Flax Tolerance to Preemergence Herbicides
P. Hendrickson

The study was conducted on a Heimdal silt loam soil with a 7.5 pH and 2.7% organic matter.  Flax (Cathay) was seeded on May 7th at 41 lbs/A.  PRE herbicides were applied immediately after planting with 560 F air, 480 F soil, 60% relative humidity, 5% clouds, and no wind.  The soil surface was dry to a depth of 0.75 inches.  Treatments were applied to 8-by 25-ft plots with a hand-boom calibrated to deliver 20 gpa at 20 psi through XR8003 flat fan nozzles.  The trial was harvest with a plot combine on August 24, 2000.  The experimental design was a randomized complete block with three replicates.

Weeds evaluated were common lambsquarters, redroot pigweed, and prostrate pigweed.  Both sulfentrazone and flumioxazin provided excellent control of common lambsquarters, redroot pigweed, and prostrate pigweed.  DPX-R6447 applied at 0.125 lb ia/A provided excellent common lambsquarters and redroot pigweed control, but was weak on prostrate pigweed. 

Weed control in flax.                  
Weed control Flax
5/30/00 6/20/00 5/30/00 5/30/00 6/20/00 7/17/00 8/24/00
Treatment Rate CHEAL1 AMARE2 CHEAL AMARE AMABL3   stand counts

injury

yield
Lb ia/A

---------------------  %   ----------------------

# / 3 m of row

----------  % -----------

lbs/A
sulfentrazone 0.125 98 95 94 96 83 267 17 7 0 24
sulfentrazone 0.25 100 98 99 100 95 239 33 20 0 24
sulfentrazone 0.5 100 100 100 100 100 180 70 60 33 21
flumioxazin 0.0938 95 96 92 98 93 236 30 13 0 24
flumioxazin 0.1875 98 100 98 100 100 181 53 50 33 20
DPX-R6447 0.0625 88 88 75 80 53 266 13 5 0 23
DPX-R6447 0.125 96 97 90 88 67 229 27 10 13 24
check 0 0 0 0 0 0 276 0 0 0 18
LSD (0.05)   7 5 6 4 12   57 10 12 5 3
1CHEAL = common lambsquarters (Chenopodium album)
2AMARE = redroot pigweed (Amaranthus retroflexus)
3AMABL = prostrate pigweed (Amaranthus blitoides)

All treatments, except the high rate of sulfentrazone and flumioxazin, had yields greater than the untreated check.  Both the high rate of sulfentrazone and flumioxazin caused significant crop injury and reduction in plant stand counts (Table). 

 
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Experiment Station
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