Volume 9, No. 1, March 2006

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Index


Dear Reader,

Welcome to a new year and volume of the Virginia Soybean Update. In this issue, I've addressed one of your most important decisions, variety selection. I hope everyone was or is still able to obtain some good varieties. Word on the street is that see may be in short supply. Yes, we have certain varieties in short supply every year, but due to the seed quality issues last year in the Mid-Atlantic and Delta states, supply of seed is a bigger issue. I hope you find this information useful in your last minute variety selection.

Soybean rust seems to be over-wintering farther north than last year in the Southeast. The warm winter hasn't allowed complete kill of kudzu in protected areas (in culverts, on S side of buildings, etc.). It was just confirmed that it also overwintered in south Texas. So, rust may have somewhat of a head start this year. I'll update you on soybean rust in the next newsletter. For the latest information, access the USDA soybean rust web page: http://www.sbrusa.net/.

If you know of anyone who would like to receive this newsletter, please let me know. I can put them on my mailing list. On the last page is an application form. You don't need to fill this out if you're already a subscriber. Be aware that all past issues are available on the Virginia Soybean website.

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High Yields Begin with Variety Selection

Many have already made their variety selections. That's good because the word is that maturity group 5 varieties will be in short supply due to the seed quality problems last spring. Maturity group 4's seemed to fair better, but one should not wait too late to place your order or the best varieties may be gone.

Virginia Tech annually conducts 10 to 12 replicated soybean variety tests in six regions of Virginia. These regions include the Shenandoah Valley, Northern Piedmont (Orange), Southern Piedmont (Blackstone), Northern Coastal Plain (Warsaw), Southern Coastal Plain (Suffolk/Chesapeake/VA Beach), and Eastern Shore (Painter). Last year's variety test results can be found at: www.vaes.vt.edu/tidewater/soybean/variety.html

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 almost always result in high yields at any location in the following year. Therefore it is advisable to look at average yields across locations and years in addition to selecting varieties based on local yield data.

Multi-year averages give greater confidence to variety performance. The data presented on the following pages are an average taken from multiple-locations over the past three 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 higher the number of observations, 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 and all varieties were not tested at each location.

In addition to selecting varieties based on yield, one should note the disease and nematode resistance of the variety. The incidence of nematodes and frogeye leaf spot is increasing in Virginia fields, so you may want to first select varieties with resistance, especially if you've had problems in the past. You need to especially pay attention to these resistance traits if you're not rotating. Keep in mind that the yield data presented here were obtained from relatively pest-free conditions and are not intended to aid in variety selection under conditions of disease or nematode infestation.

Before I proceed any further, we should first review steps in selecting the proper variety. I'll first address selecting the proper maturity group

Choose the proper maturity

Maturity is of utmost importance. In general, one 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 in Virginia 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. As occurred during the falls of 2000 and 2003, frost reduced yield of MG 5 varieties planted double-crop. If experience indicates that frost is occurring before R7, then use an earlier maturing variety.

Will MG 3 Varieties Work in Virginia?

Last season was an unusual one for Virginia. In an unusual turn of events, MG 3 varieties, when planted in May, yielded as well and sometimes better than MG 4's and 5's (table 9.1.1; Orange was an exception). Most of you will realize that the August and September drought was the cause of this. But, in Virginia, we are as likely to get drought conditions in June or July as August. Plus, we tend to get rain from tropical systems in late August and September. The take home message: Don't expect MG 3 varieties to perform as well, relative to MG 4's or 5's, as they did last year. Keep in mind that I'm talking about the coastal plain and southern Piedmont areas. MG 3's fit well in the Northern Piedmont and Shenandoah Valley.

Table 9.1.1. Average yields of soybean varieties tested in the 2005 Virginia full-season variety tests.
  Maturity Group
Location 3 E4 L4 5
Blackstone --- 34.4 39.0 33.9
Orange 26.3 32.2 38.4 45.8
Painter 56.7 59.1 59.3 54.4
Shenandoah Valley 36.3 38.7 34.0 ---
Suffolk 59.1 57.5 49.7 43.3
Warsaw 42.9 39.7 29.7 38.5

Does this mean that an early maturity variety should not be included in your plans for 2006? No, not at all! From the standpoint of spreading risk and spreading out the harvest season, they may have a fit. Many growers have substantially increased their soybean acreage. Integrating earlier maturity groups would help spread the work load. But, I wouldn't plant the entire farms to them. Nor would I put more than 10 to 20% into early varieties. Keep in mind that seed quality deteriorates rapidly when the crop matures in September due to warm conditions. Harvest cannot be delayed.

One of my requirements for selecting a variety is to insure adequate canopy development. Can a MG 3 accomplish this in a full-season system? Our research indicated that yes, it would usually accomplish this. But, that's not the real yield limitation. You may hear a lot about the success of the Early Soybean Production Systems, or ESPS, in the mid-South. In this system, they plant an early-maturing variety in April (sometimes late-March). This allows them to avoid August heat and drought (August droughts are very common in the Mid-South) and harvest early. But, will such a system work in Virginia? Our research indicates that soybean yields with this system (planting a MG 3 variety in April and maturing the crop in early September) are rarely competitive with planting a later MG in May. We related this to the MG 3 variety experiencing more drought stress in July, when that MG is producing pods and filling seed. In addition, we've found that seed quality rapidly deteriorates in September. This is not to say that such a system does not have a niche fit in some of Virginia - it does. But, it should not be used a method to consistently increase yields. I've not investigated these systems under irrigation.

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 planting large acreages of MG 3's because of the potential for poor seed quality. On the Eastern Shore, all maturity groups have performed well. If growing cotton, I recommend using only MG 5's. MG 4 varieties will mature in October, usually before or during cotton harvest. The longer these mature beans remain in the field during warm and humid conditions, the greater the likelihood of poor seed quality. On the following page are average yields of each maturity group at six locations over the past 5 years in Virginia.

Table 9.1.2. Average yields of soybean varieties tested in the 2001-2005 Virginia full-season variety tests.
  Maturity Group
Location Years Tested 3 E4 L4 5
N. Piedmont 5 46.7 44.5 47.6 45.1
S. Piedmont 5 --- 35.7 41.0 41.7
Eastern Shore 5 52.8 53.2 53.7 50.7
N. Coastal Plain 5 46.5 45.9 44.4 48.3
S. Coastal Plain 5 52.7 55.4 54.5 53.0

A few comments should be made about the above locations. The Southern Coastal Plain soil is classified as poorly drained. However, tile drainage has been installed in that soil, making it very productive. Some drought stress is common on that soil, but it is usually not severe. I've never averaged less than 50 bushels per acre in that location. When variety tests were conducted on sandier, well drained soils in Suffolk, then the MG 5 varieties usually out-yielded the MG 4 varieties.

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 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.

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 _ 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.

Table 9.1.3. Average yields of soybean varieties tested in the 2001-2005 Virginia double-crop variety tests.
  Maturity Group
Location Years Tested 3 E4 L4 5
N. Piedmont 5 28.7 25.1 29.8 ---
S. Piedmont 5 --- 36.9 41.2 40.5
Eastern Shore 5 34.1 37.6 37.2 41.4
N. Coastal Plain 5 33.4 37.9 37.7 33.1
S. Coastal Plain 5 37.0 41.7 41.4 44.9

Soil type matters

When will early MG's equal or out-yield later MG's? When the soil or rainfall pattern (basically soil moisture) allows the crop to develop adequate canopy. In this case, an early MG 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.

In summary, there are several factors that go into selecting the appropriate soybean variety. I've listed a few of the most important here. And don't forget disease or nematode resistance. In reality, variety selection is very site specific. Knowing disease, 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.

Table 9.1.4. Average relative yield of maturity group III soybean varieties grown full-season and tested in at least 6 locations over the last three years (2003-2005).
    Herbicide Resistance Nematode Resist. Frogeye Leaf Spot Resist. Avg. Relative Yield (No. Locations)
Brand Variety Cyst Root Knot
Vigoro V38N4RR RR R3     105 (6)
Vigoro V39N4RR RR R3, MR14     104 (8)
USG 7393nRR RR R3, MR14     102 (6)
Garst 3824RR/N RR R3,MR14     100 (6)
Other promising new varieties (tested in less than 6 locations)
Progeny 3900 RR       104 (5)
S. States RT-3851N RR R3,14     104 (5)
S. States RT3951N RR R3,14     104 (5)

Table 9.1.5. Average relative yield of maturity group III soybean varieties grown double-crop and tested in at least 6 locations over the last three years (2003-2005).
    Herbicide Resistance Nematode Resist. Frogeye Leaf Spot Resist. Avg. Relative Yield (No. Locations)
Brand Variety Cyst Root Knot
Vigoro V38N4RR RR R3     104 (6)
S. States RT3802N RR R3,14     93 (8)
             
Other promising new varieties (tested in less than 6 locations)
Dyna-Gro DG33A37 RR R3, MR14     113 (4)
S. States RT3851N RR R3,14     107 (4)

Table 9.1.6. Average relative yield of maturity group IV soybean varieties grown full-season and tested in at least 6 locations over the last three years (2003-2005).
    Herbicide Resistance Nematode Resist. Frogeye Leaf Spot Resist. Avg. Relative Yield (No. Locations)
Brand Variety Cyst Root Knot
USG 7434nRR RR R3     115 (7)
USG 7440nRR RR MR3,14   MR 108 (10)
USG 7443nRR RR MR3,14   R 107 (8)
Vigoro V442NRR RR MR3,14     107 (10)
D&PL DP4748S STS       106 (9)
DeKalb DKB46-51 RR R3,14   MR 106 (6)
Asgrow AG4903 RR/STS     MR 106 (7)
Delta King DK4868RR RR R5, MR2,6     104 (11)
Asgrow AG4502 RR R3, MR9,14   MR 103 (6)
Progeny 4401 RR       103 (6)
Delta King DK4866RR RR/STS MR3     103 (6)
Delta King DK4967RR RR R3, MR6,14   MR 103 (6)
Asgrow AG4801 RR R3   R 103 (7)
S. States RT4980 RR       103 (6)
Pioneer 94B73 RR     R 103 (9)
Other promising new varieties (tested in less than 6 locations)
S. States RT4451N RR R3,14     114 (4)
USG 7415nRR RR MR3     110 (4)
USG 7423nRS RR/STS R3, MR14   R 110 (4)
Pioneer 94M30 RR MR3   R 110 (3)
Asgrow AG4404 RR/STS       109 (3)
Vigoro V49N6RR RR R3   MR 109 (3)
USG 7455nRR RR R3,MR14   MR 108 (3)
NK S43-B1 RR R3, MR14     108 (4)
Vigoro V44N6RR RR R3, MR14   R 107 (4)
Vigoro V41N6RR RR       107 (3)
T.A. Seed TS4659 RR R3,14     106 (3)
Pioneer 94M50 RR R3, MR14   R 105 (3)
Asgrow AG4503 RR     R 105 (3)
Delta King DK4366RR RR       104 (3)

Table 9.1.7. Average relative yield of maturity group IV soybean varieties grown double-crop and tested in at least 6 locations over the last three years (2003-2005).
    Herbicide Resistance Nematode Resist. Frogeye Leaf Spot Resist. Avg. Relative Yield (No. Locations)
Brand Variety Cyst Root Knot
D&PL DP4748S STS 109 (7)
S. States RT4502N RR R3,14 105 (9)
Vigoro V442NRR RR MR3,14 105 (11)
D&PL DP4331RR RR MR3 MR 104 (13)
Delta King DK4461RR RR R5, MR2 MR 103 (6)
D&PL DP4690RR RR 103 (13)
Garst 4512RR/N RR 101 (6)
Other promising new varieties (tested in less than 6 locations)
USG 7495nRS RR/STS       121 (3)
Asgrow AG4903 RR/STS     MR 116 (5)
Vigoro V49N6RR RR R3   MR 111 (4)
S. States RT4151N RR R3,14     111 (3)
S. States RT4981N RR R3,14     110 (4)
Vigoro V50N6RR RR       110 (3)
Dyna-Gro 3443NRR RR MR3,14     107 (3)
Asgrow AG4801 RR R3   R 107 (5)
Pioneer 94M80 RR MR3,14   MR 106 (3)
S. States RT4651N RR R3,14     104 (3)
S. States RT4451N RR R3,14     104 (3)

Table 9.1.8. Average relative yield of maturity group V soybean varieties grown full-season and tested in at least 6 locations over the last three years (2003-2005).
    Herbicide Resistance Nematode Resist. Frogeye Leaf Spot Resist. Avg. Relative Yield (No. Locations)
Brand Variety Cyst Root Knot
USG 5002T       R 112 (9)
Virginia V98-9005         110 (10)
Public Teejay         108 (15)
USG 7524nRR RR R3   MR 107 (6)
Virginia V98-2711         107 (15)
USG 7553nRS RR/STS MR3,14   MR 107 (9)
Asgrow AG5603 RR R3     106 (10)
Asgrow AG5605 RR/STS MR3,14   MR 106 (12)
USG 5601T       R 105 (15)
S. States RT5450N RR R3,14     105 (8)
S. States SS5200STS STS       102 (8)
D&PL DP5110S STS       102 (9)
Delta King DK5967RR RR MR3,14 MRi   102 (6)
Other promising new varieties (tested in less than 6 locations)
Delta King DK5066RR RR R3, MR14   MR 109 (3)
Progeny 5822 RR       108 (5)
Progeny 5660 RR       102 (5)
Vigoro V51N6RR RR R3   MR 101 (4)

Table 9.1.8. Average relative yield of maturity group V soybean varieties grown double-crop and tested in at least 6 locations over the last three years (2003-2005).
    Herbicide Resistance Nematode Resist. Frogeye Leaf Spot Resist. Avg. Relative Yield (No. Locations)
Brand Variety Cyst Root Knot
S. States SS5200STS STS       114 (6)
Virginia V98-2711         109 (11)
Virginia V98-9005         109 (7)
Public Teejay         107 (11)
Public Hutcheson         105 (11)
D&PL DP5634RR RR R1,3 MRa MR 104 (10)
S. States RT5130N RR R3,14     104 (7)
USG 5601T       R 103 (11)
S. States RT5450N RR R3,14     103 (6)
S. States RT5540N RR R3,14     102 (6)
Vigoro V53N5RS RR/STS R3,MR14   R 102 (7)
D&PL DP5110S STS     MR 102 (6)
Vigoro V55N5RR RR R3,MR14   MR 101 (7)
Other promising new varieties (tested in less than 6 locations)
Asgrow AG5605 RR MR3,14   MR 111 (3)
USG 540nRR RR MR3,14   MR 109 (5)
USG 7505nRR RR R3   MR 106 (3)
USG 7553nRS RR/STS MR3,14   MR 106 (3)
Vigoro V51N6RR RR R3   MR 105 (4)
USG 7515nRS RR/STS R3, MR14     104 (3)

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2005 Virginia Soybean Yield Contest Entries

Producer County Brand & Variety Yield (bu/acre)
John Davis Caroline Garst 4212RR/STS/N 77.5
Robert Newcomb Hanover Pioneer 94B73 74.7
James Lee, IV Southampton Southern States RT 5450N 74.2
Eldon Horst Rockingham Pioneer 93M90 72.4
John Hula Henrico UniSouth Genetics USG 7423nRS 70.8
Ted Haberland Orange DeKalb DKB44-51 68.3
David Fitzgerald Augusta Pioneer 94B13 67.1
Lyndon Diehl Rockingham Pioneer 94M70 65.7
Bernard Yancey Rockingham Pioneer 94B13 63.4
Marty Diehl Rockingham Pioneer 94B13 61.4
Mark Deavers Rockingham Pioneer 94B13 61.1
Ronnie Russell Middlesex Pioneer 9492 60.7
Garland Martin Augusta Pioneer 93M92 56.8
Lyndon Diehl Rockingham Pioneer 94M70 51.1
Eugene King Rockingham Pioneer 93M92 43.9

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Sincerely,

David L. Holshouser


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