0.7 | 0.0 | 0.7 | 1.4 | 2.1 | 2.9 | 3.6 | 4.3 | 5.0 |
Jayson Harper, Ag Economics, William Curran, and Dwight Lingenfelter, Agronomy
Potato Leafhoppers, They Aren't Here Yet
Several people in Southeastern Pennsylvania have reported alfalfa with symptoms very similar to potato leafhopper feeding and insects which looked a lot like potato leafhoppers. However, after sweeping the suspect fields for leafhopper and examining the alfalfa plants, Dennis Calvin determined that they WERE NOT potato leafhopper but a relative that doesn't cause much damage to alfalfa. Now the real question which remains unanswered is "What caused the symptoms on the alfalfa if it wasn't potato leafhopper?"
Marvin Hall
Precision Vision:
Calibrating Boom Sprayers
The dogwoods are in full bloom here in central Pennsylvania. I was talking with a colleague last week as we were visiting a farm in the eastern part of the state, and he mentioned that the dogwoods make good indicators for scheduling corn planting. Perhaps we should have dogwood observers as well as weather observers who compute growing degree days. Think about it: perhaps a new tool for the farmers "the Dogwood Index"!
There are lots of sprayer manufacturers and a couple of spraytip and spray accessory manufacturers. TeeJet nozzles (Spraying Systems, Co.), Delavan, and CP Products offer nozzles and accessories. Many of the spray rigs in Pennsylvania seem to be fitted with either TeeJet or Delavan. The point here is that regardless of the manufacturer, if the nozzles are worn and the sprayer pressure is not properly adjusted, the right amount of chemical or nutrient is not going to get applied to the right spot and either damage will occur or the farmer will spend more money than is necessary.
Sprayer Calibration (1) readies your sprayer for operation and (2) diagnoses tip wear. This will give you optimum performance of your spray tips.
Equipment Needed for the Calibration Procedure:
- Calibration Container
- Calculator
- Cleaning Brush
- One new spray tip matched to the nozzles on your sprayer
- Stopwatch or wristwatch with second hand
- Nozzle Catalog or pressure/gpm rating sheet for your spray nozzles
STEP NO. 1 - Check Your Tractor/Sprayer Speed!
Knowing your real sprayer speed is an essential part of accurate spraying. Speedometer readings and some electronic measurement devices can be inaccurate because of wheel slippage. Check the time required to move over a 100 or 200 foot strip on your field. Fence posts can serve as permanent markers. The starting post should be far enough away to permit your tractor/sprayer to reach desired spraying speed. Hold that speed as you travel between the "start" and "end" markers. Most accurate measurement will be obtained with the spray tank half full. Use the following formula to determine your sprayer speed in miles per hour. When the correct throttle and gear setting are identified to get the DESIRED SPRAYING SPEED, mark your tachometer or speedometer to help you control and maintain this vital part of accurate chemical application.
Speed in mph = [Distance (ft) x 60 ] / [Time (seconds) x 88]
STEP NO. 2 - Determining the Spraying Control Inputs
Before spraying, record the following:
1. Nozzle type on your sprayer (i.e. TeeJet 8004 Flat)
Note: Make sure all nozzles are identical
2. Recommended application
volume from manufacturers label (i.e. 20 GPA)
3. Measured sprayer
speed from Step 1 (i.e. 6.5 mph)
4. Nozzle spacing on your sprayer in
inches (W for formula below) (i.e. 20 inches)
STEP NO. 3 - Calculating Required Nozzle Output
Determine GPM nozzle output from formula.
Formula: GPM = [GPA x mph x W] / [5940]
Example: GPM per nozzle = (20 x 6.5 x 20 ) divided by 5940 = 0.438 GPM This is the recommended GPM to deliver the amount of chemical at your measured sprayer speed.
STEP NO. 4 - Setting the Correct Pressure
a. Turn on your sprayer and check for leaks or
blockage.
b. Inspect and clean, if necessary, all tips and strainers
with cleaning brush. An old toothbrush works fine.
c. Replace one tip
and strainer with an identical new tip and strainer on sprayer boom.
d. Check appropriate tip selection table and determine the pressure required to
deliver the nozzle output calculated from the formula in Step 3 for your new
tip. Since all the tabulations are based on spraying water, conversion factors
must be used when spraying solutions which are heavier or lighter than water.
(see the note at the end of this procedure about conversion
factors).
Example: (Using above inputs) Refer to your TeeJet table for 8004 flat spray tip. The table shows that this nozzle should deliver 0.42 GPM at 45 psi and 0.49 GPM at 60 psi.
e. Turn on your sprayer and adjust pressure. Collect and measure the volume of the spray from the NEW tip for one minute in the collection jar. Fine tune the pressure regulator until you collect .438 GPM. If the pressure required is too high for your pump, go to the next size larger nozzle tip.
For example, switch to a TeeJet 8005 which would deliver 0.43 GPM at 30 psi. This lower pressure also cuts down on the droplet size and decreases spray drift. That is a topic for another time. You could also slow down the sprayer travel speed and get less nozzle GPM required for the manufacturer's application rate per acre.
You have now adjusted your sprayer to the proper pressure. It will properly deliver the application rate specified by the chemical manufacturer...at your measured sprayer speed.
STEP NO. 5 - Checking Your System for Worn Spray Tips
Now, check the flow rate of each tip. If the flow rate of any tip is 10 percent greater or less than that of the newly installed spray tip, recheck the output of that tip. If only one tip is faulty, replace with new tip and strainer and your system is ready for spraying. However, if a second tip is defective, replace all tips on the entire boom. Then check the flow rate of all new tips. This may sound unrealistic, but two worn tips on a boom are ample indication of tip wear problems. Replacing only a couple of worn tips invites potentially serious application problems. This is also a good time to reconsider purchasing some of the new low drift/low wear/low pressure nozzles on the market. They have been proven to save money on chemicals and spray drift damage. This is critical if you are using some of the new Roundup Ready crops.
Banding and Directed Applications:
The only difference between the above procedure and calibrating for banding or directed applications is the input value used for "W" in the formula in Step No. 3.
For single nozzle banding or boomless applications...W = Sprayed band width or swath width (in inches).
For multiple nozzle directed applications...
W = Row spacing (in inches) divided by the number of nozzles per row.
This sprayer calibration procedure is taken from the TeeJet Catalog 45A, and used with permission.
If you are spraying solutions other than water, the specific gravity of the new solution (or the pounds per gallon of the solution makes a difference on the required GPM per nozzle. Contact your extension agent or request our sprayer fact sheet for an example of how to use different weights per gallon of solution to calibrate your nozzle tips. This calibration procedure given above is used for solutions that are close to the weight of water at 8.34 lbs/gallon. If you are using 28% nitrogen which weighs 10.65 lbs/gallon, the conversion factor is 1.13. So you multiply the manufacturer's recommended gallons per acre of nitrogen solution by the conversion factor to get the equivalent gallons per acre of water. This is then used to calibrate your sprayer when using water as the calibrating solution.
That's all for this column. Call me or your extension agent if you need help with your sprayer calibration.
David Wagner, Ag Engineering, Precision Ag
| William S. Curran |
| Associate Professor Weed Science |
| email: wsc2@psu.edu |
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Website Address: http://fcn.agronomy.psu.edu/