Organic Transition Rotations for Northwestern Washington

Two three-year rotations are being investigated for suitability for organic transition in northwestern Washington. Cover crop growth was greater and resulted in better weed suppression during 2004-05 than in 2003-04. Common chickweed was the major winter weed species, accounting for 90% of the total weed biomass during the first winter and 75% during the second. Mid-summer weed growth was greater during 2005 and 2006 than 2004. The infrared flamer provided effective postemergence weed control, although spinach and broccoli foliage were damaged. Vinegar and clove oil in shielded applications beside the crop row were less effective than flaming. Broccoli provided the poorest weed suppression in two of three years, followed by spinach/cucumber and potato in 2004 and by potato, spinach, and cucumber in 2005. In 2006, spinach seed was the poorest competitor with weeds, followed by potato and cucumber/broccoli. Mustard cover cropping prior to growing potatoes increased disease severity in 2004, particularly for compost-treated potatoes compared to potatoes receiving fish fertilizer (9.4 and 6.9% severity, respectively). Although scab severity was fairly low in 2004 (<10% regardless of fertilizer type), disease incidence in potatoes following a mustard cover crop averaged about 57%, compared to approximately 45% in potatoes following a rye + buckwheat cover crop.

Grant Information

  • Project ID: 005
  • Project Status: Complete


  • Principal Investigator(s): Inglis, D., Miller, T.
  • Grant Amount: $18,670


  • Principal Investigator(s): Inglis, D., Miller, T.
  • Grant Amount: $30,959


  • Principal Investigator(s): Inglis, D., Miller, T.
  • Grant Amount: $31,980