Washington State University Puyallup
  Organic Farming Systems and Nutrient Management


Organic Farming Systems

This experiment is on organically certified research land, and includes only organic treatments. 

In 2003 we established an organic vegetable production systems experiment on organically certified research land at WSU Puyallup. The experiment compares 12 organic management systems, including three cover cropping systems, 2 tillage treatments, and 2 amendment types, arranged in a split-split plot design. Treatments were chosen based on input from local farmers through workshops, farm visits, surveys, and focus groups.

plot map

Photo Organic Farming Plots

Crop rotation: Single crops (outlined in purple above) were grown the first three years of the experiment, including snap bean (2003), fall spinach following summer cover (2004), and winter squash (2005). Beginning in 2006, four rotation crops are grown within each plot each year, including snap bean, winter squash, and spring broccoli followed by fall spinach.

 

Treatments: The treatments include three cover crops, two tillage systems, and two organic amendments.

  **Cover crops (main plots)
  • Fall planted cereal-legume mix (currently cereal rye-hairy vetch).
  • Summer planted legume as a relay crop between rows of the cash crop (currently hairy vetch).
  • Fall planted grass-legume mix managed as pasture for one growing season before incorporation the following growing season (currently annual ryegrass-perennial ryegrass-red clover). This treatment is planted to cash crops in 2003, 2005, and 2007. Pastured poultry were raised on these plots in 2006. 
**Tillage to prepare ground (split plots)   
  • Conventional: Major tillage done with plow, disc, and rototiller as needed.
  • Spader: Major tillage done with a spader. This usually prepares a seedbed in a single pass.
**Amendments (split-split plot):
  • Broiler litter; low C:N ratio, low application rate (average 2 dry tons/acre). The broiler litter is piled, self-heated to at least 131 F and turned 5 times to meet organic standards for pathogen reduction.
  • On-farm compost; medium C:N ratio, high application rate (average 15 dry tons/acre). The on-farm compost consists of broiler litter, yard debris, separated dairy solids, and bedding from the local fair. It is composted in a static pile (actively aerated for 4-6 weeks), then passively cured for 5 months, with temperatures monitored to meet organic standards.

 

Measurements:

 
  • Crop yield and quality
  • Soil organic matter, pH, soil test nutrients 
  • Soil nitrate (early season, mid-season, and post harvest)
  • Cover crop yield
  • Soil physical measurements (aggregate stability, bulk density, compaction, infiltration)
  • Soil biological quality (collembola, nematodes, PLFA, selected enzymes and substrate-induced respiration)
  • Insect pests
  • Weed ecology (weed biomass and/or counts and major species)
  • Production costs and value

 

Results: 2007 Data on Soil Quality and Yields for this experiment are found in the Soil Quality Progress Report Page

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