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Fluctuations of the weed seedbank at the long-term Beltsville Farming Systems Project

Fluctuations of the weed seedbank at the long-term Beltsville Farming Systems Project. John R. Teasdale Ruth W. Mangum Jay Radhakrishnan Michel A. Cavigelli USDA-ARS Beltsville, Maryland, USA. Farming Systems Project 1996-2002. Systems

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Fluctuations of the weed seedbank at the long-term Beltsville Farming Systems Project

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  1. Fluctuations of the weed seedbank at the long-term Beltsville Farming Systems Project John R. Teasdale Ruth W. Mangum Jay Radhakrishnan Michel A. Cavigelli USDA-ARS Beltsville, Maryland, USA

  2. Farming Systems Project 1996-2002 • Systems • Recommended inputs – Two year Corn-Wheat/Soybean • Reduced inputs – Two year Corn-Wheat/Soybean • Organic – Two year Corn-Soybean (CS) • Organic – Three year Corn-Soybean-Wheat/fallow (CSW) • Organic – Four year Corn-Soybean-Wheat/Hay-Hay (CSWH)

  3. Species b0 bc bc2 bn bcn R2 • A. hybridus 902 911 -5.84 -0.702 -0.0159 0.629 • C. album 1259 245 +3.15 -0.347 -0.0051 0.613 • An. grasses 1054 371 +1.78 -0.541 -0.0404 0.809 Multiple Regression Model D = b0 + bcC + bc2C2 + bnN + bn2N2 + bcnCN where D = annual seedbank change C = percent weed cover at maturity N = seedbank in spring

  4. Amaranthus hybridus annual seedbank change • High weed cover leads to large seedbank increase at low initial seedbank. • High initial seedbank leads to potential large seedbank decrease. • Equilibrium defined by horizontal plane through seedbank=0.

  5. Conditions with no annual seedbank change (intersection between response surface and plane at seedbank=0)

  6. Annual weed seedbank dynamics at FSP Extreme drought in 1999 No seed production Poor control High seed production Implication: Seedbank can be reduced rapidly by management if no seed production

  7. Mean over 1997-2002 Seedbank of Major Weed Species Longer, more phenologically diverse organic rotations reduced the weed seedbank

  8. Lowering the seedbank by using more diverse rotations can improve weed control in organic corn

  9. Regression R-squared Year A. hybridus C. album Grass 1997 0.081 0.392 0.053 1998 0.572 0.532 0.502 2000 0.041 0.468 0.002 2001 0.757 0.014 0.700 Relation between weed cover at maturity and spring seedbank for major species in corn

  10. Role of Sequence: Three Rotations - All starting Corn-Soybean Rotation had little influence when start with corn

  11. Role of Sequence: Four Year Rotation – Different starting crops Starting rotation with hay reduced seedbank

  12. Seedbanks in organic systems • Fluctuated according to level of seed inputs • Rapid decline with no seed inputs suggests can reduce seedbank quickly through management • Rotations with higher phenological diversity can reduce seedbank • Rotation sequences beginning with hay are better than sequences beginning with corn • Lower initial seedbank can increase success of weed control in corn

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