Weed management in alfalfa<br />Mark J. Renz<br />mrenz@wisc.edu<br />University of Wisconsin-Madison<br />
Costs of weeds in forages<br /><ul><li>Risk of establishment failure
Reduction in biomass of desirable plants (FEED)
Reduction in quality of feed
Affect animal health</li></ul>Poison<br />Reduced feeding<br />
Impact of Common Weeds on Forage Quality<br />	SERIOUS	MODERATE	SLIGHT<br />ANNUAL WEEDS                                  ...
Weed Management in the Establishment Year<br /><ul><li>Weed management decisions should be based on </li></ul>weed species...
Methods of establishing alfalfa<br /><ul><li>Direct seeding
Spring
Late summer
Seeding with a companion crop</li></li></ul><li>Reduction in alfalfa plant density from weed competition<br />
Reduction in alfalfa plant density from weed competition<br />
55 stems/square foot= 4-5 plants/square foot<br />
Goal is for >30 plants/square foot by fall<br />
Effects of seeding rate when don’t control weeds<br />
Summary for establishment effects on alfalfa density<br />Weeds can reduce stand density<br />Be careful especially if pla...
When should we manage weeds in Alfalfa?<br />
Critical period Period of time after crop emergence that will not have yield reduction if weeds are removed<br />% alfalfa...
Critical period <br />Note can change if more weeds!<br />% alfalfa yield (vs no weeds)<br />
Results<br /><ul><li>Critical period varied by location but ranged between 1st and 7thtrifoliate leaf
3-5 weeks after planting
1-5 weeks after planting
Same period was found for first harvest and first year yield of ALFALFA ONLY
Higher weed density caused critical period to begin earlier</li></li></ul><li>What effect will weed management have on for...
Yield changes from weed removal<br />
Yield changes from weed removal<br />
Yield differences in establishment year5 states including Wisconsin<br />
Forage quality (RFV) changes from weed management<br />Can reduce RFV below recommendations for Dairies<br />Depends on th...
Impact of Common Weeds on Forage Quality<br />	SERIOUS	MODERATE	SLIGHT<br />ANNUAL WEEDS                                  ...
Summary for establishment<br />Weeds can be costly in establishment year<br />Can reduce stand density<br />Increase forag...
earlier if high weed density
Gains in forage quality and stand establishment, not tonnage</li></li></ul><li>Should I be concerned about weeds in late s...
Controlling volunteer wheat in summer seeding alfalfa<br />alfalfa no-till drilled at 13 lbs/A<br />8/18/2008<br />8/15/20...
Response of alfalfa density and yield from volunteer wheat 2008-09 = 12- 49  plants/ft22009-10 = 7-94 plants/ft2<br />4-5 ...
Response of alfalfa density and yield from volunteer wheat <br />
Does volunteer wheat reduce establishment and yield?<br />ESTABLISHMENT: Yes; 3 to 5 more plants/ft2 in untreated plots th...
SUMMARY FOR NEW SEEDLINGS<br /><ul><li>Base weed management decisions on
weed species and density
soil moisture
Need for high quality forage
Many herbicide options available
Scout carefully for </li></ul>weed species/density<br />Alfalfa density/stand establishment<br />
WEED MANAGEMENT IN ESTABLISHED MIXTURES<br />Different than seeding year as forages are well established and competitive<b...
Yellow Rocket and Forage Quality<br /><ul><li>Reduces protein content 2 to 3% compared to alfalfa
Reduces digestibility and feed value</li></li></ul><li>Dandelions and Protein Content<br /><ul><li>Reduce protein in first...
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Weed management in alfalfa

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  1. 1. Weed management in alfalfa<br />Mark J. Renz<br />mrenz@wisc.edu<br />University of Wisconsin-Madison<br />
  2. 2. Costs of weeds in forages<br /><ul><li>Risk of establishment failure
  3. 3. Reduction in biomass of desirable plants (FEED)
  4. 4. Reduction in quality of feed
  5. 5. Affect animal health</li></ul>Poison<br />Reduced feeding<br />
  6. 6. Impact of Common Weeds on Forage Quality<br /> SERIOUS MODERATE SLIGHT<br />ANNUAL WEEDS .<br />YELLOW FOXTAIL GREEN FOXTAIL COMMON RAGWEED<br />GIANT FOXTAIL VELVETLEAF PIGWEED SPECIES<br />GIANT RAGWEED SHEPHERD’S PURSE <br />SMARTWEEDS PENNYCRESS <br />COCKLEBUR LAMBSQUARTERS<br />NIGHTSHADES WILD MUSTARD<br />PERENNIAL WEEDS .<br />CURLY DOCK CANADA THISTLE DANDELION<br />HOARY ALYSSUM QUACKGRASS WHITE COCKLE<br />YELLOW ROCKET <br />
  7. 7. Weed Management in the Establishment Year<br /><ul><li>Weed management decisions should be based on </li></ul>weed species <br />weed density<br />soil moisture <br />IFweed density is moderate to low <br />AND soil moisture is adequate <br />THEN successful establishment<br />
  8. 8. Methods of establishing alfalfa<br /><ul><li>Direct seeding
  9. 9. Spring
  10. 10. Late summer
  11. 11. Seeding with a companion crop</li></li></ul><li>Reduction in alfalfa plant density from weed competition<br />
  12. 12. Reduction in alfalfa plant density from weed competition<br />
  13. 13. 55 stems/square foot= 4-5 plants/square foot<br />
  14. 14. Goal is for >30 plants/square foot by fall<br />
  15. 15. Effects of seeding rate when don’t control weeds<br />
  16. 16. Summary for establishment effects on alfalfa density<br />Weeds can reduce stand density<br />Be careful especially if planting <br />Planting lower alfalfa densities<br />Have high weed pressure<br />Competitive weeds species in field<br />Dry conditions that reduce alfalfa emergence<br />Management can alleviate some of the loss<br />Many tools available<br />Allow for scouting and POST application<br />
  17. 17. When should we manage weeds in Alfalfa?<br />
  18. 18. Critical period Period of time after crop emergence that will not have yield reduction if weeds are removed<br />% alfalfa yield (vs no weeds)<br />
  19. 19. Critical period <br />Note can change if more weeds!<br />% alfalfa yield (vs no weeds)<br />
  20. 20. Results<br /><ul><li>Critical period varied by location but ranged between 1st and 7thtrifoliate leaf
  21. 21. 3-5 weeks after planting
  22. 22. 1-5 weeks after planting
  23. 23. Same period was found for first harvest and first year yield of ALFALFA ONLY
  24. 24. Higher weed density caused critical period to begin earlier</li></li></ul><li>What effect will weed management have on forage yield and quality?<br />
  25. 25. Yield changes from weed removal<br />
  26. 26. Yield changes from weed removal<br />
  27. 27. Yield differences in establishment year5 states including Wisconsin<br />
  28. 28. Forage quality (RFV) changes from weed management<br />Can reduce RFV below recommendations for Dairies<br />Depends on the weed species and weed density!<br />
  29. 29. Impact of Common Weeds on Forage Quality<br /> SERIOUS MODERATE SLIGHT<br />ANNUAL WEEDS .<br />YELLOW FOXTAIL GREEN FOXTAIL COMMON RAGWEED<br />GIANT FOXTAIL VELVETLEAF PIGWEED SPECIES<br />GIANT RAGWEED SHEPHERD’S PURSE <br />SMARTWEEDS PENNYCRESS <br />COCKLEBUR LAMBSQUARTERS<br />NIGHTSHADES WILD MUSTARD<br />PERENNIAL WEEDS .<br />CURLY DOCK CANADA THISTLE DANDELION<br />HOARY ALYSSUM QUACKGRASS WHITE COCKLE<br />YELLOW ROCKET <br />
  30. 30. Summary for establishment<br />Weeds can be costly in establishment year<br />Can reduce stand density<br />Increase forage quantity (1st and maybe 2nd cutting)<br />Weeds cause the increase<br />Reduce forage quality (1st and maybe 2nd cutting)<br />Depends on the weed species<br />Management can reduce impact of weeds<br /><ul><li>Critical period 3-5 weeks after planting
  31. 31. earlier if high weed density
  32. 32. Gains in forage quality and stand establishment, not tonnage</li></li></ul><li>Should I be concerned about weeds in late summer seedings?<br />Volunteer wheat in<br /> alfalfa, a growing<br /> problem in Wisconsin <br />
  33. 33. Controlling volunteer wheat in summer seeding alfalfa<br />alfalfa no-till drilled at 13 lbs/A<br />8/18/2008<br />8/15/2009 <br />Densities wheat<br />12-49 plants /ft2<br />7-94 plants /ft2<br />Mid September <br />Poast at 1.5 pt/A to ½ of the plots. <br />Wheat: 6-8 inches tall<br />Alfalfa<br />4-6 trifoliate leaves<br />4-5 inches tall<br />
  34. 34. Response of alfalfa density and yield from volunteer wheat 2008-09 = 12- 49 plants/ft22009-10 = 7-94 plants/ft2<br />4-5 plants/ft2 is minimum threshold, but would like to have 30 plants/ft2<br />
  35. 35. Response of alfalfa density and yield from volunteer wheat <br />
  36. 36. Does volunteer wheat reduce establishment and yield?<br />ESTABLISHMENT: Yes; 3 to 5 more plants/ft2 in untreated plots than treated.<br />YIELD: Total yield is higher in untreated (42-69%), but % alfalfa can be reduced. <br />FORAGE QUALITY: Untreated reduced quality needed for dairies.<br />
  37. 37. SUMMARY FOR NEW SEEDLINGS<br /><ul><li>Base weed management decisions on
  38. 38. weed species and density
  39. 39. soil moisture
  40. 40. Need for high quality forage
  41. 41. Many herbicide options available
  42. 42. Scout carefully for </li></ul>weed species/density<br />Alfalfa density/stand establishment<br />
  43. 43. WEED MANAGEMENT IN ESTABLISHED MIXTURES<br />Different than seeding year as forages are well established and competitive<br />Weed density typically low/absent <br />Base management decisions on legume legume stand density and forage quality<br /><ul><li>Weeds fill in gaps created by thinning stands</li></li></ul><li>Life History of Weeds of Concern in AlfalfaSurvey results from 285 PMU 2006<br />
  44. 44. Yellow Rocket and Forage Quality<br /><ul><li>Reduces protein content 2 to 3% compared to alfalfa
  45. 45. Reduces digestibility and feed value</li></li></ul><li>Dandelions and Protein Content<br /><ul><li>Reduce protein in first cutting only
  46. 46. No effect on digestibility or consumption</li></li></ul><li>Grass Protein Content<br />Alfalfa =<br />12-20%<br />
  47. 47. Treat or rotate crop?<br />Treat if weedy but have: <br /><ul><li>> 4 to 5 plants/sq. ft
  48. 48. >55 stems/sq. ft</li></ul>If below consider crop rotation <br />Do spring and fall alfalfa counts<br />
  49. 49. What herbicide options do I have during establishment?<br />
  50. 50. Pursuit or Raptor<br /><ul><li>Broad spectrum of control by both foliar and root uptake (sprayed post; acts pre as well)
  51. 51. Early postemergence application
  52. 52. Alfalfa with it’s second trifoliate leaf or >
  53. 53. Weeds 1 to 3 inches tall
  54. 54. Raptor better on lambsquarters + foxtails
  55. 55. Some injury can occur to alfalfa</li></ul>Can reach 20% yield reduction<br />
  56. 56. Roundup Ready alfalfa is now available!<br /><ul><li>Application timing: emergence - 5d before harvest
  57. 57. Each application:
  58. 58. no more than 1.5 lbsae/A
  59. 59. Over the entire year:
  60. 60. No more than 4.64 lbsae/A per year
  61. 61. Applications must be at least 7 days apart
  62. 62. glyphosate must be registered for use on RR alfalfa</li></li></ul><li>Timing of application for pursuit/raptor vs glyphosate<br />Few seedlings (< 10%) may not be Roundup resistant<br />Recommend application at 3-4 trifoliate leaf to eliminate these seedlings (22 fl oz/A)<br />Raptor/Pursuit<br />Roundup<br />
  63. 63. Costs and benefits of Roundup Ready alfalfa<br />Benefits: <br />herbicide is cheap<br />Roundup ($5-10) vs Pursuit/Raptor ($15-21)<br />Application timing is flexible to crop, but 1 application needed<br />Avoid potential yield loss from standard treatments<br />Can apply to larger weeds and eliminate<br />Control ALS resistant weeds<br />Convenient<br />Costs:<br />Expensive<br />$125/50 lbs bag technology fee<br />Seed costs will be 2x nonproprietary varieties<br />Will need to make a herbicide application<br />No residual weed control<br />May increase potential for glyphosate resistant weeds<br />Future litigation and regulation?<br />
  64. 64. RR Alfalfa Yield Trials in WI<br /><ul><li>Seeding year 0.25-0.77 tons d.m./acre yield advantage (6-16%) for using glyphosate compared to raptor
  65. 65. Subsequent total yield through the first three production years did not differ
  66. 66. There were significant differences in yield among the RR varieties</li></li></ul><li>Roundup Ready alfalfa<br />What we don’t know<br /><ul><li>How well will it work in no-till where difficult to control perennial weeds are present?</li></ul>Dock species, Canada thistle, hoary alyssum, white cockle<br /><ul><li>Fit with alfalfa/grass mixtures
  67. 67. Persistence in Wisconsin</li></ul>Data from Michigan suggests no increase in stand longevity<br />Current research monitoring stand density of older fields<br />
  68. 68. RR Calculator<br /><ul><li>Excel spreadsheet that compares cost of RR vs. conventional alfalfa.
  69. 69. Values are pre-entered that reflect Wisconsin’s the costs, use patterns, and yield.
  70. 70. User can change data specific for a field or farm and provide a more accurate analysis of the costs. </li></ul>http://www.uwex.edu/ces/forage/pubs/economics_RR_alfalfa.xls<br />
  71. 71. What ADDITIONAL herbicide options do I have in established crops?<br />* For common crops (Corn, Soybeans, wheat)<br />
  72. 72. Summary<br /><ul><li>Weed management is dependent on several factors </li></ul>weed species, weed density, market for forage, growing conditions……….<br /><ul><li>Herbicides typically improve forage quality, but rarely improve yield</li></ul>Establishing alfalfa:<br />Security against stand failure <br />Weed free, high quality forage first cut<br />Established alfalfa: Improved quality<br /><ul><li>Often weedy alfalfa fields are indications that the </li></ul>Crown density is below threshold rotated to another crop<br />
  73. 73. Questions?<br />mrenz@wisc.edu<br />

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