Weed Control in Soybean

Transcription

1 Weed Control in Soybean A Cautionary Tale Rob Gulden

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3 Biology of Soybean Cool-season legume, BUT behaves like a warmseason plant Ecologically not well adapted to the prairies Not very competitive with cool-season weeds

4 Maximum Root Depth (cm) Soybean Biology 0 Soybean Vol. Canola Slow biomass accumulation 5 10 Slow soil exploration (17C Root Isocline)

5 Corn Corn-Silage Soybean Barley Wheat Flax Oats Sorghum Proso Millet Buckwheat Dry Beans Sunflower Mustard Canola

6 Traditional Weed Management Programs Pre-Plant (PP), Pre-Plant Incorporated (PPI) or Preemergence (PRE) Soil-Residual Herbicide In-crop Rescue treatment when needed

7 Challenges with PP-, PPI- or PRE-Herbicides Need appropriate temperatures to work well Can be used on specific soils only Need Rain Activation Limited Weed Spectrum Variable Crop Tolerance Carry-Over Issues

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9 Critical Weed Free Period 1 st 3 rd trifoliate (Cowborough, OMAFRA)

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11 Glyphosate use in the US courtesy of Mike Owen

12 2008 courtesy of Mike Owen

13 Soybeans in a common waterhemp field courtesy of Mike Owen

14 courtesy of Mike Owen

15 courtesy of Mike Owen

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17 Chemical Fallow courtesy of I. Kristjanson

18 courtesy of I. Kristjanson

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24 Intensity of Soil Disturbance Zero Tillage Tine Harrow Tandem Disc Fall Seeding

25 Zero tillage Fall Emergence (before snowfall) Zero tillage & fall seeding Early fall tillage Early fall harrow Early fall harrow & fall seeding Late fall tillage Late fall harrow

26 Emerged Volunteer Canola Seedlings (m -2 ) Fall Emergence A Kelburn, MB Carman, MB B C Melita, MB 8000 C D c Zero Tillage b b C B AB A B Zero Tillage + Seeding Harrow a Harrow + Seeding b D c C D Tillage Harrow Tillage c C Early Fall Soil Disturbance Treatments Late Fall

27 Seedbank (Seeds m -2 ) Emergence (Seedlings m -2 ) A A-C BC B-E AB BC C DE C E Spring Seedbank Spring Emergence BC C-E A-C A-D Zero Tillage Zero Tillage + Seeding Harrow Early Fall Harrow + Seeding Tillage Harrow Tillage Late Fall 0 Soil Disturbance Treatments

28 Seed (kg ha -1 ) Row Spacing Soybean Yield Volunteer Canola Seed Return 1600 BC C-E C-E A A A " 15.0" 30.0"

29 Seed (kg ha -1 ) Soybean Yield Volunteer Canola Seed Return A C-E Seeding Rates kg ha A AB kg ha " 7.5" 1.5X Seeding Rate

30 30 (glyphosate) 30 Inter-row tillage 30 wheat inter-row mulch (glyphosate) 30 fall rye inter-row mulch (glyphosate)

31 Seed (kg ha -1 ) Inter-Row Weed Management Soybean Yield A Volunteer Canola Seed Return AB BC C-E B-E C-E C-E A BC BC A BC C C " 15.0" Wheat Inter-row Mulch 15.0" Fall rye Inter-row Mulch 30.0" 30.0" Wheat Inter-row Mulch 30.0" Fall rye Inter-row Mulch 30.0" Inter-row Tillage

32 Threshold studies 0 seeds m seeds m seeds m seeds m seeds m seeds m seeds m seeds m -2

33 Yield Loss (%) 80 Melita Wide I = 2.93 A = Narrow I = 4.91 A = Canola Density (plants m -2 )

34 Action Threshold (5% Yield Loss) Site Year Action Threshold Plants m -2 Year Location Narrow Wide 2012 Carman Carman Kelburn Kelburn Melita Melita MEAN SEM Action Threshold = Y L *A (I * A) (I * Y L )

35 Canola Seed Action Threshold (5% Yield Loss) Site Year Canola Seed Return g m -2 (bu/ac) Year Location Narrow Wide 2012 Carman Carman 28.6 (5.1) 42.4 (7.6) 2012 Kelburn 27.1 (4.8) 50.7 (9.0) 2013 Kelburn 37.6 (6.7) 47.8 (8.5) 2012 Melita 13.7 (2.4) 37.0 (6.6) 2013 Melita 61.5 (11.0) 59.7 (10.6) MEAN 33.7 (6.0) 47.5 (8.5) SEM 7.9 (1.4) 3.8 (0.7)

36 5.4 plants m plants m plants m -2 Volunteer canola in wide row soybean

37 Herbicide work on volunteer canola PRE herbicides alone POST herbicides alone PRE + POST herbicide combinations POST options for Extend soybean PRE options for Enlist soybean

38 Herbicide options for GR vol. canola PRE Roundup Heat Express Valtera Florasulam First Rate 2,4-D ester Focus POST Roundup Cadet First Rate Reflex Thifensulfuron Basagran Forte Viper ADV Odyssey Solo

39 Take Home Message Early weed control in soybean is critical / manage herbicideescapes immediately Scout intensely for new weeds and resistant biotypes throughout the cropping season Volunteer canola is often more of an aesthetic problem than an economical one, but numerous herbicide options available Incorporate strategies to take pressure off herbicides to ensure long-term sustainability of soybean production systems Expect weed species shifts and new weeds to become problematic

40 Acknowledgements Collaborators: Dr. Willenborg, U of S Grad students: Paul Gregoire Charles Geddes ADF Technical assistance: Derek Lewis Becky Dueck many summer students