Washington State Organic Systems Trial
Posted: November 6, 2013
Dr Craig Cogger, WSU Pyallup shows nifty harvest platform which helps keep flats off the ground for food safety.
The WSU farming systems trial was inspired by local grower needs. Researchers conducted a series of listening sessions for small scale, direct market growers. “We found out what small scale growers were interested in,” Craig explained. Then they designed treatments to look at those aspects.
The trial looked at tillage, cover crops and amendments and measured soil quality indicators and yield for broccoli, lettuce, spinach and winter squash. In organic systems we often rely on a lot of tillage and cultivation. To reduce tillage impact they trialed a spader and compared it to disking and rototilling. A spader has multiple spades which mimic the action of hand digging instead of churning the soil like a rototiller. They found they were able to till a little deeper with the spader and there was less compaction. Yields were also better in some years, likely due to reduced compaction. “Spaders are expensive and you have to drive more slowly,” Craig explained, “But we were able to reduce our passes, have less compaction, and increase yields in three of ten years.”
Researchers also compared amendments. Compost had a lower nitrogen content so they put it on at a higher rate than composted broiler manure. Where they added more organic material and carbon from the compost they were able to increase their organic matter, and increase water infiltration. Craig says the take home message is, “If you are starting up in the organic world, add as much organic material as you can within your nutrient limitations in the first few years. Then you can slow down and rely on cover crops and less frequent applications.”
I found the cover crop comparison one of the most interesting aspects. Not only did they look at annual cover crops including rye and vetch, and cover crops inter-seeded between vegetable rows. They also worked with a pasture rotation. In this system vegetables were rotated with a mix of annual and perennial ryegrass and clover, which was maintained as pasture for thirty months. Pastured broilers went through plots one time per year and sheep were on a 7-10 day grazing rotation schedule between April and September. As expected the rye/ vetch blend did well, though with cold wet springs they have to adjust the percentage of rye out west compared to what we use in the east. Pasture as a cover crop rotation did well for winter squash and lettuce where yields were comparable to cover cropped plots. But this low input system did not have enough nitrogen for broccoli.
From research station to the farm:
Washington farmers are taking this new research the next step. For example Kirsop Farm has been producing pasture poultry on their farm. They have also worked with cover crop interseeding, not only spinning it on at last culitivation like they do for carrots and lettuce at the Puyallup station but also working with strips of clover in wider crop spacing.
Learning from our mistakes:
I always like to know what doesn’t work as well as what works. No sense in repeating an experiment that is doomed. Craig says one thing that did not work well in their trials was inter-seeding into high shade crops like winter squash. They just did not establish well.
Craig and others are also studying food safety and greenhouse gasses. They can use their living laboratory with the legacies of different long term organic management techniques to compare irrigation water treatment and application for food safety, and organic management effects on nitrous oxide emissions.