Are Your Beans “Feelin the Burn”?

Shawn P. Conley and Damon Smith

Weed management has been a significant challenge for many farmers and retailers in 2018. 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 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 potential Chinese tariffs and 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 (%)

$9

$12

$15

$9

$12

$15

$9

$12

$15

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

South

1.2

31

47

57

47

60

67

57

67

72

I-states

-4.7

0

0

0

0

0

0

0

0

0

North

-4.1 0 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., P. Mitchell, M. Fall, A. Byrne, S. Chapman, C. Floyd, C. Bradley, K. Ames, M. Chilvers, N. Kleczewski, D. Malvick, B. Mueller, D. Mueller, M. Kabbage, S.P. Conley, D.L. Smith. 2018.  Meta-analytic and economic approaches for evaluation of fungicide impact on Sclerotinia stem rot and soybean yield in the North Central U.S. PhytoPatholgy. In review

The Soybean Flowering – Summer Solstice Fallacy

Shawn P. Conley, Lindsay Chamberlain and James Specht

Every agronomist has been ingrained with the Nowledge that soybean is considered a “short-day” plant and will not flower until after June 21st a.k.a. the summer solstice. This belief has held true for decades; however, with agronomists now preaching the virtues of early soybean planting, coupled with the power of Twitter, we now see pictures and evidence of soybean flowers occurring as early as June 1. This empirical evidence has prompted many to question the foundational belief.

In soybean, floral induction occurs when soybean leaves can measure the night length (from dusk to dawn), and thus begins when unifoliolate leaflets appear at stem node 1 (V0) and a young trifoliolate leaf appears at node 2, with induction continuing thereafter in every subsequent leaf (Wilkerson et al. 1989; Fehr and Caviness, 1977). If soybean is planted early enough, flower initiation can then be triggered on the front of the summer solstice (Figure 1). This response is dependent upon the maturity genes present in the adapted cultivars and region of country, however given the germplasm available to farmers in the north central region it is plausible that any soybean planted in this region would flower “early” if planted early.

In 2018 we have experienced exceptionally warm temperatures after V1 that have significantly hastened the calendar date of R1, because the temperature sensitivity of floral evocation (development of floral meristems into flowers – the first such visible flower leading to an R1 stage call), though floral induction in itself is not very temperature sensitive.  In NE in 2017, the website program SoyWater (SoySim) predicted that an Apr 24 planting date would lead to the R1 stage dates for MGs 1, 2, 3, & 4 to occur on Jun 12, 14, 17, & 19; however, this year (2018), SoyWater (SoySim) is predicting for the same planting date of Apr 24 and near similar MGs, R1 stage dates of June 05, 10, 13, & 16!  Those R1 stage predictions were (as Dr. Specht recall) 3-5 days later a couple of weeks ago, so not only a warm spring, but also this exceptional heat wave in the last few days has hastened floral evocation.  R1 is likely to be earlier in all NC USA areas that have experienced both early soybean planting and a much warmer than normal spring. Early soybean flowering has many management implications including shorter herbicide label timings for dicamba (up to R2) and glyphosate products (through R2) (FYI it usually only takes 3-5 days to go from R1 to R2) and earlier risk for white mold infection. In 2018 it is paramount that you scout and don’t just rely on the calendar for spray applications!

Figure 1. Planting date by day length hours in Lincoln NE.

Literature cited:

Fehr, W.R., Caviness, C.E., 1977. Stages of soybean development. Cooperative Extension Service, Agriculture and Home Economics Experiment Station, Iowa State University, Ames, Iowa.

G, G. Wilkerson,* J. W. Jones, K. J. Boote, and G. S. Buol. 1989. Photoperiodically Sensitive Interval in Time to Flower of Soybean. Crop Sci. 29:721-726.

Variable Germination and Emergence in Soybean: Which Seeds Are Still Viable?

Many of us, including myself, have planted under less than ideal soil conditions this spring.  Often the ground was worked a little on the wet side leading to clods and variable seeding depths for our soybean crop.  Reports of variable and delayed emergence in conventional (more common) and no-till soybean is raising replant and seed viability questions in several areas across the Midwest.  If soybean was planted into dry soil and had not imbibed water (seed did not swell) then there is little to no concern for growers.  Once a significant rainfall event occurs, the soybean will imbibe water, germinate, and should emerge normally.  For yield estimates, we would assign the day it rained as the new planting date.

The more difficult question to answer is “How viable is the soybean seed once imbibition and/or germination has begun?”  The critical seed moisture content for soybean germination is 20%.  A soybean seed that has imbibed water, has a split seed coat, or has an emerged radicle will continue to germinate and grow as normal once the seed is re-hydrated if the seed (embryo) remains above 20% moisture (Senaratna and McKersie, 1983) (Image 1).

Image 1. Soybean germination

If the moisture content within a soybean seed falls to 10% due to dry conditions after germination has started, then a dramatic difference exists among the different seed germination stages.  If the seed has imbibed water for 6 hours (seed is swollen, but the seed coat has not broken), then the seed is dehydrated to 10% moisture, germination is not affected.  If the seed has imbibed water for 12 to 24 hours (seed coat broken, but prior to radicle emergence), then germination is reduced to 60 to 65%.  If the radicle has emerged and seed moisture levels drop to 10%, then no survivors can be expected (Image 2).

Image 2. Variation in soybean imbibition

To test seed viability, growers can conduct a simple germination test.  First excavate 100 soybean seeds and wrap them in a damp paper towel.  Place these seeds in a warm location, and after 24 to 36 hours, count the number of seeds that have germinated (Image 2).  Remember that a typical soybean germination is 90% (Image 3).

Image 3. Soybean germination roll test

Literature Cited:

Senaratna, T. and B. D. McKersie.  1983.  Dehydration Injury in Germinating Soybean (Glycine max L. Merr.) Seeds.  Plant Physiology 72: 620-624.

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

Authors: S.P.Conley, J.M Gaska, S. Mourtiznis, D. Mueller, A. Varenhorst

With only 10 days left in May and roughly 50% of the Midwestern soybean crop planted (WI:33%, IA:58%, SD:24%) 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 2018
  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 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 published. To that point we have had several comment 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 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. 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

Yield difference compared to 60000 seeds/a

Soybean market price ($/bu)

9.00

9.25

9.50

9.75

10.00

seeds/a

bu/a

—–bu/a—–

——– ——– $/acre —————

60000

61.6

Base

80000

63.8

2.2

11

11

12

12

13

100000

65.8

4.2

19

21

22

23

24

120000

66.0

4.4

11

12

14

15

16

140000

66.6

5.0

8

9

10

12

13

160000

67.3

5.7

5

6

8

9

11

Based on $65.00/140000 seeds

Soybean Replant Decisions: Just the Facts Jack!

The Twittersphere is erupting with pictures of soybean beginning to crack and emerge. As we finalize #plant18 and start to assess our soybean stands here are a few items to contemplate.

  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.

References:

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.

Soybean Management Strategies to Facilitate Timely Winter Wheat Establishment in 2018

Article written by Dr. Adam Gaspar and Dr. Shawn P. Conley

Winter wheat acres across WI have declined over the past few years due to late grain harvests, disease concerns (FHB or scab) and poor wheat prices, however anyone that lives and works in WI knows that a base number of cereal acres are needed to support the dairy industry (straw and land to summer haul manure). As farmers get ready to kick off the 2018 growing season here are a few suggestions to help get your 2018/19 winter wheat crop established on time.

  • Plant early. If weather and soil conditions allow for it plant the acreage you intend to go to winter wheat first. This is regardless of which crop you plan to follow (soybean, corn silage or field corn). Remember the optimal planting date window for most of our WI winter wheat acres is the last week of September through the first week in October. In table 1 below you will notice that for every 3 days soybean planting is delayed we see ~1 day delay in beginning maturity (R7), so delaying planting by one week equates to about 2 days later maturing. However when planting is delaying past June 1st it turns in to more of a 1: 1 relationship. Also remember in WI it normally takes another 5-8 days for the soybean crop to move from R7 to R8 (full maturity).

Table 1. Calendar date for reaching R5 (beginning seed fill) and R7 (beginning maturity) growth stage by planting date and maturity group for the 2014, 2015, and 2016 growing seasons at Arlington and Hancock, WI.

Date of Growth Stage Initiation
R5
R7
Planting Date
Maturity Group
Arlington
Hancock
Arlington
Hancock
May 1st
2.5
3-Aug
4-Aug.
14-Sept.
15-Sept.
2.0
30-July
1-Aug.
9-Sept.
14-Sept.
1.5
26-July
29-July
3-Sept.
9-Sept.
May 20th
2.5
7-Aug.
9-Aug.
18-Sept.
20-Sept.
2.0
3-Aug.
7-Aug.
14-Sept.
18-Sept.
1.5
3-Aug.
4-Aug.
6-Sept.
15-Sept.
June 1st
2.0
11-Aug.
12-Aug.
18-Sept.
24-Sept.
1.5
10-Aug.
9-Aug.
16-Sept.
18-Sept.
1.0
7-Aug.
8-Aug.
10-Sept.
14-Sept.
June 10th
2.0
15-Aug.
17-Aug.
25-Sept.
30-Sept.
1.5
14-Aug.
16-Aug.
20-Sept.
25-Sept.
1.0
11-Aug.
14-Aug.
16-Sept.
18-Sept.
June 20th
1.5
21-Aug.
21-Aug.
27-Sept.
2-Oct.
1.0
18-Aug.
18-Aug.
24-Sept.
26-Sept.
0.5
16-Aug.
16-Aug.
19-Sept.
22-Sept.
  • Consider an earlier maturity group soybean. Plant a high yielding, earlier maturity group soybean to help get that soybean crop harvested on time. Though later maturing varieties “on-average” produce the greatest yields, data from our 2017 WI Soybean Variety Test Results show the maturity group range that included a starred variety (starred varieties do not differ from the highest yield variety in that test) was 1.6-2.8, 1.1-2.4, and 0.9-2.0 in our southern, central and north central regions respectively. This suggests that the “relative” maturity group rating is trumped by individual cultivar genetic yield potential. Therefore growers have options to plant an early maturity group soybean that will be harvested on time and not sacrifice yield.
  • Crop rotation matters. Our long-term rotation data suggests winter wheat yields are greatest following soybean, followed by corn silage and lastly corn for grain.  Therefore plan your rotation accordingly to maximize yield and system efficiency.
  • Manage for the system not necessarily the crop. If you are serious about maximizing wheat grain and straw yield on your farm one of the biggest contributing factors for both of these in WI is timely wheat planting. Make management decisions to facilitate that. *We all know what inputs can extend maturity that don’t necessarily guarantee greater yields. So instead of listing them and fielding angry emails I am being strategically vague here*  In a recent study I would note that across years and environments we did quantify a %RYC (percent relative yield change) swing of -4.1% to 11.2% among various soybean inputs so balance that against a loss of 10-20 bushels of wheat grain yield and 0.5 tons of straw?

As we all know mother nature holds the ultimate trump card on whether we will get our winter wheat crop established in that optimal window. These aforementioned strategies are relatively low risk to the farmer and regardless of what weather patterns we run into are agronomically sound.

The WSMB Free Soybean Cyst Nematode Testing Program is Back in 2018!

Ann MacGuidwin, Damon Smith and Shawn P. Conley
The WI Soybean Marketing Board (WSMB) sponsors free nematode testing to help producers stay ahead of the most important nematode pest of soybean, the soybean cyst nematode (SCN). Eggs of SCN persist in the soil between soybean crops so a sample can be submitted any time that is convenient. The soil test report indicates the number of eggs in the sample and is useful for selecting the right variety for the next soybean crop. Retests of fields planted with SCN-resistant varieties over multiple years shows how the nematode population is responding to variety resistance and provides an early warning should the nematode population adapt to host genetics.
In the spring of 2012, the WSMB expanded the nematode testing program to include other pest nematodes in addition to SCN. These nematodes are less damaging to soybean than SCN but can cause enough yield loss to warrant treatment. As is the case for SCN, there are no rescue treatments for nematodes so the primary purpose of this year’s soil test is to plan for next year’s crop. Soil samples collected in corn for nematode analysis have predictive value for explaining yield if they are collected before the corn V6 growth stage. Sampling early in the season will provide information about the risk potential for the current corn crop AND the next soybean crop.
The assays used to recover nematode pests other than SCN in soil require that the nematodes are alive. So, it is important to keep the samples moist and at least room temperature cool. Collecting a sample that includes multiple cores ensures that there will be plenty of root pieces to assay. It is not necessary to include live plants in the sample. The soil test report will indicate which pest nematodes are present and at what quantities and their damage potential to soybean and corn based on the numbers recovered.
For more information on SCN testing and management practices or to request a free soil sample test kits please contact: Jillene Fisch at (freescntest@mailplus.wisc.edu) or at 608-262-1390.
Click to view more information on our WI SCN testing program or visit The SCN Coalition.
Remember the first step in fixing a nematode problem is to know if you have one! The WSMB sponsored nematode testing program provides you that opportunity. So Wisconsin farmers….”What’s you number?”