Tag Archives: soybean

Improving Your Soybean Variety Selection Decisions – What maturity is best?

Variety selection continues to be one of the most important decisions that we can make.  It is also one of the first steps to take that insure success.  It’s a hard choice because there are so many varieties available.  Still, this choice is one that will affect your profitability throughout the year.

Soybean yields in our variety tests have increased by an average of 0.4 bushels per year over the last 30 years.  Some of this increase is due to better varieties, some is due to better management.  In those tests, the highest and lowest yielding varieties varied by 20% or more (8-10 bushels).  It is therefore clear that making the wrong choice will seriously impact next year’s soybean crop.  Unfortunately, environment (rainfall, temperature, soil type, field, etc.) affects yield variation more than variety – there is always lots of year-to-year and site-to-site variation.  Still, each variety has specific strengths and weaknesses that make it more or less suited for any given situation.

Putting the Right Variety in the Right Field

With all this variation, it is very important that you place the right variety in the right field.  This will be influenced by 1) planting full-season or double-crop; 2) maturity; 3)herbicide tolerance; 4) disease and/or nematode tolerance; and finally 5) yield potential.  There are also a number of other factors that differentiate varieties such  as shattering and lodging susceptibility, height, branching ability (thin vs. bushy), seed size, seeds/pod, protein and oil content, other specific traits, etc.), but these will rarely affect your bottom line.   Although all of the top five things I listed are important, yield potential is clearly what is of most interest.  However, if you do not pay attention to numbers 1 through 4 first, your yield potential can be low.

To cover all of the things that make variety selection important would take more words than this blog will allow, so we will first focus on the choosing the right maturity.

Relative Maturity Choice: Spreading Out Environmental Risk

First, I should say something about early planting of an early-maturing variety.  I define this as planting in April or early May a variety that is about one full maturity group earlier than the maturity that is most adapted, based on historical data, for your area.  First, early-planted early-maturing varieties will always have a greater risk of poor quality seed.  The seed of these varieties are maturing during September and early October, when the weather is relatively warmer.  Warm and wet weather are perfect conditions for seed decay.  2018 has been one of the worse years for this, primarily due to excessive rainfall and much warmer September temperatures.  To the right is an example of a maturity group (MG) 3 soybean planted in April in Madison County (MG 4 is the most adapted maturity for this area).  Clearly, you don’t want to end up with this.  While early maturing varieties have their advantages, their associated risks should keep the percentage of acres planted to a minimum.

On the other hand, do not keeping all varieties in a tight maturity range.  The performance of varieties within a certain maturity range will almost always depend the environment that they experience during pod and seed fill.  If conditions are good (adequate rainfall, moderate temperatures, good soils) during that time, yields will be high.  Unfortunately, the weather cannot be predicted in our humid southeastern U.S. environment.  While late-July and early-August are generally our hottest and driest times of the year, we have just as good of a chance of going through a hot and dry period in June as well as July as well as August, and sometimes in September.          Still, on average, certain relative maturity ranges yield more than others in the south central part of Virginia.  Below are the average yield balance (no. of bushels/acre greater or less than average) of a range of soybean maturities tested in our full-season variety tests over the last 10 years, separated by location.

I’ll use our Southern Piedmont location (Blackstone) as an example of a location that shows the greatest yield gap between the earliest and latest varieties (nearly 15 bushels!).  This is likely due that area typically experiencing the more stress (hot and dry) from late July through August than other regions.

Similar but on the opposite end of the spectrum, MG 3 and 4 varieties work best at the Northern Piedmont (Orange) location.  Maturity group 5 varieties generally not as adapted in that northerly environment.

The northern and southern Coastal Plain sites (Warsaw and Suffolk) behave similarly to Blackstone – MG 5 outperform MG 4 varieties; but the yield gap between relative maturities is not as wide.

Our Eastern Shore location does not follow the same trend of MG 5’s being the highest average yielding varieties as one moves south and east.

Note that maturity group (MG) 5 varieties relatively better in the more eastern and southern locations of Virginia’s mainland, while MG 4 varieties tend to do better in our most northwestern location (Orange) and on the Eastern Shore (Painter).  While MG 3’s don’t yield as well, the group 4’s are the highest yielding.  Why?  I attribute it to two things: yield potential and temperature.  In general, this site has over time been one of our highest yielding sites.  Although rainfall patterns are similar to other locations in Virginia, it is our coolest location (and there is usually a breeze) – both likely a water effect.  Therefore, the site experiences less stress.  So, pushing the critical pod- and seed-filling stages slightly earlier in the year are not as problematic.

So, should you stick only with maturities that perform best on average?  Not necessarily.  Using Blackstone as an example, note that although the late-group 4 varieties yield less than MG 5’s on average, they yield much better than earlier 4’s.  And late-4’s yield just as well as 5’s in Orange and Suffolk.  I stress that these are averages – 10-year averages of all varieties within those relative maturity ranges.  Is it possible for the MG 4 varieties to yield more than the 5’s in Blackstone or Warsaw?  Is it possible for MG 5’s to yield more in Painter?  Yes!  It just does not happen as often.

We took that same data and calculated the probabilities, not absolute yields, of obtaining similar or greater yields of all relative maturity groupings tested.  The results are below.

Once again, to use the Blackstone data as an example, we can see that growing a late-MG 5 variety will yield at least as much as all of the other relative maturities 90% of the time (bar height).  In addition, there is a 50 to 60% chance (height of the hatched portion of the bar) that the 5’s will yield significantly more than the 4’s.  So, it seems that you will never go wrong with those varieties, correct?  You’ll probably (~80% chance) not go wrong by growing a large percentage of those varieties, but should you should you only plant MG 5’s?  I suggest that you do not grow only MG 5 varieties.  There is still a 10 to 20% chance that the 5’s will yield less than the other maturities.  Plus, there is a 60% chance that late MG 4 varieties will yield just as much as MG 5 varieties (and a 30% chance that they will yield more).

Painter is another good example.  Although there is a yield gap between the 4’s and 5’s, there is a 50 to 70% chance that MG 5 will yield as well as MG 4 varieties.  And there is a 30% chance that they will yield more!  You can use the same thought process for the other locations.

Below are the same graphs for double-crop tests.The Right Mix of Maturity Groups in Virginia.  So, what is the right mix of maturity groups?  I suggest the following:

Southern Piedmont

  • Plant 60 to 80% of your land to MG 5 varieties. We have also found that later maturities generally do better on our more droughty soils, so take that into consideration if possible.
  • Plant 20 to 30 % to late-MG 4 varieties (4.7-4.9). If possible, plant these on your higher-yielding soils.  We have found that this range of maturities have our greatest yield potential throughout Virginia if the weather cooperates.
  • Plant 0 to 20 % to mid-MG 4 varieties. These are risky, especially on droughty soils or in double-crop settings.  It is highly likely that these varieties will experience some (or a lot) of stress during the seed and pod fill stages.  Plus, seed quality will almost always be poorer than other maturities.  If you do grow these, harvest as soon as possible as seed quality will continue to degrade with time.  Don’t plant these in April or early May. This places the most critical times of development (pod and seed fill) during late-July and August.  And seed quality will be even worse since they will likely mature during the warmer part of the year.  Still, yield potential can occasionally be quite high.

Southern Coastal Plain (same comments apply regarding droughty soils and seed quality)

  • Plant 30 to 60% of your land to MG 5 varieties.
  • Plant 30 to 50 % to late-MG 4 varieties (4.7-4.9).
  • Plant 10 to 20 % to early- and mid-MG 4 varieties.

Northern Coastal Plain (same comments apply regarding droughty soils and seed quality)

  • Plant 30 to 60% of your land to MG 5 varieties. In double-crop systems, reduce that percentage to 30 to 50%.
  • Plant 30 to 50 % to MG 4 varieties (4.7-4.9). In double-crop systems, increase that to 50 to 70% late-4’s and plant 10-20% early-or mid-4’s.
  • Plant 0 to 20 % to late-MG 3 varieties.

Eastern Shore (same comments apply regarding droughty soils and seed quality)

  • Plant 20 to 40% of your land to MG 5 varieties.
  • Plant 50 to 70 % to late-MG 4 varieties (4.7-4.9).
  • Plant 10 to 20 % to early- and mid-MG 4 varieties. Plant 0-10% in double-crop.
  • Plant 10 to 20% to late-MG 3 varieties.

Northern Piedmont (same comments apply regarding droughty soils and seed quality)

  • Plant 0 to 20% of your land to MG 5 varieties. Don’t plant MG 5’s double-crop.
  • Plant 60 to 80 % to MG 4 varieties (4.7-4.9).
  • Plant 10 to 20 % to mid- or late-MG 3 varieties.

The proportion of MG 4 and 5 will ultimately depend on your risk tolerance.  Note that as you move west and north, the risk of an early frost is greater; therefore, growing lots of late-maturing varieties may not be a great idea, especially double-crop, and the probability of slightly earlier maturities doing better is greater.

Hopefully, this will give you some guidance in choosing your maturities within the next few weeks.

IMPORTANT:  Keep in mind that the yields and yield balances shown are an average of all varieties in those relative maturity groupings.  This does not mean that every variety in those grouping perform in this manner on every field.  Make sure that you first the variety that meets your match your field’s pest management needs; then, select a high-yielding variety within that relative maturity range.

 

Virginia Soybean Yield Contest

The purpose of the Virginia Soybean Yield Contest is to emphasize and demonstrate the practices necessary to produce maximum economic yields, to recognize those producers who grow high-yielding soybeans, and to gather data on the practices utilized by these outstanding producers.
The Virginia Soybean Association in cooperation with Virginia Cooperative Extension sponsors this program.
There are four Soybean Yield Contest categories: 1) Full-Season, Non- irrigated; 2) Double-Crop, Non-irrigated; and 3) Irrigated (Full-Season or Double-Crop; and 4) Most Efficient. A full-season system is defined as the grain or seed harvest of one summer crop (soybean in this case) from the same field in one year. Double-crop is defined as planting soybean immediately following grain harvest of barley or wheat; thus harvesting two crops from the same field in the same year. If soybeans are planted after a cover, silage, or hay crop of small grain, then the entry will be considered full- season. If field has been irrigated one or more times, the entry will be considered an irrigated field and the will be placed into the irrigated contest. Yield alone (bushels/acre) determines the winners in the first three categories.
Notice of intent to participate must be submitted to your county/city Extension Agent’s office 5 days before harvest or in an acceptable time frame for your Extension Agent. Extension Agents shall maintain the original set of record sheets and applications of all participants and send a copy to Dr. David L. Holshouser, Extension Agronomist, Tidewater Agricultural Research and Extension Center, 6321 Holland Rd, Suffolk, VA 23437 by Dec. 31.
Application forms and a complete set of rules and regulations can be found on the Soybean Yield Contest website.

Soybean Sprouting in the Pods/Pod Splitting

We are seeing immature soybean once again sprouting in the pods in Suffolk and Gloucester County, and I heard of this happening in other states.  This seems to occur every 3-6 years somewhere.  Although I don’t have a great explanation for why this occurs, it usually happens when there are good growing conditions early followed by 2-4 weeks of drought stress during pod formation, and then excellent conditions return for seed fill.  Typically, it happens in big-canopied soybean (lots of leaf area) with lots of yield potential, but not enough pods (or big enough pods) to fulfill that potential.  I think that the seeds enlarge so much that the pod splits.

Keep in mind that I’m talking about immature seeds and pods.  This can also occur after the crop matures (R7 to R8) when we get excessive rainfall after the seed in question has dried down.  But, I have not seen that yet this year.

There is little that you can do about it.  Those sprouted seed will usually dry up on the plant and be blown out the back of the combine.

Although there has to be some yield loss, I’ve not seen it to be very great.  And, I suspect that if you did not notice the sprouted seed, you probably would not know that you had a loss.

For more information, see previous blogs on this subject.

Wet Conditions May Lead to Soybean Seed Sprouting

The Good and Bad of a Wet September

Finishing Out the Soybean Crop – What do we need for Good Yields?

In general, we’ve had a good, but not great year for soybean in Virginia.  Although many areas were hit with a 3 to 4 week dry spell during July, August rains kept us in the game.  However, we did not see the ample  rains or cool temperatures that we experienced in August of 2017, which resulting in record yields.  Below is a summary of August rainfall and temperature anomalies for the U.S.

 

 

 

 

 

 

 

 

As you’ll notice,  we had about average or slightly below average precipitation and average to slightly above average temperatures for most of Virginia’s soybean growing areas.

So, I do not suspect that our yields will be as good as last year.  Still, our earlier-maturing varieties planted in April or May should yield quite respectably considering that most have made over 50% of their yield – they have reached the R6 stage (see photo below).  Yield of our later-maturing varieties, planted in May and early June, and our double-crop plantings are not quite there yet – much of our yield is yet to be determined – R5 soybean have only made roughly 25% of their yield at that time.

So, what do we need for good yields?  Rain is obvious.  Full-canopied plants with adequate soil moisture will draw about 0.25 inches of water/day from the soil.  But, we also need cool temperatures – soybean do not generally like 90+ degree days, especially when forming seed.

Below is the 10 day rainfall and temperature forecast for the U.S., and it does not necessarily look good for us.  Note that the rainfall is predicted accumulation and the temperature map shows anomaly.  Although we should get some rain this weekend only (more in northern parts), temperatures are supposed to be above average.  But, forecasts are only forecasts.  The weather does change.  I hope we will get the needed rainfall that they are predicting this weekend.  But a big ridge appears to be setting up over the Mid-Atlantic states for next week.  This usually means warm weather and only at the edges of ridges do we normally see rainfall – note the heavy rainfall predicted from Nebraska through Michigan.

 

 

 

 

 

 

I don’t mean to discourage, just to inform.  We still have decent soil moisture, at least in the subsoil.  With rain this weekend, we should get through next week without too much harm to the crop.

Our double-crop soybean (assuming late maturity group 4’s and group 5’s planted in late June to July) are just now in the R5 stage – it usually takes 80 to 100 days from planting to reach R6, depending on maturity and planting date.  So some timely September rains will usually result in good double-crop soybean.

When will our yield be “made”?  Below is table showing the number of days to soybean physiological maturity (R7; 95% of yield has made).  When can we expect to be harvesting our soybean?  Full maturity is reached about 2 weeks after R7 and harvest can proceed after the soybean have dried down to a harvestable moisture, usually within a week after R8.

Walk Your Fields

For greater soybean yields, one of the best things that you can do is walk your fields.  Many problems reveal themselves during the summer.  Actions taken or not taken can be very noticeable.  By walking fields, we can see what’s working and what’s not working.  Certain problems can be solved, some cannot.  For those that cannot be solved this year, we can do better next season by understanding why we have the problem.  Therefore, a review of how to diagnose your crop will likely beneficial.

A few years ago, I published “Troubleshooting The Soybean Crop“.  Although a little dated, most of the information is still good.  This publication will guide you through how to go about diagnosing problems, includes a vegetative- and reproductive-stage outline with lots of photos, and also includes a sample crop scouting and diagnostic form.  You can download a view a PDF copy, or contact me – I still have a few hard copies left.  By following some general guidelines, one can become quite good at diagnosing problems.  Below is a summary.

First, document everything!  Memories tend to fade.  We often forget or overlook details. You can document by taken notes (many phone apps or iPad/tablets work well for this).  Make a recording.  Take pictures – this is especially useful when you need help – and send those photos to others.

PRELIMINARY FACT FINDING.  You can obtain plenty of information before you even get to the field.  Although I call this preliminary (as if you’ve not seen the problem), you may need to go back to the office to refresh your memory of what you did.  Information that can be acquired beforehand or back in the office includes:     

  • Cropping History
  • Equipment
  • Soil Information
  • Weather
  • Pest Management Information
  • Tillage and Other Cultural Practices

THE FIELD VISIT

  • Take all materials and equipment needed (e.g., phones, paper, shovel, plastic bags, soil probes, etc.)
  • Windshield/Whole Field Investigation
  • Above-Ground Inspection
  • Take Appropriate Plant or Soil Samples
  • Equipment Check
  • Interaction with Others
  • Document Everything!

ANALYSIS OF DATA AND FINDINGS

  • Patterns
  • Look-Alike Symptoms
  • Interacting Factors/More Than One Problem

DRAWING A CONCLUSION. Review the facts and data.  Eliminate unlikely causes.  Validate likely causes.  You may be able to drawn a conclusion in the field, but lab analysis may be needed.

FOLLOW UP. Revisit the field.  If you took corrective action, did it work?  Why or why not?

This is a very rough outline of the guide.  Again, if you want a hard copy of Troubleshooting The Soybean Crop, contact me.

Yellow soybean leaves may be due to manganese (Mn) deficiency

Manganese (Mn) deficiencies are common in Virginia soybean and are starting to appear in numerous fields.  These deficiencies are not necessarily due to low Mn levels in the soil, but are more likely related to high soil pH levels, as its availability decreases with increasing soil pH.

Although soils with a pH of 6.2 or lower can occasional show Mn deficiencies, it is most likely to appear when pH levels reach 6.5 or above.  Furthermore, Mn deficiencies are more common on our sandier soils because pH changes more rapidly and these soils typically have a lower concentration of the nutrient.

The deficiency will appear as interveinal chlorosis, usually on the younger leaves first since Mn is not a mobile nutrient.  MnDeficiency0721101059This may distinguish Mn deficiency from magnesium (Mg) deficiency.  Magnesium deficiency symptoms will usually appear on the lower leaves while the upper leaves remain green.  Still, I’ve seen Mn deficiency on the lower to middle leaves.  This usually happens when the field has not been checked in a while and the observer missed the symptoms when they were on the younger leaves.Cyst nematode on roots

Other problems can cause look-alike symptoms similar to Mn deficiencies.  In particular, interveinal yellowing is a common symptom of soybean cyst or other nematode damage.  Therefore, it may be prudent to further investigate the problem, especially the root system.

Use the following guidelines for Mn applications:

Scout your fields.  Mn deficiencies may or may not materialize.  The only sure way to determine a deficiency is to observe the deficiency symptoms through visual observation or tissue tests.  The characteristic visual symptom is yellowing between the veins on the new leaves.  Mn is an immobile nutrient.  Therefore, it will not move out of older leaves to the new leaves.  Symptoms will appear when the plant can no longer extract sufficient amounts of the nutrient from the soil.

Take a tissue sample.  If Mn deficiencies are suspected due to high pH and/or a field history of Mn deficiencies, but no symptoms have yet appeared, you should consider taking a tissue sample.  Tissue samples can reveal deficiencies before symptoms appear (hidden hunger).  We suggest a tissue test if lime, lime stabilized biosolids, or an ash product was recently applied.

Manganese application.  To overcome a deficiency, apply ¾ lb. chelated Mn (elemental basis) or 1 lb. inorganic Mn (elemental basis) per acre to foliage upon appearance of symptoms and prior to flowering.  More than one application may be required to correct a severe deficiency.

Don’t use low rates to correct a deficiency.  Note that many Mn products recommend applying lower rates of Mn.  However, the label usually states that these are maintenance rates.  Once a deficiency occurs, these lower rates will not correct the deficiency and the rates stated above will be needed.

Split Mn application on deficiency-prone soils.  An alternate method of application can be used before a deficiency is evident on soils that commonly show a deficiency, especially on soils that have a high pH (above 6.8 or so).  A lower rate (~ ½ of that listed above) can be combined with another scheduled application, such as a postemergence herbicide or insecticide.  This may be a sufficient rate to prevent a deficiency from occurring.  But, continue to scout the field and take future corrective measures if visual deficiencies appear.  If a visual symptom appears, you need to use the full rate.  I will remind you that this is a preventative treatment.  A deficiency may not occur.  Furthermore, these are only maintenance rates and another application will likely be needed if the field is truly deficient.

Use EDTA chelated Mn formulations when mixing with glyphosate.  Be reminded that some Mn formulations in combination with glyphosate herbicide (Roundup, Touchdown, many generics, etc.) will result in reduced weed control of certain weeds.  Other herbicides have not shown to interact.  If including Mn with glyphosate, use the EDTA chelated formulation as it has shown not to interact.

Don’t spray if you don’t need it.  In addition to the cost, Mn can be toxic to soybean.  Spraying greater than recommended rates or spraying as a preventative spray when soil pH is relatively low (5.7-5.9) could lead to toxicity problems

Wet Soils, Poor Stands – Do I Replant?

The decision of whether or not to replant arises every year; however, the wet soil conditions seem to have worsened the problem this year.  There of course will be areas that the decision is easy – flooded areas resulting in almost no stand.  But, what about fields that just are not living up to your expectations?  I’ve seen and heard many reports of stands being reduced 25 to 50% of what was expected (keep in mind that our expectations are sometimes too high).

First, I must mention that final average stands of 60,000 to 80,000 plants/acre rarely profit from replanting.  Only when you get below 50,000 can it be economically justified.  I refer you to the seeding rate data shown.  Note that yield does not fall off until seeding rates fall below 90 to 120 thousand seed/acre (76 to 107 seed/acre on productive soils).  Stands generally averaged 75%; so, this is equal to  65 to 90 thousand plants/acre.  Once you add in the cost and of and time required to replant, it’s not usually worth it – unless the stand less than this.

 

 

Steps to Estimate the Profitability of Replanting Soybean

Determining whether or not to replant is hard.  To ease the pain, I’ve summarized some relatively simple steps to help in your decision.  One should incorporate 2- to 3-foot gaps into your decision to improve the estimation of yield loss.

  1. Determine the cause of the poor stand.  Was the poor stand the result of poor seed quality, cold wet soils, hot dry soils, planting too deep or shallow, soil crusting, herbicide injury, insect or slug feeding, poor soil to seed contact, or disease infection?  Determine if the cause can be corrected to avoid a similar situation.  If slug or insect feeding or disease is the cause, then you might expect poor stands again.
  2. Estimate the stand and percent stand loss due to gaps.  Pace off the sections of row 20 paces long in at least 6 areas of the field.  Determine (in number of paces) the total length of row lost to 2- to 3-foot gaps.  For drilled soybean, this can be interpreted at 2- to 3-foot diameter gaps.  Then determine the percent of row lost to gaps.  In addition, count and determine average number of plants per foot in sections of row not reduced by gaps.  The simplest method is to count the number of healthy plants (capable of recovery) in a length of row equaling 1/1000 of an acre.  For instance:
  • 36-inch rows = 14.5 feet
  • 30-inch rows = 17.5 feet
  • 20-inch rows = 26 feet
  • 15-inch rows = 35 feet
  • 7.5-inch rows = 70 feet

Then, just multiply your counts by 1,000 to get plants per acre.

Or, use the Tables 1 or 2 to determine remaining plant population.  The “hula hoop” method (Table 2) is valuable with drilled soybean or when rows cannot be distinguished.  This involves placing a circular measuring device such as a hula-hoop on the ground and counting the plants contained within.

Table 1. Plant populations of different row spacing with different plant counts per foot.
Plants/ foot Row Spacing
36 30 24 20 15 7.5
Plant Population (1,000’s/acre)
1 15 17 22 26 35 70
2 29 35 44 52 70 140
3 44 52 65 78 105 210
4 58 70 87 105 139 278
5 73 87 109 131 174
6 87 105 131 157 209
7 102 122 152 183 244
Table 2. Hula-hoop method for determining drilled soybean populations.
No. ofPlants Inside Diameter of Hula Hoop
30” 32” 34” 36” 38”
Plant Population (1,000’s/acre)a
6 53 47 41 37 33
10 89 78 69 62 55
14 124 109 97 86 77
18 160 140 124 111 100
22 196 172 152 136 122
26 231 203 179 160 144
aPlants/acre = no. plants ¸ (3.14 x r2 ¸ 43,560 ft2) where r = radius of hula hoop in feet.
  1. Estimate the yield of the poor stand.  Use Tables 3 and 4 to determine percent of yield potential for full-season and double-crop plantings, respectively.  Note that Table 3 is data from Illinois from the 1980’s. In my opinion, the remaining plant population numbers are too high.  Although I have not conducted full-season plant population studies that have included gaps, I suggest that you change those numbers to  60, 90, and 120 (based on Virginia data).  Multiply this percentage by the expected yield. This is the yield to expect from the deficient stand.
    Table 3. Yield response (% of maximum) of full-season soybeans to deficit standsa.
    % Stand lost to gapsb Remaining Plant Pop (1,000’s/A)
    70 105 140
    0 95 97 100
    10 93 96 98
    20 91 93 96
    30 88 90 93
    40 83 86 89
    50 78 81 84
    60 73 75 78
    aSource: Pepper and Wilmot.  Managing Deficit Stands. 1991. Illinois Cooperative Extension Cir. 1317.bGaps of 12 inches or more; 30-inch rows

    Note that these data are from Virginia.

    Table 13.4.  Yield response (% of maximum) of double-crop soybeans to deficit standsa.
    % Standlost to gapsb Remaining Plant Pop (1,000’s/A)
    100 140 180 220
    0 80 88 95 100
    20 71 79 86 91
    40 61 69 76 81
    60 48 57 64 69
    aSource: 2001-2004 experiments, Suffolk, VA.bGaps of 3 feet; 15-inch rows; MG 4 variety
  2. Estimate the yield from replanting.  After mid-June, decrease the expected yields an additional half of a bushel per acre per day delay in planting.  This is the yield to expect from delayed planting.
  3. Determine the gain or loss from replanting.  Subtract the expected yield of the poor stand (step 3) from the yield expected from delayed planting.  This is the gain or loss in bu/A from replanting.  Multiply this number by the expected price ($/bu), using future prices, to obtain gain or loss in $/A.
  4. Estimate the cost of replanting.  Include per acre cost of tillage, herbicide, fuel, seed, and labor.
  5. Determine profitability of replanting.  Subtract your cost of replanting from your estimated gain from replanting.

 

 

Flooded Soybeans – How Much Damage? What to do?

Rainfall across the state resulted in in saturated soils and sometimes flooded soybeans or fields to be planted in soybean.  Although fields are drying out, more rain is expected this weekend.

It’s difficult to know the long-term effect of flooding on soybean fields. Research is limited, but we do know that the fate of flooded fields will largely depend on 1) the development stage during which the flood took place; 2) the duration of the flood; 3) the temperature during and right after the flood; and 4) the drying rate after the flood.

Basically a flooded field depletes the roots of oxygen (O2), causing photosynthesis to slow.  After several days without O2, the plant may turn yellow, grown very slowly, and possibly die.  Other indirect effects of flooding can include reduced nitrogen-fixing bacteria (but they will recover), nutrient imbalances, and increased disease pressure.

For more detailed information, see a blog post that I wrote  in 2013 at the Virginia Soybean Update site.

In short, here are a few pointers for flooded fields.  If soybean have not yet been planted:

  1.   I don’t recommend tillage to dry the soil out for continuous no-till fields.  Tillage will destroy the soil structure that you’ve built since tillage was stopped.  The field is probably draining better than it ever was; tillage will just cause water to stand longer in the future.
  2. Bradyrhizobia japonicum, the nitrogen-fixing bacteria that helps provide soybean with that nutrient, is harmed by lack of oxygen caused by the flood.  Although the bacteria will recover, it may be prudent to add inoculant to the seed in areas that were flooded.

For flooded fields that have been planted:

    1.  Minimize any addition stress by staying out of the field.  Do not try to plant or replant too soon.  More damage can be done to the soil and more yield can be lost from planting into we soils than from planting too late.
    2. If soybean have not yet emerged and crusting evident, light tillage with a rotary hoe will help emergence.
    3. Evaluate the stand. If a stand reduction occurred, determine if it’s worthwhile to replant. Remember that after mid-June, every day delay in planting will cost you about ½ of a bushel in yield. The plants that remain are still higher yielding than seed that can now be planted, even if the stand has been substantially reduced.
    4. Stress such as herbicide injury can slow the crop down further. Still, weeds need controlling. But you may want to select herbicides (usually as tank-mix partners to glyphosate) that don’t cause a significant amount of burning.
    5. Finally, some will want to apply some type of foliar fertilizer to the crop to “kick-start” it back to health.  I see little advantage of this.  Remember that the real problem is lack of O2 to the roots and CO2 buildup in the soil; only after the roots begin to receive O2 will the recovery process start.Hopefully you haven’t experienced severe flooding (> 24 hours).  But if so, be patient and evaluate the field.  Then make good decisions on how to handle it.