Manure bioassay setup.

I purchased a truckload of composted manure from a local farmer in the spring of 2018. When I planted the potatoes into it, the plants came up slowly, were stunted, and had curled, misshapen leaves. After researching online, I suspected that the manure was contaminated with some kind of aminopyralid.

Luckily the squash grew decently and I salvaged what I could of the potatoes.

In order to plan my garden in 2019, I need to know if the contamination is still present and which plants are affected and how significantly. The contamination eventually wears away but some sensitive plants will suffer for years.

To detemine the level of contamination, Washington State University recommends conducting a bioassay. The details of which can be found here. Basically you grow your plants in the wonky soil and compare against a neutral control to assess the effects on germination and for leaf curl.

Garden soil samples.

I am testing seven places in the garden against a control of my standard potting mix. I have planted beets, carrots, cucumber, and pea seeds in 6 pots of manure from 6 different garden locations, and have planted the same seeds in 4 pots of potting soil and vermicompost mix.

Brassica trial. (Control cells behind)

I’m running a concurrent test just for brassicas (cabbage, collards, kohlrabi, and tatsoi) to see if they’ll grow in a bed I would like to reserve just for them. Again these seeds will be measured against 2 control pots.

Awaiting results.

Right now they’re under my grow lights in the basement. As my mother says, “We shall see.”


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