April 20, 2006
In this issue
§ Sandhill crane repellent (Avitec) approved for the 2006 field season
§ Soybean seed applied inoculation
§ Mark your calendars: MSU Weed Tour and Crop Diagnostic Day dates
§ The clock is ticking for postemergence weed control strategies in sugar beets
§ Recommendations for successful establishment of Roundup Ready alfalfa
§ Effectiveness of burndown herbicides for winter annual and perennial weed control in corn and soybeans
§ Weed management in wheat
§ Benefits of using soil-applied residual herbicides in soybeans
§ Section 18 for Folicur
§ Nitrogen fertilizer management strategies
§ Planting strategies for Bt rootworm corn refuge areas
§ Considerations for planting soybeans early
§ Regional reports
§ Weather news
The EPA has approved a Section 18 application for Avitec,
a non-lethal crane repellent, on corn in
Avitec contains 9,10 anthraquinone, a reduced risk, natural bird repellent produced by plants. Anthraquinone is already used in several products as a goose repellent for parks, golf courses, schools, lawns etc. For agricultural use, the product Avitec will be available as both a powder and a liquid, so producers will be able to apply it as a planter box treatment or have seed treated by a commercial applicator. Avitec is not a restricted use pesticide.
Cranes pluck corn seed and seedlings out of the ground early in the season. Because sandhill cranes are a threatened species, Avitec seed treatment provides a way to repel the birds without harming them. Cranes detect the Avitec, and thus avoid feeding on the corn seed. However, cranes may still be present in a treated field eating other seeds or insects. Note that the Section 18 is to reduce crane damage in newly planted corn seed. It is not for use against any other bird species at this time.
Arkion Life Sciences LLC - producer of Avitec
International Crane Foundation - supported the Section 18
Baraboo, WI 1-608-356-9462
Michigan Department of Agriculture – has Section 18 labels on the web
http://www.michigan.gov/mda/0,1607,7-125-1569_16988_35290-127656--,00.html
Nitrogen fixation is a result of the symbiotic relationship
of Rhizobia bacteria and soybean plants. These bacteria fix atmospheric N2
into the NH4 form, which is useful to the plant. In return, the
plant provides the bacteria with carbon photosynthesis products (dicarboxylic
acids), which the bacteria use as food. Establishing rhizobia or inoculation in
a field that has never grown soybean is needed to ensure nitrogen fixation.
Elmore (1996) suggests when and how soybeans should be inoculated and provides
recommendations on inoculate type to use. Soybeans grown on soils without a
rhizobia population will use available soil nitrogen, and if soil nitrogen
levels are low because of soil type, soil erosion, etc., the symptoms of
nitrogen deficiency may occur. Field
studies in
In addition to the recommended short time period between
seed applied inoculant application and planting, there are other potential challenges
associated with proper soybean seed inoculation. Care should be taken in
applying inoculant to fungicide or insecticide treated seed. Fungicide and
insecticide labeling should be checked to ensure that the particular pesticide
product is compatible with Rhizobium inoculant. Potter (2004) conducted a field
trial to examine the effects of inoculating soybean seed with rhizobium, seed
applied insecticides and fungicides, and combining bacterial inoculant,
insecticidal and fungicidal products in southwest
Further, differences in root disease, soybean height,
nodulation or yield were not observed among treatments. A three year
Finally, Rhizobia do not function below pH 5.0 and molybdenum, which is important for Rhizobia nodule formulation, can be deficiencient at pH levels below 6.0. Liming of low pH soils is the best solution for these challenges.
1) Inoculates should be stored in a cool place and not exposed to the sun prior to use. Refer to product labels for specific handling recommendations.
2) The safest approach is to buy fresh inoculate each year.
3) Seed should be planted within four hours of inoculation. New products are being developed with a longer preplant application interval but data on the performance of these products is somewhat limited.
4) When applying a fungicide or using fungicide-treated seed, be sure the fungicide has dried before applying inoculate to the seed. Inoculate should not be mixed with fungicides and applied together. Refer to product labels for specific handling recommendations
5) When loading a drill or planter using an auger, inoculation materials (liquid or dry) should be added to the seed as it enters the auger for thorough application.
6) When loading a drill or planter from bags, fill the seed box to a depth of three inches and scatter the appropriate amount of inoculate over the seed and mix it in thoroughly. Continue to add seed in six-inch deep layers, treating each until the seed box is filled.
7) With some dry materials it may be desirable to slightly moisten seed to increase the adherence of inoculate. Individual seeds need no more than a 3 to 5 percent coating of dry material. Liquid materials will usually cover most of the seed.
8) Seeding equipment should be calibrated using treated seed.
9) Lime soils used for soybean production according to soil test recommendations.
Beuerline, J. (2004) Soybean inoculation; its science, use, and performance. http://agcrops.osu.edu/soybean/documents/SoybeanInoculation.pdf
Elmore, R. W. (1996). Soybean Inoculation—When is it
necessary?
Potter, B. (2004). Yield effects of seed applied
fungicide, insecticide and Rhizobium inoculants on soybean.
http://swroc.coafes.umn.edu/SWMNPEST/04publications/yieldeffects/innoculant.htm
Before you schedule your vacation this summer, make sure to get these two dates on your calendar. The 2006 MSU Weed Tour will be held on Wednesday, June 28 and the fourth annual MSU Crop Diagnostic Day will be held on Friday, July 21. These field days offer you the latest information in weed management and other crop protection and crop management strategies. Stay tuned to future Field Crop CAT Alerts for details and registration forms for each of these events.
Recent rains and warm weather coupled with some of the
earliest planted sugar beets in
Whether a grower chooses to use micro-rates or standard-split herbicide applications, scouting will be an important step in determining when this first herbicide application should be made. For a micro-rate program, the first micro-rate herbicide application should be made when the weeds are less than 1/8-inch tall. This normally occurs between 225 and 275 growing degree days, base temperature 34°F (GDD) after the last weed control measure was made (tillage or herbicide application at or around the time of planting). In some cases if sugar beets were planted during the last week of March or the first week of April we have accumulated anywhere from 160 to 300 GDD with the majority of the accumulated GDD occurring during the last two weeks. In some areas where beets were planted early there were hard frosts and the GDD clock may actually start later, because the frost would have controlled some of the early emerging weeds. Under these conditions you may want to start accumulating GDD at the time of that frost and then start scouting at 200 GDD.
For standard-split herbicide applications, the first application should be made when the weeds are 1/2-inch tall which will generally occur between 350 and 400 GDD. This is the time when growers should start scouting for that first standard-split application.
If a PRE herbicide was used in the field this could also impact the timing on when the first postemergence herbicide application needs to be made. There are several factors that may influence this timing including: method of application (banded or broadcast), susceptibility of the weeds to the PRE product or products that were used, and whether the grower is planning on using cultivation for weed control. All of these factors need to be accounted for when making that first postemergence application. For example, if a PRE herbicide was banded and cultivation will be used for between the row weed control and there are no weeds emerging in the band, the POST herbicide application can be delayed.
Taking all of this information into consideration after the first micro-rate herbicide application is made, there are some general guidelines for timing micro-rate herbicide applications using GDD. These recommendations are listed below.
After the first micro-rate application is made, MSU research
has shown applying micro-rates on a 225 GDD schedule has shown the most
consistent weed control across species while reducing the potential for sugar
beet injury. However, in fields with sandy or darker soils (high organic
matter) and high weed pressures, it is suggested to check fields at 150 GDD and
time applications for 175 GDD. For growers who want to adjust the timing of
micro-rates relative to weed emergence, it may be possible to lengthen the
spray interval early in the season (April) to 275 GDD when common lambsquarters
is the predominant weed. In May this interval should be shortened to 225 GDD
until pigweeds (redroot pigweed and Powell amaranth) start to emerge, then
micro-rate applications should be made every 175 to 200 GDD. If timing is
missed, it is important to scout to determine the size of the weeds out in the
field and reevaluate what the next weed management step should be.
There are several good calculators out there to help calculate GDD for scouting and for micro-rate herbicide applications. Michigan Sugar Company through the use of BeetCAST (http://www.michiganbeets.com) and the Michigan Automated Weather Network or MAWN (http://www.agweather.geo.msu.edu/mawn/) are two websites where there are excellent calculators to help determine GDD in the different sugar beet growing areas or you may choose to calculate your own.
GDD Formula = (High
Temp + Low Temp)/2 - 34°F
Establishing productive Roundup Ready (RR) alfalfa stands require close attention to details, especially when the plants are young. An early-season application of glyphosate will significantly help alfalfa establishment in two ways. First, glyphosate will remove many of the weed seedlings competing with the new alfalfa seedlings for nutrients and space. By targeting weeds when they are small, excellent control can be expected for almost all weed species.
The second reason for an early application of glyphosate in RR alfalfa is to remove the alfalfa seedlings that do not have the glyphosate-resistant trait. As new alfalfa stands mature, natural thinning takes place, which reduces the total number of alfalfa plants. As surviving plants grow, they fill empty spots in the crop canopy until a healthy, productive alfalfa stand is established (Figure 1). In a typical bag of RR alfalfa seed, a small portion of the seeds do not carry the glyphosate-resistant trait. These seeds will germinate and grow into plants indistinguishable from the glyphosate-resistant alfalfa plants. If an application of glyphosate is made, the non glyphosate-resistant plants will be controlled. By applying glyphosate early in the development of an alfalfa stand, the susceptible plants are removed, allowing the glyphosate-resistant plants to remain (Figure 2). Delaying the application of glyphosate will increase the chance of a non glyphosate-resistant alfalfa plant becoming an established plant in the alfalfa stand. When this occurs, the susceptible plant will suffer severe injury and/or death after the first application of glyphosate, leaving an empty spot in the stand (Figure 3). These open areas allow weeds to become established, possibly leading to reductions in yield and alfalfa quality.
MSU recommends
applying glyphosate at a rate of 0.75 lb ae/A before the 4th trifoliate
growth stage to eliminate seedlings not containing the glyphosate-resistant
gene. This practice encourages the development of a health population of RR
alfalfa plants and prevents susceptible plants from becoming established. When
making any pesticide application, always read and follow all the directions
found in the label.
There are
currently a large number of winter annual and perennial weeds present in
no-till corn and soybean fields. It is important to control these weeds prior
to crop emergence. These weeds may become very competitive if not controlled.
In some
cases, it may be desirable to control these weeds several days prior to
planting. With high weed density, excessive plant material can also interfere
with seed placement and may slow planting. Table 1G and Table 2C (both in the 2006 Weed Control Guide for Field Crops, E-434)
list rates and effectiveness ratings for burndown herbicides in no-till corn
and soybeans, respectively.
Once wheat has passed Feeke’s Stage 6, the risk of herbicide injury from 2,4-D, MCPA, Banvel/Clarity, or Curtail increases and application of these herbicides is not recommended. In this situation, the remaining herbicide options for broadleaf weed control are Harmony Extra, Harmony GT, Express, Buctril, Stinger and Starane. Harmony Extra, Harmony GT, Affinity BroadSpec and Express can be applied to wheat until the flag leaf is visible (before Feeke's Stage 8). Buctril, Stinger and Starane can be applied to wheat up to boot stage (before Feeke's Stage 9).
Each spring there are questions about the risks associated with 2,4-D or MCPA application to wheat past Feeke's Stage 6. Wheat tolerance of 2,4-D is highest between Feeke's stages 3 and 6 and is lowest in Feeke's Stages 9 and 10. Between stages 6 and 9, sensitivity to 2,4-D gradually increases as wheat growth stage advances. Thus, the risk of injury increases as wheat growth stage advances between stages 6 and 9. Severe injury is highly probable when 2,4-D is applied at Feeke's stages 9 and 10.
MSU recommends that application of 2,4-D to wheat be made after wheat has reached Feeke's stage 3 but prior to Feeke's stage 6. If growers choose to apply 2,4-D at later stages, they need to understand the associated risk. This risk can be minimized by applying the amine form of 2,4-D or reducing the rate of a 2,4-D ester. A much better alternative on wheat past Feeke's stage 6 is to use another broadleaf herbicide with a wider application window that is effective on the weeds present in the field.
Several growers have reported problems with grasses such as
cheatgrass, windgrass and annual bluegrass in their winter wheat. The control
options for grass control in winter wheat is limited. Osprey, Olympus 70% and
Everest are products labeled for use in
Liquid urea-ammonium nitrate fertilizer (28%N) is a common
carrier for herbicides in wheat. The most common herbicide to be used in this
manner is 2,4-D ester (2,4-D amine is difficult to mix in 28% N). Application
of herbicide in 28% liquid nitrogen can cause leaf burn from the nitrogen,
especially under hot, humid conditions. This risk increases with later wheat
growth stages because more leaf area is exposed to the treatment and recovery
time is shorter. In addition, the use of surfactant (required with herbicides
such as Harmony Extra) greatly increases leaf burn potential. MSU research has
demonstrated that excessive leaf burn from high nitrogen rates combined with
surfactant can reduce wheat yield. To minimize this risk:
§ Do not apply more than 20 lbs of nitrogen per acre in the form of 28% N when using a surfactant with herbicide.
§ Do not apply more than 40 lbs of nitrogen per acre in the form of 28 % N when no surfactant is used.
§ Avoid high-temperature, high-humidity days. Late afternoon applications carry less risk of leaf burn.
The use of postemergence
(POST) glyphosate in Roundup Ready soybeans has been the primary weed control program
used by many
One way to help overcome
some of these concerns is to implement the use of a soil-applied or
preemergence (PRE) herbicide into your soybean weed control program. Using a planned PRE residual herbicide
followed by a POST glyphosate application can result in more consistent weed
control, reduces the size and number of weeds present at the POST application
timing, and offers greater flexibility in the POST application window. One of the concerns that many producers have
in implementing a PRE herbicide is the economics. While a PRE herbicide may increase the cost
of your weed control program, resulting benefits often make up for the cost by
increasing weed control and yield. Below
are some of the benefits realized by PRE followed by POST weed control
programs.
Using a PRE herbicide
will control a number of weeds that would have emerged and competed with the
crop as it becomes established. While
early-season competition may not be a factor if the POST application is timed appropriately,
(remember that weeds can increase in size in a number of days and if you are
trying to spray a large number of acres or you become delayed in your
applications due to rain) early-season weed competition can become a problem. Remember, for timely POST applications to
avoid yield losses due to early-season weed competition, MSU recommends weeds
should be controlled before they are 4-inches in height in 7.5- and 15-inch
rows and 6-inches in height in 30-inch rows.
Several weed species
have continual emergence or emerge only later in the season. These species can include: annual grasses,
giant ragweed (
In
Control of perennial
weeds is more effective in the later stages of growth (bud to flower
stage). Because PRE residual herbicides
will provide initial control of annual weeds the POST glyphosate application
may correspond more appropriately to the stage of growth needed for perennial
weed control.
One possible long-term
benefit from including a PRE herbicide in your weed control program is the
implementation of herbicide resistance management strategies. A PRE herbicide would include another mode of
action into the weed management program and reduce the number of weeds present
for the POST application. Ultimately,
these two benefits will relieve the selection pressure of a glyphosate-only
weed management system.
A Section 18 label for
Pre-harvest and pesticide application reentry information will be on the label.
Nitrogen fertilizers are expensive and may become unavailable to your crop. Because of this, corn producers will need to manage nitrogen fertilizer carefully to remain profitable in 2006. Listed below are some strategies for getting the most from your investment in nitrogen fertilizer.
Studies have shown that only 40 to 60% of the nitrogen you apply is taken up by your crop. Another 20 to 30% remains in the soil after harvest and 10 to 20% becomes unavailable to plants during the growing season. The losses are due to three processes, volatilization, leaching and denitrification. Volatilization occurs when fertilizers containing urea undergo rapid hydrolysis in the soil. Significant losses of ammonia gas can occur. Nitrate-nitrogen is susceptible to losses from leaching and denitrification. Leaching is most likely to take place in coarse-textured soils. Denitrification of nitrate-nitrogen occurs under saturated conditions on fine-textured soils. Over 100 lbs. of nitrogen per acre can be lost from denitrification in five days under the proper conditions.
The three main nitrogen fertilizer sources are anhydrous ammonia, urea and urea ammonium nitrate solutions (UAN). Anhydrous ammonia is still the least expensive form of nitrogen. It must be injected 6 to 8 inches deep and the slot must be sealed to prevent losses. If applied properly, it is the most stable nitrogen source as it is the slowest fertilizer to be converted to nitrate. Urea is subject to volatilization losses. Volatilization occurs rapidly under warm air temperatures in fields having low CEC’s, heavy residues and adequate moisture. These losses can be reduced by incorporating the fertilizer with tillage at least 1 to 3/4 inches deep or by at least 3/4 of an inch of irrigation or rain fall. Urease inhibitors are available to mix with the fertilizer and prevent volatilization for 10 to 14 days following a surface application. The urea will not be available to plants during this time. UAN solutions are comprised of half urea and half ammonium nitrate. Therefore, half of the nitrogen is subject to volatilization losses. About 25% percent of the nitrogen is in the nitrate form at the time of application and is subject to losses from leaching or denitrification.
The first step is to determine your price per pound of actual nitrogen and the market price you expect to receive for your corn. Determine the corn to nitrogen price ratio from Table 1. Next you will need to set realistic yield goals for your fields. A realistic yield goal is the average yield you attained in the field for the last five production years for that crop. Find the point on Table 2 where your yield goal and your corn to nitrogen price ratio intersect. You may have to interpolate between rows and columns. This is the most economical nitrogen rate for this field.
|
N cost ($/lb) |
Corn Price ($/bu) |
||||||
|
1.00 |
1.50 |
2.00 |
2.50 |
3.00 |
3.50 |
4.00 |
|
|
|
---corn:N price ratio--- |
||||||
|
.10 |
10:1 |
15:1 |
20:1 |
25:1 |
30:1 |
35:1 |
40:1 |
|
.15 |
7:1 |
10:1 |
13:1 |
17:1 |
20:1 |
23:1 |
27:1 |
|
.20 |
5:1 |
8:1 |
10:1 |
12:1 |
15:1 |
18:1 |
20:1 |
|
.25 |
4:1 |
6:1 |
8:1 |
10:1 |
12:1 |
14:1 |
16:1 |
|
.30 |
3:1 |
5:1 |
7:1 |
8:1 |
10:1 |
12:1 |
13:1 |
|
.35 |
3:1 |
4:1 |
6:1 |
7:1 |
9:1 |
10:1 |
11:1 |
|
.40 |
2:1 |
4:1 |
5:1 |
6:1 |
8:1 |
8:1 |
10:1 |
|
.45 |
2:1 |
3:1 |
4:1 |
5:1 |
7:1 |
8:1 |
9:1 |
|
.50 |
2:1 |
3:1 |
4:1 |
5:1 |
6:1 |
7:1 |
8:1 |
|
Source: MSU Extension Bulletin
E-802 |
|||||||
|
Corn:N Price ratio |
Yield potential of soil (bu/A) |
||||||||||||||
|
85 |
100 |
115 |
130 |
145 |
160 |
175 |
190 |
||||||||
|
|
- - -most profitable N rate (lb N/A)- - - |
||||||||||||||
|
4:1 |
70 |
80 |
100 |
110 |
120 |
130 |
140 |
150 |
|||||||
|
5:1 |
80 |
90 |
100 |
110 |
130 |
140 |
150 |
170 |
|||||||
|
7.5:1 |
85 |
100 |
115 |
125 |
145 |
160 |
170 |
190 |
|||||||
|
10:1 |
90 |
110 |
130 |
140 |
160 |
180 |
190 |
210 |
|||||||
|
15:1 |
100 |
120 |
140 |
160 |
180 |
200 |
220 |
240 |
|||||||
Corn growers can reduce their nitrogen fertilizer application rates by taking credit for the nitrogen contributions from legumes, manure applications and the soil. The credits should be subtracted from the most economical nitrogen rate determined above. Soybeans will contribute 30 pounds of actual nitrogen to the following corn crop. Established alfalfa and clovers will contribute between 40 and 90 pounds of actual nitrogen, depending on the plant population. Manure can be an excellent source of nitrogen. The pre-sidedress nitrate test is a proven method for determining the nitrogen contributions from manured and non-manured fields. Do not take nitrogen credits when growing wheat. Wheat’s peak demand for nitrogen occurs earlier in the growing season before organic nitrogen has been converted to plant available forms.
|
PSNT Credit(lbs./acre) |
Cost Savings on Nitrogen ($/acre) |
Economic Gain($/acre) |
|
30 |
8.70 |
5.70 |
|
60 |
17.40 |
14.40 |
|
90 |
26.10 |
23.10 |
|
120 |
34.80 |
31.80 |
|
Source: Dr. Carrie Laboski Sampling and analysis costs are $3/acre |
||
Always apply at least 20 pounds of actual nitrogen per acre in a 2 x 2 band at planting time. Increase this amount to 30 to 40 pounds per acre when planting into heavy residues. Ideally, the rest of your nitrogen should be applied in early June as this coincides with the beginning of the crop’s peak demand for nitrogen. By applying most of your nitrogen in June, you will significantly reduce the potential for nitrogen losses due to leaching and denitrification. If you must apply your nitrogen prior to planting, consider using a nitrification inhibitor. These products can delay the conversion of ammonium to nitrate by 4 to 10 weeks. Nitrification inhibitors will work best if the nitrogen fertilizer rate is slightly deficient. Please see Table 4 to determine the probability of realizing an economic return from nitrification inhibitor