Table 21. Estimated Yield Reduction From Various Weed species in Corn and Soybeans

 

  Percent Corn Yield Reduction Percent Soybean Yield Reduction
  1 2 4 6 8 10 1 2 4 6 8 10
  Weeds/100 Ft of Row Weeds/100 Ft of Row
C. Cocklebur 4 8 16 28 34 40 1 2 4 6 8 10
Redroot Pigweed or
C. Lambsquarters		 12 25 50 100 125 150   4 6 10 15 20
Shattercane
(2-3/clump)		 6 12 25 50 75 100   5 8 11 14 17
Giant foxtail 15 30 60 85 175 400   25 80 300 400 600
Velvetleaf or
A. Morningglory		 10 15 20 30 40 50   3 6 10 13 16
Penn. Smartweed or Jimsonweed - - - - - - 2 4 6 10 15 20
Yellow Nutsedge 400 800 + + + + - - - - - -
Volunteer Corn - - - - - - 1 2 3 4 5 6
- Signifies that no data is available

Corn example: We scout a corn field and find an average of 28 cocklebur and 50 pigweed per 100 feet of corn row. This density of cocklebur and pigweed causes a 6 percent and 4 percent yield loss, respectively. By adding the two respective yield losses together, we calculate a total yield loss of 10 percent. Fill in the blanks below with the other necessary variables to calculate the feasibility of treatment.

Soybean example: We scout a soybean field and find an average of 8 giant ragweed, 25 velvetleaf, and 10 giant foxtail clumps per 100 feet of row. This translates into an 8 percent, 4 percent, and 2 percent potential yield loss, respectively. Once again, by summing the values we might expect a total yield loss of 14 percent.

Expected yield 150 bu/A Expected yield 40 bu/A
Percent loss 10% = 15 bu/A Percent loss 14% = 5.6 bu/A
Expected loss $37.50/A Expected loss $33.60/A
  @$2.50/bu   @$6.00/bu
Est. treatment cost $10.00/A Est. treatment cost $22.00/A
Net gain of treatment $27.50/A Net gain of treatment $11.60/A

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