High Value Straw and Weedy Wheat…What Do I Do?

Wet fields, thin stands and spotty winter-kill made spring weed control difficult to impossible in many winter wheat fields, and prolonged wet conditions have encouraged prolific weed growth from competitive broadleaf weeds like giant ragweed and lambsquarters. As we approach harvest in southern WI (week of July 21st) growers simply have limited herbicide options for preharvest weed management. The most popular ones are:

  1. 2,4-D products. There is a 14 day pre-harvest interval with this product. Pre-harvest treatment can be applied when grain is in the dough stage. Only one preharvest application per crop cycle allowed and a maximum of 0.5 lb 2,4-D acid equivalent per acre per application. Please read label for specific product used as there are differences among labels.
  2. Glyphosate products. There is also a 7 day pre-harvest interval with this product, and it can NOT be applied until the grain is at the hard-dough stage (30% moisture or less). Grain treated with glyphosate at this growth stage should not be used for seed as germination can be significantly lowered. Maximum of 0.77 lb glyphosate acid equivalent per acre per application (equivalent of 22 fl oz of Roundup PowerMax per acre).

Some benefits to applying preharvest 2,4-d or glyphosate may include desiccation of green weedy plants to enable an easier combine harvest and quicken the ability to bale straw following the grain harvest. However, drawbacks include a narrow window of application timing ahead of harvest, wheel tracks (if ground applied) will reduce grain yields, and moreover many of the weeds like giant ragweed, waterhemp and lambsquarters will be large and difficult to control. Drift is also a concern when spraying crops this late in the season, particularly with synthetic auxin herbicides such as 2,4-D. Thus, consider a preharvest 2,4-d or glyphosate application as a last resource because partial control of large weeds will greatly increase selection pressure for herbicide resistance. We already have several issues of herbicide resistance in Wisconsin (http://www.wiscweeds.info/post/herbicide-resistance-in-wisconsin-an-overview/).

Shawn P Conley and Rodrigo Werle

A Tank Full of Sugar Helps the Profits Go Down

Adapted from original article written 6/1/2015.

This growing season has been what I can best describe as “Craptacular“. Farmers are under severe economic stress and are looking to squeeze the highest yields possible out of whatever acres they were able to get planted. Across the Midwest post emergence herbicide applications are going out and farmers are considering what else to add into the tank to “help” their crops. This year the question of sugar has resurfaced so I thought I would dust off and re-post the below article originally entitled “Do Foliar Applications of Sugar Improve Soybean Yield”.

I also wanted to link to a few other articles from colleagues at the University of Nebraska “Sugar Applications to Crops – Nebraska On-Farm Research Network Results” and “Research Results: Sugar Applications to Crops“. In short the University of Nebraska team did not find a consistent yield increase in corn or sorghum and averaged 0.8 bu per acre in soybean. If farmers are considering a pass for just the sugar application the average cost of ground application in $7.65 and aerial is $10.75; 2019 Iowa Farm Custom Rate Survey and the average yield loss caused by sprayer wheel track damage in soybean in rows less than 20 inches is 1.9 or 1.3% with a 90 or 120 foot boom, respectively.

I also want to give credit to my colleague Chad Lee who wrote a nice article entitled “Could Sugar Help Drought Stressed Corn?” that discusses sugar rates, biological activity and actual costs of product.

I am certain this re-posted article will stir up the same severe indignation as the original, however when the local cash bids are averaging $8.42 ROI is more important than ever.

Do Foliar Applications of Sugar Improve Soybean Yield (Originally published: June 14th, 2011)

High commodity prices have led growers to consider many novel soybean inputs. One input that has garnered considerable attention is the foliar application of sugar products to increase soybean yield. The objective of this research was to evaluate soybean yield in response to various sources of foliar-applied sugar across four states in the Midwest. Field research studies were conducted at Arlington, Wisconsin; Urbana, Illinois; St. Paul, Minnesota; and West Lafayette, Indiana in 2010.The four sources of sugar evaluated in this study were:

  1. Granulated cane sugar
  2. High fructose corn syrup
  3. Molasses
  4. Blackstrap molasses.

All treatments were applied at the equivalent rate of 3 lb sugar a-1 and applied at 15 to 20 gal a-1. The treatments consisted of an untreated check, all four sources of sugar applied at V4, granulated cane sugar and blackstrap molasses applied at R1, granulated cane sugar applied at V4 and R1, and blackstrap molasses applied at V4 and R1.

No positive or negative (phytotoxic) effects were visually observed on the soybean foliage at any location within 10 days following foliar applications (data not shown). Furthermore, sugar did not increase soybean yield within location (data no shown) or across locations [P= 0.60 (Figure 1)], regardless of source. While this study cannot conclusively prove foliar applications of sugar will not increase soybean yield, the authors conclude that other management strategies to improve soybean yield should take precedence over applying sugar.


The source of this data is:

Furseth, B. J., Davis, V., Naeve, S., Casteel, S., and Conley, S. P. 2011. Soybean Seed Yield Was Not Influenced by Foliar Applications of Sugar. Crop Management. Accepted: 6/1/11.

Please visit: http://www.plantmanagementnetwork.org/sub/cm/brief/2011/sugar/ to view the entire manuscript.

Soybean and Corn are Considered Cover Crop Options in WI

Article written by Shawn P. Conley, Joe Lauer and Paul Mitchell

Today Joe Lauer and myself had the opportunity to travel to Door County and participate in an Extension meeting hosted by Annie Deutsch, Jamie Patton and Aerica Bjurstrom. We had great conversation with the group about the agronomic implications of the 2019 growing season. During this meeting we touched on the issues regarding prevent plant and what to do next. This is a obviously a complex issue but an interesting point was brought forward by Dan Muhlenbeck a crop insurance specialist… “Is soybean and/or corn considered a cover crop in WI?”  (I hope you all notice that in my blogs soybean always precedes corn..) Here are our thoughts.

For a crop to be considered a cover crop RMA states that “For crop insurance purposes, a cover crop is a crop generally recognized by agricultural experts as agronomically sound for the area for erosion control or other purposes related to conservation or soil improvement.” Soybean and corn both meet this requirement. However please remember that BMP’s must be followed to meet this requirement.

In a late planted, soybean cover crop situation, plant a minimum of 150,000 seeds per acre and strive to plant in narrow row spacings (<30 inches). This recommendation is intended to minimize soil erosion, maximize ground cover and weed suppression as well as provide adequate N fixation. I do however understand if a farm operation is limited by equipment restrictions (e.g. they only have a 30 inch row planter) I would not preclude them from being eligible to plant soybean as a cover crop. The next consideration is cost. Normally the cost of soybean seed to be used as a cover crop on a per acre basis would be cost prohibitive; however since soybean seed is usually not saved from year to year and treated seed is often devitalized it is often offered at a deep discount late in the year so shop around. Frankly with only 60% of the WI crop planted there should be some reasonably priced seed to be used as cover crops.Now lets talk about corn!

Although corn is not usually considered a cover crop due to 30-inch row spacing and slower early canopy growth than other crops, it is deep-rooted and by the end of the end of the growing season can produce more than 5 Tons DM/A of stover even when planted in July. Ultimately the decision to use corn as a cover crop is the cost of production. Typically, it would cost $400 to $450 per acre to establish corn. Production costs can be reduced by using seed that is not bioengineered, reducing N fertilizer to around 40 to 60 lb N/A, and using a narrower row corn planter (<30-inches), a twin-row planter, or grain drill to narrow row-spacing.

To be clear the intent of this article is to designate that soybean or corn can be considered as options for cover crops. The first thing you must do however is talk to your crop insurance agent and make no decisions without their input. Also please review this excellent article by Paul Mitchell entitled: Can I Use Corn or Soybeans as a Cover Crop on Prevented Plant Acres?

Farmers taking the full prevented plant indemnity should note that they cannot ever harvest the cover crop for grain or seed. RMA rules allow, only after September 1, grazing and harvest as hay (for bedding or feed) and now for silage, haylage or baleage. If a farmer wants to harvest it as grain or seed, then they should declare it as an alternative crop and only collected the partial (35%) prevented plant indemnity.”

With the aforementioned change to prevent plant indemnity the question of soybean as a forage popped into my mailbox multiple times today. From an agronomic perspective I think there are better forage options (higher tonnage) than soybean, but if this is an option for your farm here are some simple thoughts. Harvesting soybeans for forage between the R1 and R5 stage will result in a very high quality silage, but dry matter yields will be reduced significantly. Forage quality will be reduced from R5 soybean forward if a conditioning process is used during harvest as conditioning will cause significant seed shattering. According to our data early maturity group soybeans planted 6/20ish will likely already be at the R6/R7 stage so if you are intending to shoot for higher quality soybean forage go with a later maturity group soybean (~4.0).

Figure 1. Pooled Arlington and Hancock Data.

Figure 2. Spooner data.


This is a dynamic discussion so please check back as text and recommendations are subject to change as “to be frank” no one really has all the answers on this topic.

Soybean Flowers, Herbicide Labels, and Wheel Track Damage…Oh My!

Authored by Shawn P. Conley and Rodrigo Werle

We are starting to get the first reports of soybean beginning to flower (R1) in our early planted situations. As we enter the soybean reproductive growth phase there are a few things to keep in mind. The first is that soybean will produce flowers for ~3 to five weeks, depending upon planting date and environment. During that time soybean will abort anywhere from 20 to 80% of the flowers that they produce. Generally it is the first and last flush of flowers produced that are most likely to be aborted.

R1 soybean growth stage

Next, the timing window for many POST-emergence herbicide applications in our early planted soybean are quickly closing if not closed already. Glyphosate labels indicate that applications can be made through R2 or full flower, however the spread of glyphosate-resistant waterhemp and other weeds across Wisconsin and beyond has led several farmers to adopt soybean varieties containing the novel herbicide resistance traits (Xtend [which confers resistance to glyphosate and dicamba], Enlist E3 [glyphosate, glufosinate and 2,4-D] or LibertyLink GT27 [glyphosate and glufosinate]), which all provide effective herbicide options for POST-emergence broadleaf weed control. The application window for the POST-emergence herbicides associated with the aforementioned traits is also linked to soybean reproductive growth stages.

In Xtend systems, the registered dicamba herbicides Engenia, FeXapan and XtendiMax can be applied through 45 days after planting or up until R1 (first bloom; in other words, don’t apply if the soybeans are flowering), whichever comes first.

In LibertyLink systems (LL, LLGT27 or Enlist E3), glufosinate herbicides such as Liberty, Scout, Interline, etc. can be applied up to bloom or R1 growth stage (don’t apply if the soybeans are at R2 stage or advanced).

In Enlist E3 systems, the registered 2,4-D herbicides Enlist One and Enlist Duo should be applied no later than R2 or full flowering stage.

When deciding the best time for a POST application, target small weeds, follow all label requirements and don’t spray under adverse environmental conditions.

Soybean developmental note: on average it takes ~ 4 days to move from R1 (beginning flower) to R2 (full flower) and ~10 days from R2 to the start of R3 (beginning pod).

Last but not least, wheel track damage made from ground applications may start to reduce yield. Sprayer wheel traffic from first flower (R1) through harvest can damage soybean plants and reduce yield (Hanna et al. 2008). Our research suggests that an adequate soybean stand (more than 100,000 plants per acre) planted in late April though mid-May can compensate for wheel tracks made when a field is sprayed at R1. Yield loss can occur, however, when wheel tracks are made at R1 or later in thin soybean stands (less than 100,000 plants per acre) or late planted soybeans. Regardless of stand, plants could not compensate for wheel tracks made at R3 (early pod development) or R5 (early seed development). The average yield loss per acre is based on sprayer boom width (distance between wheel track passes). In our trials yield losses averaged 2.5, 1.9, and 1.3% when sprayer boom widths measured 60, 90, and 120 foot, respectively. Multiple trips along the same wheel tracks did not increase yield loss over the first trip.

Spraying soybean at the R1 crop growth stage
Wheel track damage to drilled soybean at R1

Hanna, S., Conley, S. P., Shaner, G., and Santini, J.  2008.  Fungicide application timing and row spacing effect on soybean canopy penetration and grain yield.  Agronomy Journal: 100:1488-1492.

Are Your Beans “Feelin the Burn”?

Adapted from original article posted 6/10/2018 by Shawn P. Conley and Damon Smith

Weed management has been a significant challenge for many farmers and retailers in 2019. The challenges range from short planting windows to shorter pre-emergence and post emergence herbicide application windows to early soybean flowering. As we approach the end of growth stage cutoffs for herbicide applications in early planted soybean can we expect any damage from herbicides and especially the Group 14 herbicides? Well unfortunately the answer to that question is the good ole Extension cop-out answer “Well folks that depends“…..

What we mean by that is as follows:

  1. What growth stage was the soybean crop at?
  2. Where in the United States are you located?
  3. Was the crop stressed before or more importantly after the application?
  4. What rate, a.i., adjuvants, carriers, tank mix partner, etc are we dealing with?
  5. What soybean variety did you plant?
  6. What phase is the moon in….well not really… but you all get the point.

Generally speaking as the soybean growth stage approaches R1 (flowering) the risk for yield loss increases. However this is a highly regional response as we have documented differential yield responses from a +1.2% yield gain in the south to a -4.7% to -4.1% yield loss from the I-states north (Table 1). Furthermore as we transition from specifically using lactofen as a “herbicide” to a tool in white mold management we also note a differential response.  In a recent meta-analysis where Dr. Smith focused on the 6 oz lactofen rate at R1 application he noted a 3.7% yield loss in low-to-moderate disease pressure, but a significant yield increase in high-pressure situations (Figure 1). In Dr. Smith’s meta-anlaysis he does want to emphasize they noticed A LOT of variability among varieties and environments tested  as you can see by the error bars around treatments in Figure 1.

In summary we would expect some level of yield loss in these late “hot” applications; however in-terms of long-term weed management we would rather see you take a small yield hit than allow herbicide resistant weeds go back to seed and replenish the weed seed bank. This is even more critical with expected tighter phytosanitory regulations centered around weed seeds.

Table 1. Percent relative yield change and break-even probabilities for Lactofen applications (12 fl. oz per a + 1%v/v COC) at V4 soybean compared to no application at multiple yield levels and soybean sale prices for studies be­tween 2012 and 2014.


Yield level


45 bu a-1

60 bu a-1

75 bu a-1

Region RYC (%)










——————-% probability of break-even——————-
























-4.1 0 0 0 0 0 0 0 0


†RYC, percent relative yield change compared to the standard practice
South: Arkansas, Kansas, Kentucky

I-States: Indiana, Iowa, Illinois

North: Michigan, Minnesota, Wisconsin

Figure 1. Yield response to white mold management by disease pressure.

Literature cited:

J.M. Orlowski, B.J. Haverkamp, R.G. Laurenz, D.A. Marburger, E.W. Wilson, S.N. Casteel, S.P. Conley, S.L. Naeve, E.D. Nafziger, K.L. Roozeboom, W.J. Ross, K.D. Thelen, and C.D. Lee. 2016. High-input soybean management systems affect soybean yield, yield components, and economic break-even probabilities. Crop Sci. 56: 4: 1988-2004. doi:10.2135/cropsci2015.10.0620.

Willbur, J.F., Mitchell, P.D., Fall, M.L., Byrne, A.M., Chapman, S.A., Floyd, C.M., Bradley, C.A., Ames, K.A., Chilvers, M.I., Kleczewski, N.M., Malvick, D.K., Mueller, B.D., Mueller, D.S., Kabbage, M., Conley, S.P., and Smith, D.L. 2019. Meta-analytic and economic approaches for evaluation of pesticide impact on Sclerotinia stem rot control and soybean yield in the North Central U.S. Phytopathology. https://doi.org/10.1094/PHYTO-08-18-0289-R.

Soybean Replant Decisions: Just the Facts Jack!

Though farmers continue to struggle to get their crops established in #plant19 we are starting to see the first images of soybean beginning to crack and emerge. As farmers, agronomists and technical service providers begin to assess the 2019 soybean stands here are a few items to contemplate before re-plant recommendations are made.

  1. Get an accurate stand assessment. We are often drawn to the worst areas of fields and over-blow how bad the overall stand really is. You can go old school and use the tape or hula-hoop method or try a digital approach such as Bean Cam the WSMB funded soybean replant app!
    1. Link to the app store for iPhone and iPad
    2. Link to the app store for Android

      Bean Cam app calculations/results.

  2. An effective stand is obviously important to maximize soybean seed yield. However the downside yield risk for a sub-par stand is minimal until stands fall below 50,000 plants per acre. The synergy of early planting coupled with breeders adding 3x yield to soybean branches at low populations have effectively reduced the yield penalty for thins stands by 1/2 (Suhre et al. 2014) . Therefore we recommend the following.
    • Early planted soybean yield is maximized with stands that range from 100,000 (high yield environment) to 135,000+ (low yield environment) plants per acre.
    • When soybean stands are less than 50,000k plants per acre, inter-plant new seed with a similar maturity into the existing stand. DO NOT TEAR UP THE STAND AND START OVER.
    • When stands fall between optimal and 50,000k plants per acre Think Twice Before Replanting Soybeans! Our data shows a nominal ~2 bu yield increase in this situation. Even if you have a “free replant” guarantee the numbers don’t make economic sense. As a grower you are better off investing $$$ in an effective in-season residual herbicide to control weeds such as Palmer and waterhemp.


Gaspar, A. and S.P. Conley. 2015. Responses of canopy reflectance, light interception and soybean seed yield to replanting sub-optimum stands. Crop Sci.55: 377-385. doi: 10.2135/cropsci2014.03.0200

Suhre, J.J., Weidenbenner, N., ‡Rowntree, S., Wilson, E., S., Naeve, S. Casteel, S.P. Conley, Diers, B., Esker, P., Specht, J., and Davis, V. 2014. Soybean Yield Partitioning Changes Revealed by Genetic Gain and Seeding Rate Interactions. Agron. J. 106:1631–1642.

First thoughts on managing your prevent plant acres

I want to start out this blog being very clear and honest…… I don’t exactly know what the right answer is! However as I have stated before, the best thing about blog articles is that it is a dynamic format and can be rapidly updated and changed. I am sure this blog article will change weekly (maybe daily) as we learn more and I get feedback on this article. So let’s get into it. I think we all agree we need to put something on these fields to not only hold the soil but also manage our weed populations, especially waterhemp. To that end I had two farmers call me this week and ask what would happen if they planted winter rye in June. That is a good question I said so I reached out to many colleagues and we all agreed that yes that was a good question, but none of us had done it to date. Our collective thought was that winter rye or winter wheat (I think rye would be better) would grow 18″ up to maybe 4′ tall, stool out and put out multiple tillers since the plant will not vernalize and induce reproduction. This should develop a fairly rapid and robust canopy that can be very competitive with weeds. Speaking with Fred Kolb at UI, he thought that oat would also be a good cover as it would develop well put out seed heads, and if worked into the soil in the fall, reseed the system and then winterkill so you wouldn’t need to worry about termination next spring. For all of these crops I would target 750,000 to 1,000,000 seeds per acre as a seeding rate (WAG). Obviously this is not a perfect system as there may be some herbicide carryover issues from last year’s crops and we would be planting 100’s to 1000’s of acres that may serve as a green bridge for plant pathogens, but that is potentially next years problems. I encourage anyone reading this article to send me thoughts, feedback or other ideas. I am sure someone has tried this and I would like to add in your experiences.

Adjust Your Seeding Rate (Higher) But Not Your Maturity Group For Late May Planted Soybean

Adapted from original article written in 2018 by Authors: S.P.Conley, J.M Gaska, S. Mourtiznis, D. Mueller, and A. Varenhorst

With only 11 days left in May and roughly only 19% of the Midwestern soybean crop planted (WI:12%, IA:27%, SD:4%) what if any production changes should growers consider modifying?

  1. Do Not Switch Your Maturity Group….Yet: Do not consider switching to an earlier soybean maturity group until ~June 1. After June 1 do not go any earlier than a 0.5 MG earlier variety. For more information please see:  Soybean Planting Date and Maturity Group Considerations Moving into 2019.
  2. Increase your seeding rate to roughly 154,000 seeds per acre. Efficacy of soybean seed-applied fungicide and insecticide at early and late planting dates and a range of seeding rates were tested in multiple states during the 2016 and 2017 growing seasons. Researchers in Iowa, South Dakota, and Wisconsin participated with 4 locations each year for a total of 24 location/years.  Seed treatments included a) UTC, b) fungicide (prothioconazole, penflufen, and metalaxyl), and c) fungicide+insecticide (clothianidin). Only late planting dates were used in this below analysis. The average of the late planting dates for each state over the two years were: IA: May 24,  SD: June 21, and WI: May 31.  Seeding rates were in increments of 20,000 from 60,000 to 160,000 seeds/acre. There was a quadratic yield response to seeding rate that was significant (Figure 1). Maximum yield was observed at 154,000 seeds/acre. The curve is not very steep which shows that practical yield differences between seeding rates were not large. So, the curve does not tell the whole story. We re-ran the model with seeding rate as a categorical variable. The results suggest that yields for 140 and 160K were not different and 100-140K were not different either (Table 1). It may be argued that our seeding rate was not extended high enough…I assume my Twitter “friends” will come back and say “hey bean boy why didn’t you go to 180 or 220,000 seeds per acre”. That is a valid critique however given the flat response curve we find it difficult to believe we would have seen a significant yield response above where we are. As a reminder our recommended seeding rate for early planted soybean can be found here: The Soybean Seeding Rate Conundrum.
  3. Interpret the below information on return above seed cost cautiously. The best part of writing in a blog format is that you get to tweak the post after it is originally published. To that point we had several comments last year on the the small yield response difference between seeding rates and question the optimal farmer return above seed cost. If you were to look only at that factor the optimal seeding rate would be ~100,000 seeds per acre even at a late May planting (Table 2). Though those economic numbers are very appealing I would caution growers to not go this low if they have uneven or rocky fields as harvestabilty will be a challenge with a lower soybean pod set. Furthermore many soybeans will be “planted” and I use that term loosely into unfavorable environments (cold, wet and compacted soils) and emergence issues will be likely. I would also not go this low in fields that are prone to drought as the rows will be slower to canopy and lead to greater soil water evaporation and subsequent weed competition. This leads us to waterhemp and its wonderful biology of delayed germination and prolific seed set. The point I am trying to make is this is a system and as Paul Harvey so eloquently stated……”now for the rest of the story”!
  4. Figure 1. Soybean seed yield response to seeding rate for soybean planted in Late May and June in IA, WI, and SD.

Table 1. Mean soybean seed yield response to seeding rate for soybean planted in Late May and June in IA, WI, and SD.

Soybean seeding rate

(1000 seeds per acre)

Soybean Seed Yield

(bu per acre)

160 67.3 A
140 66.6 AB
120 66.0 B
100 65.8 B
80 63.8 C
60 61.6 D
Tukey-Kramer Least Squares Means (Alpha=0.05); LS-means with the same letter are not significantly different.

Table 2. Return above seed cost at various market prices for seeding rates over 60000 seeds/acre.

Seeding rate


Yield difference compared to 60000 seeds/a

Soybean market price ($/bu)









——– ——– $/acre —————







6.11 7.21 8.31 9.41 10.51



10.83 12.93 15.03 17.13 19.23



2.94 5.14 7.34 9.54 11.74



-2.14 0.36 2.86 5.36 7.86



-6.53 -3.68 -0.83 2.02 4.87
Based on $65.00/140000 seeds