Volume 7, No. 1, March 2004

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Index


Dear Reader,

Welcome to a new year and volume of the Virginia Soybean Update. In contrast to last year at this time, we have much to be thankful for. We had very good yields last year and at the time of writing, soybean prices are well above $9.00! Nov. 04 futures are above $7.00! The last number is what really excites me. We have a golden opportunity to market next year's and possibly the 2005's crop at profitable levels. I hope you take advantage of it.

I'll be heading to Brazil to attend the World Soybean Research Conference from March 1-5. Afterwards (March 5-8, I'll be touring southern Brazil. During this tour, we'll visit a soybean cooperative, a farm, and Embrapa Soybean (Brazil's soybean research organization). I look forward to the trip and hope to return with information that we can use in Virginia.

This issue will be brief. I'll focus largely on selecting varieties. I've basically just updated last year's issue with additional data. I also briefly discuss the soybean rust situation. I hope to have another newsletter out in late March. Here's to another good year!

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Variety Selection is Critical for Higher Profits

Yields between soybean varieties can vary as much as 15-20% in a given year or location. Many of you have already made their variety selections and I hope information delivered at local County Extension meetings helped. Still, it's difficult to determine whether or not the right choice is being made. Virginia Tech annually conducts 10 replicated soybean variety tests in five regions of Virginia. These regions include the Northern Piedmont (Orange, VA), Southern Piedmont (Blackstone, VA), Northern Coastal Plain (Warsaw, VA), Southern Coastal Plain (Suffolk, VA), and the Eastern Shore (Painter, VA). While it is tempting only to use the results of the test closest to your operation, this is not usually a good idea. It is important that the variety chosen perform well under a number of different environments. Research has shown that highest yielding variety from a single location will always yield less at that same location the following year. In some cases, the highest yielding variety could even yield less than average. On the other hand, the highest yielding variety from multiple-location averages will usually result in high yields at any location in the following year. Therefore it is advisable to look at average yields across locations in addition to selecting varieties based on local yield data.

Multi-year averages give greater confidence to variety performance. The data presented in this newsletter are an average taken from multiple-locations over the past four growing seasons. The list does not include all varieties that have been tested, but varieties with above-average yields that have been tested for at least 2 years in at least 6 locations. The more locations, the more confidence that the variety will perform as indicated. These data are not actual yield in bushels per acre, but an average relative yield compared to other varieties in the test location. Relative yield is calculated by dividing the yield of a variety by the average of all varieties at that location. Relative yields are then averaged across locations. Average relative yields take out some of the bias occurring when averaging over locations when all varieties were not tested at each location.

In addition to selecting varieties based on yield, one should note the herbicide or nematode resistance of the variety. If planting into a historically weedy or nematode-infested field, one should first make their selection based on the ability to control the weeds present and/or on resistance to nematodes. The yield data presented here were obtained from weed- and nematode-free conditions and are not intended to aid in variety selection under conditions of weed or nematode infestation.

Performance details of varieties tested in the Virginia Soybean Variety Evaluation Tests within each location are available at your county Cooperative Extension office or can be found on the web at: www.vaes.vt.edu/tidewater/soybean/variety.html

Before I proceed any further, we should first review steps in selecting the proper variety. I've already mentioned weed control being one of the most important; therefore, I'll not go into detail with Roundup-Ready or STS varieties. I'll first address selecting the proper maturity group

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Choose the proper maturity

Selecting the proper maturity for your area is very important. You should select a maturity group that will mature before frost, but produce adequate canopy to maximize yield potential. Maturity groups (MG) 3, 4, and 5 will meet these criteria when planted full-season. Late MG 5 or MG 6 varieties should be restricted to the southeastern portion or Eastern Shore of Virginia since they will not fully mature before frost in the western and northern parts of the state. Late 5's or early 6's should not be planted in a double-crop system due to a higher probability that the crop will be damaged by frost. Frost does more than defoliate soybeans; as long as there are still green pods on the plant, a frost will lower yield. Only after the R7 stage (physiological maturity), which is indicated by one normal pod on the main stem that has reached its final mature color (not yellow, but brown or tan), has the crop accumulated all its dry matter or seed weight. By this stage, very few leaves should be remaining. Last year, we had an early frost. This frost severely reduced our double-crop yield potential in the northern Piedmont for MG 4's and in the northeast coastal plain with Mg 5's. We also had an early frost in 2000. This has occurred in 2 of the past 4 years. Long-term averages indicate that the probability of an early frost is low. But if experience indicates that frost is occurring in your area before physiological maturity, then use an earlier maturing variety.

Which maturity group for Full-Season Systems?
The following suggestions are based primarily on yield potential, but other factors such as seed quality also influence my choice. In general a late MG 4 or MG 5 is the best choice in Virginia. Exceptions are: late MG 3 or 4 in the northern Piedmont and MG 3 or early 4 for the Shenandoah Valley. Although there have been reports of success using maturity group 3 varieties outside of the northern Piedmont or Shenandoah Valley, I do not recommend them because of the potential for poor seed quality (see Soybean Update, Vol. 5, No. 7). If growing cotton or peanuts, I recommend using only MG 5's. MG 4 varieties will mature in October, usually before or during cotton and peanut harvest. The longer these mature beans remain in the field during warm and humid conditions, the greater the likelihood of poor seed quality. Traditionally, Virginia has been a MG 5 state. However, I would guess that we now grow more MG 4 than MG 5 soybeans. This might be due to the early frost in 2000 and 2003 that hurt our MG 5 varieties. It is also a result of larger acreages and the need to spread out harvest. But, I suspect it is partially due to yield potential. Since Roundup-Ready soybeans took the market, the MG 4 soybeans have, in my opinion, performed better than the MG 5 varieties in several locations (see the tables below). You'll note that the earlier Maturity groups generally did better last year. Last year was a year with very little, if any, moisture stress. While 5 or 10 year average comparisons of maturity groups generally contrast how the weather patterns affects performance, last year's data may give a better indication of actual yield potential. Below are average yields of each maturity group at six locations over the past 5 years in Virginia.

Table 7.1. Average yields of soybean varieties tested in the 1999-2003 Virginia full-season variety tests.
    Maturity Group
Location No. Years 3 E4 L4 5 6
N. Piedmont 5 51.9 51.5 50.8 48.4 ---
S. Piedmont 5 --- 28.2 34.4 39.2 ---
Eastern Shore 5 52.0 52.8 54.7 52.2 48.7
N. Coastal Plain 5 46.0 45.1 44.1 47.7 ---
S. Coastal Plain 5 50.9 52.4 52.5 51.2 51.0
Chesapeake 4 --- 52.2 58.0 55.6 46.2

A few comments should be made about the above locations. The Southern Coastal Plain and Chesapeake soils are classified as somewhat poorly or poorly drained. However, both soils are either artificially drained by ditches and/or tile drainage, making them very productive corn and soybean soils. Some drought stress is common on these soils, but usually not severe. We rarely average less than 50 bushels/acre at either location. When variety tests have been conducted on sandier, well drained soils in Suffolk, then the MG 5 varieties usually out-yielded the MG 4 varieties. The following table is 2003 data; a year of little or no moisture stress.

Table 7.2. Average soybean yields in 2003 Virginia full-season variety tests.
  Maturity Group
Location 3 E4 L4 E5
N. Piedmont 51.6 42.6 47.6 52.7
S. Piedmont --- 34.2 38.7 59.7
Eastern Shore 52.4 62.2 64.2 59.0
N. Coastal Plain 58.7 58.7 58.5 55.5
S. Coastal Plain 56.2 63.5 53.8 53.8

Develop adequate leaf area for double-crop systems

A consideration other than drought avoidance and frost concerns must be taken into account for double-crop systems. This is canopy development. Unless a soybean crop can develop approximately 3.5 to 4.0 complete layers of leaves per area of land, the crop will not achieve its maximum yield potential. These "layers" of leaves can be best represented by an index called leaf area index, or LAI. An LAI of 4.0 is equivalent to a total of 4 sq. feet of leaves per sq. foot of ground (or 4 acres of leaves per acre of ground). Over the past 5 years, we have collected a wealth of information validating the leaf area-yield relationship. In double-crop systems, leaf area commonly limits yield. Therefore strategies to increase and protect leaf area on less productive soils are usually beneficial. A later-maturing variety will produce more leaf area because it is in the vegetative stage for a longer period. Therefore, there is less risk of inadequate leaf area for later-maturing varieties. This concept of adequate leaf area is revealed in average yields of varieties grown in a double-crop system.

Table 7.3. Average soybean yield in the 1999-2003 Virginia double-crop variety tests.
    Maturity Group.
Location No. Years 3 E4 L4 5
N. Piedmont 5 31.5 31.2 31.1 25.7
S. Piedmont 4 --- 27.9 33.3 36.0
Eastern Shore 5 33.0 38.8 37.8 42.3
N. Coastal Plain 5 35.4 40.2 39.2 36.0
S. Coastal Plain 5 35.7 38.0 38.0 42.0
Chesapeake 5 --- 38.3 37.0 36.4

In double-crop soybeans, we are pushing the maturity date back about 1 to 2 weeks because we are planting later. Therefore, we need to tweak recommendations a little. In general, we can back off the full-season recommendations by about 1/2 of a MG. Don't use MG 6 varieties due to frost concerns in any part of Virginia. In the northern Piedmont and Valley, don't use an early or late MG 5 for the same reason. Part of the explanation that some late MG 5 varieties perform well in full-season tests in Virginia and not double-crop test is related to their later relative maturity. In other words, these late MG 5 varieties are likely to suffer yield reductions due to frost in double-crop systems, but not full-season systems. Experience on your farm or in your area should be used to guide your decision in selection of maturity groups for double-crop. The same rule applies: Use the latest MG that will not be affected by fall frost to maximize leaf area and yield potential. I will remind you again that if frost occurs before the R7 development stage (when one pod on the plant has reached its final mature color), yield loss will occur. In most of Virginia, a MG5 will, on average, out-yield a MG 4 when planted double-crop. But this is not always the case. Situations where earlier maturity groups do just as well are on our more productive soils that allow adequate leaf area development. Our Chesapeake location is a good example of this. These soils are wetter and a little higher in organic matter; in general, very good corn and soybean soils due to fewer drought events.

Lack of leaf area was generally not a problem in 2003, therefore this year's data looks quite different than the long-term averages. However, we can still see a trend towards higher yields with later maturity groups in some locations.

Table 7.4. Average soybean yields in the 2003 Virginia double-crop variety test.
  Maturity Group
Location 3 E4 L4 5
N. Piedmont 31.9 33.9 24.5 ---
S. Piedmont --- 38.0 42.7 49.8
Eastern Shore 44.9 47.8 41.6 41.3
N. Coastal Plain 41.6 48.7 44.0 30.0
S. Coastal Plain 43.4 47.3 43.9 50.1

Soil type matters
When will early Maturity groups equal or out-yield later Maturity groups? When the soil or rainfall pattern (basically soil moisture) allows the crop to develop adequate canopy. This was the case in 2003. An early MG (MG 4 in eastern or southern Virginia, MG 3 in northern Piedmont or the Valley) with better genetic yield potential can out-yield a later MG. Therefore soil type is an important consideration when selected double-crop varieties. If the soils yield potential is low, say 20 to 30 bu/A (Rumford, Bojac, Cecil, etc.), then a later maturing variety would better avoid drought and have a longer time to develop adequate leaf area. On the other extreme, a 40-50 bu/A soil with good water holding capacity (Pamunkey, Wickham, State, Davidson, etc.) will likely produce as good of yields from an early as a late variety. For 30-40 bu soils (Emporia, Eunola, Suffolk, etc.), its pretty much a crap shoot depending on how much rain Mother Nature gives us.

Nematode and Herbicide Tolerance
In many cases, soybean varieties should be selected primarily on factors other than yield. Weed and nematode infestations are good ones. The arrival of herbicide-tolerant crops has made weed management much easier and reliable. The presence of weeds can do much more damage to crop yield than poor variety selection (based on yield). Therefore, don't hesitate to use the new technologies if needed.

Determining whether to use an herbicide-tolerant variety is usually easier than determining to use a nematode-tolerant variety. Weeds are much more visible from the windshield. Still, most of us can recognize a nematode infested field near the end of the growing season, although we may not know the problem is nematodes. In many cases, these fields look worse that a weed-infested field and may be just as yield robbing. Therefore, test the soils for nematodes if you suspect a problem. Fall is the best time to do this because nematode populations usually fall dramatically during the winter. Yet, spring is not too late to sample. One thing is for sure. If you have high spring counts, then you definitely need to address the problem.

Of course, the first line of defense is rotation to a non-host crop. If cyst nematode is a problem, then rotation to any crop is effective. However, if root knot is the problem, then it's not as easy. Southern root knot can use corn and cotton as an alternative host, but northern root knot uses only peanut as a host. Regardless, if soybeans must be planted select the appropriate variety. Unfortunately, with the exception of soybean cyst nematode, little is known about the resistance of soybean to other nematodes. The tables on the following pages list those varieties with soybean cyst and root knot nematode resistance.

On the following pages are lists of varieties available in Virginia that have yielded greater than average in the Virginia variety tests over the past 3 years of testing. In addition, I've listed some promising new varieties that I've only tested in limited location in 2003 or other varieties with limited yield data. Note that yields listed are relative yields, not actual yield. Remember, the more observations, the more confident that I am in that variety performing as well next year, regardless of location.

In summary, there are several factors that go into selecting the appropriate soybean variety. I've listed a few of the most important here. In reality, variety selection is very site specific. Knowing weed, nematode, and other pest problems will narrow one's choices rapidly. Choose the proper maturity for your area and field. Then use the tables on the following pages to select a variety that has consistently yielded greater than average over multi sites and years.

More detailed information on Virginia soybean varieties can be found in the following publications:

Characteristics of Soybean Varieties Grown in Virginia. 2004. Tidewater AREC Info. Series No. 457.

Average Relative Yields of Soybean Varieties Tested in the Virginia Official Variety Tests 2001-2003. Tidewater AREC Info. Series No. 456.

Virginia Soybean Variety Evaluation Tests 2003. Tidewater AREC Info. Series No. 454.

All of these publications can be found at the Virginia Soybean Production website: http://www.vaes.vt.edu/tidewater/soybean/variety.html

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Soybean Rust

We must be aware of a potentially destructive disease that is now spread throughout Brazil. This disease is soybean rust. Dr. Erik Stromberg gave an excellent presentation at the Virginia Soybean Conference. There, he described the disease's potential to infest the U.S. and how and where it would most likely enter the U.S. The bad new for us in the Mid-Atlantic states is that we have the weather conditions that would allow the disease to flourish. In addition, wind currents from South America seem to indicate that the first spores (if carried by wind) would land in the eastern U.S. Therefore, let's keep an eye open for this disease this year. If you see any symptoms that look like those shown below, please contact me or your local county extension office. We'll want to send that sample to one of several diagnostic labs in Virginia. More to come on this disease in the future...

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Average Relative Yield Tables

Table 7.5.1. Relative yield of maturity group III soybean varieties grown full-season and tested in at least six locations over the last three years (2001-2003).
      Nematode Resist.    
Brand Variety Herbicide Resistance Cyst Root Knot Average Rel. Yield No. of Rep. Locations
S. States RT-3799N RR R3,14   103 10
S. States SS-381-STS STS     103 7
Other promising varieties tested only in 2003 or in less than 6 locations
Schillinger 393RCP RR *   107 3
Vigoro V38N4RR RR R3   106 3
USG 7393nRR RR *   103 3
HiSoy APK395NRR RR R3   100 3
Garst 3824RR/N RR R3,MR14   100 2
Garst 3712RR/N RR     100 2

Table 7.5.2. Relative yield of maturity group III soybean varieties grown double-crop and tested in at least six locations over the last three years (2001-2003).
      Nematode Resist.    
Brand Variety Herbicide Resistance Cyst Root Knot Average Rel. Yield No. of Rep. Locations
Asgrow AG3701 RR R3   103 7
S. States SS-381-STS STS     103 6
Other promising varieties tested only in 2003 or in less than 6 locations
Garst 3712RR/N RR MR3   114 2
Garst 3824RR/N RR R3,MR14   105 2
Vigoro V38N4RR RR R3   101 4

Table 7.5.3. Relative yield of maturity group IV soybean varieties grown full-season and tested in at least six locations over the last three years (2001-2003).
     Nematode Resist.  
Brand Variety Herbicide Resistance Cyst Root Knot Average Rel. Yield* No. of Rep. Locations
Public Manokin   R1,3 Rai 112 15
DPL SG498RR RR     109 9
DPL DP4748S STS     109 10
DPL DP4690RR RR     107 12
DPL DP3478       107 6
USG 7440nRR RR MR3,14   106 6
USG 7489RR RR     105 9
Vigoro V462NRS RR/STS R3, MR14   105 9
S. States RT-4980 RR     104 12
Delta King DK4868RR RR R5   104 10
Vigoro V442NRR RR MR3,14   103 10
Pioneer 94B73 RR     103 9
NK S46-W8 RR R3,MR14   102 6
S. States RT-4810N RR R3,14   102 8
Asgrow AG4403 RR MR3   102 10
S. States RT-4098 RR     101 12
S. States RT-4502N RR R3,14   101 7
Other promising varieties tested only in 2003 or in less than 6 locations
DPL DP4331RR RR R3   107 4
Seedway SG4775 RR *   105 3
Schillinger 443R RR     104 3
USG 7401nRR RR *   103 3
Stine S4882-4 RR R3,MR14   103 5
DPL DP4724RR RR R3,MR14   103 4
Asgrow AG4502 RR MR3,R9   102 3
Garst D484RR/N RR R3,MR14   102 1

Table 7.5.4. Relative yield of maturity group IV soybean varieties grown double-crop and tested in at least six locations over the last three years (2001-2003).
     Nematode Resist.  
Brand Variety Herbicide Resistance Cyst Root Knot Average Rel. Yield* No. of Rep. Locations
DPL DP4690RR RR     109 10
Pioneer 94B73 RR     109 6
DPL SG498RR RR     108 7
S. States RT-4980 RR     108 12
Vigoro V462NRS RR/STS R3,MR14   106 6
S. States RT-4810N RR R3,MR14   106 7
Vigoro V442NRR RR MR3,14   105 6
S. States RT-4098 RR     103 11
Delta King DK4868RR RR R5   103 9
S. States RT-4502N RR R3,14   101 6
             
Other promising varieties tested only in 2003 or in less than 6 locations
Garst 4312RR/STS/N RR/STS MR3   113 2
S. States RT4230N RR R3,14   106 3
DPL DP4748S STS     106 4
DPL DP4331RR RR R3   106 4
USG 7499nRR RR R3,MR14   105 3
USG 7423nRR RR *   105 3
Garst 4112RR/N RR R3,MR14   104 2
Public K4602   R3   101 10
Pioneer 94M70 RR R3   101 2

Table 7.5.5. Relative yield of maturity group V soybean varieties grown full-season and tested in at least six locations over the last three years (2001-2003).
     Nematode Resist.  
Brand Variety Herbicide Resistance Cyst Root Knot Average Rel. Yield* No. of Rep. Locations
Virginia V96-0340       110 10
USG 5601T     Ri 108 14
Public Delsoy 5500   R3,14   106 11
Asgrow AG5603 RR R3   105 7
NK S56-D7 RR R3,14 MRia 105 6
Public Hutcheson       105 27
DPL DP5110S STS     103 12
S. States SS-5200-STS STS     103 16
USG 570nRR RR R3, MR14   103 6
             
Other promising varieties tested only in 2003 or in less than 6 locations
USG 7524nRR RR R3   112 3
NC N99-186       110 5
Delta King DK5967RR RR MR3,14   109 3
Virginia V98-2711       108 5
USG 5002T       108 3
Pioneer 95B96 RR   MRi 107 4
Asgrow AG5605 RR R3   105 5
USG 7553nRR RR R3   104 3
Dekalb DKB53-51 RR R3   103 5
DPL DP5634RR RR R1,3,MR5   102 4

Table 7.5.6. Relative yield of maturity group V soybean varieties grown double-crop and tested in at least six locations over the last three years (2001-2003).
     Nematode Resist.  
Brand Variety Herbicide Resistance Cyst Root Knot Average Rel. Yield* No. of Rep. Locations
S. States SS-5200-STS STS     109 11
Virginia V96-0340       109 7
Public Anand   R3,5,14   108 11
Public Hutcheson       105 17
DPL DP5110S STS     104 8
NK S57-A4 RR MR3,9,14 Ri,MRj 104 7
Public Accomac   R1,3 Ri 103 11
Virginia 99VPI-120 RR     103 7
Vigoro V503RR RR   Ri 101 7
Public Delsoy 5500   R3,14   101 7
Other promising varieties tested only in 2003 or in less than 6 locations
Virginia V98-2711       120 4
DPL DP5634RR RR R1,R3,MR5   110 3
NK S56-D7 RR R3,14 MRia 107 3
Pioneer 95B96 RR   MRi 106 5
DPL DP5915RR RR R3,MR14   103 5
Hubner H571NRR RR MR3   102 4

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Sincerely,

David L. Holshouser


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