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SMACKDOWN: TRAITED VS. CONVENTIONAL SOYBEAN VARIETY PERFORMANCE Shawn P. Conley, John Gaska, and Mark Martinka 1/ Soybean seed price will continue to be a major driver of seed sales in 2011. Preliminary quotes on base seed price (minus discounts, seed treatment, and promotions) have ranged from the mid $30's (conventional) to the high-$50's (RR2Y®) on a per-bag, untreated basis. Growers are also challenged with a multitude of seed treatment offerings that not only confound variety selection, but also significantly increase seed price. Such a huge discrepancy in price and seed treatment options has growers struggling over their 2011 variety selection decisions. Since 2003, we have seen a divergence in soybean yield potential between conventional and Roundup Ready (RR®) soybean varieties in our WI trials. To further characterize these yield differences and test the yield potential of LL® soybean, we included several high yielding RR®, RR2Y®, and LL® soybean varieties as checks in our conventional and traited herbicide trials in 2010. Additionally, using our existing glyphosate resistant soybean variety trials, we can directly compare the yield of RR® and RR2Y® varieties. This information provides growers with yield and economic comparison among the different soybean traits offered. Roundup Ready Soybean Tests Averaged across all varieties that carried either the RR® or RR2Y® trait in our glyphosate resistant soybean variety trials, RR2Y® significantly out-yielded RR® by 1.2 to 2.8 bu/acre in our Southern, Central, and North-Central testing regions (Fig. 1). Within each region however there were both high yielding (starred) RR® and RR2Y® variety offering for growers, suggesting that through careful variety selection, high yielding varieties are available that may be less costly. Conventional and Traited Herbicide Soybean Tests In our Southern tests (two locations), we found high yielding varieties in all the LL®, RR®, RR2Y®, and conventional herbicide soybean categories (Please see Table 6 of the 2010 WI Soybean Variety Test Results: http://soybean.uwex.edu/soytrials/printable/index.cfm). Comparing yields between traits, and across two locations, RR2Y® out-yielded the other traits in the southern region (Fig. 2a). In contrast, at our N. Central conventional and traited herbicide soybean test, we found high yielding varieties in the RR®, RR2Y®, and conventional herbicide soybean categories (Please see Table 7 of the 2010 WI Soybean Variety Test Results). However, averaged across varieties RR2Y® traited varieties out-yielded both RR® traited and conventional soybean varieties and were equal to LL® in the North Central test (Fig. 2b). These results, further suggest that growers have many high yielding options available to them among and across traits in all regions of WI. Based on the yield potential and variable costs including seed price, seed treatment, and herbicide management program, it is critical for growers to conduct a thorough economic analysis prior to purchasing seed of any conventional or traited variety. To aid in this decision making process, we recommend using Dr. Joe Lauer's Crop Seed Price Calculator found at (http://corn.agronomy.wisc.edu/Season/DSS.aspx). This tool allows growers to directly compare varieties based on yield potential, seed price, seed treatment or herbicide management program. ______________________ State Soybean Specialist, Outreach Specialist, and Soybean Variety Trial Program Manager, respectively, Dept. of Agronomy, 1575 Linden Dr., Univ. of Wisconsin-Madison, Madison, WI.

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Proc. of the 2011 Wisconsin Crop Management Conference, Vol. 50

Figure 1. Soybean yield comparison between RR® and RR2Y® soybean traits in the 2010 WI Southern, Central, and North-Central Roundup Ready soybean tests.

2010 Southern Region Average Yields

80 P value = 0.004 ; + 1.4 bu 75

75 80 P value = 0.007 ; + 1.2 bu

2010 Central Region Average Yields

70

70

Yield Bu/A

Yield Bu/A

65

65

60

60

55

55

50 RR1 (48/77 Varieties) RR2Y (29/77 Varieties)

50 RR1 (34/67 Varieties) RR2Y (33/67 Varieties)

Trait

Trait

2010 North-Central Region Average Yields

70 P value < 0.0001 ; + 2.8 bu 65

60

Yield Bu/A

55

50

45

40 RR1 (26/52 Varieties) RR2Y (26/52 Varieties)

Trait

Figure 2. Soybean yield comparison between RR®, RR2Y®, , LL®, and conventional, , soybean traits in WI 2010 Southern (2a) and North Central (2b) Conventional and Traited herbicide tests.

2010 Southern Conventional and Traited Herbicide Test

80 P value < 0.0001 75

2010 N. Central Site Conventional and Traited Herbicide Test

70 P value < 0.0001 65

2a A

2b

70

B

B

60

A AB

Yield Bu/A

65

C

Yield Bu/A

55

BC

C

60

50

55

45

50 RR1 (5/44) RR2Y (6/44) LL (8/44) Conv (25/44)

40 RR1 (3/38) RR2Y (7/38) LL (4/38) Conv (24/38)

Trait

Trait

Proc. of the 2011 Wisconsin Crop Management Conference, Vol. 50

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Traited vs. Conventional Soybean Variety Performance

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