Friday, April 30, 2010

Herbicide Carryover: Bioassay Results

About a month ago I reported on a farmer who had received manure that was contaminated with the herbicide picloram and applied it to his vegetable production fields. We conducted a bioassay on the contaminated land to see if the soil was safe to plant. Last week we assessed the results of the test.

The first site we tested was "Moses". This field had been contaminated by the manure, however the manure was only applied in a small amount in each of the holes where tomatoes were planted. From the test, it looks like this site should be safe for planting this year.
Side note - The greenhouse where the seedlings were located was very hot, so some of the "crispy" edges are more than likely due to the temperature because some of the control plants also were affected.

Beans are sprouting in soil that was contaminated with manure containing the herbicide picloram.

Control test using soil that was not contaminated.

Next up was the field we called "Fred". Manure was applied to this entire field. The field appears to be unsuitable for vegetable production at this time. The grower will not be producing on this plot this season.

Bean seedlings did not emerge from the soil collected from field "Fred".

Control soil taken from part of field where no manure was applied. Seedlings look pretty good.

We were also concerned about the field below "Fred". There were a few spots where the grower's Austrian winter peas did not emerge. So we tested these areas to see if runoff from "Fred" was the reason. Looks like that field should be okay.

Bean bioassay of soil taken from a field below "Fred" where some water runoff from "Fred" flows.

The final plot that was tested was a field that is located next to the growers house. This field had the most manure applied and there was no soil available to test as a control. As you can see, this soil appears to be unsuitable for vegetable production.

No bean seedling emerged from the soil taken at the home site. This plot had the most manure applied to it.


Overall, we were not surprised by the results. All of our seedlings from the control plots emerged successfully. The seedlings planted in soil from the field with the least amount of manure applied ("Moses") emerged and there appeared to be no damage. The grower is planning on producing vegetables in this field this season. Luckily, the grower did not lease field "Fred" this season due to other reasons.

The most unfortunate situation is the field that is located next to the house. The grower will continue to work this land to allow for the elements, sun, rain, etc to break down the herbicide. He is considering growing a less susceptible crop in this field, such as corn or a grass cover crop.

To read more about the bioassay and herbicides that may be a problem in manure, read Dr. Jeanine Davis's article "Herbicide Carryover in Hay, Manure, Compost and Grass Clippings".

**UPDATE May 2010**
New Herbicide Carryover publication available!

3 comments:

Jeanine Davis said...

Sue, thanks to you and your farmer for sharing this story and the great pictures! There are not many pictures to demonstrate the bioassay. Now we have them. Do you mind if I use these in some of my presentations? I will give you full credit, of course, for doing the work AND taking the pictures. Good job.

jakesfarm said...

We made a decision long ago to never use manure on our farm. Now we see one more reason besides potentials of food borne illness. Our practice is to grow 'green manure' cover crops and turn them under. I never buy compost either. I have read some negative things about our favorite fertilizer...nature safe. I wonder what they are hiding?

Ben said...

As a potential new farmer self transplanted to WNC to try and get some actual experience in agriculture, trying to gleen some inside knowledge on soil quality, soil suppliers, and proper local remediation processes through online sources is a daunting task. Thank you for posting this research in an easy to read and easy to obtain format. The work you are doing (which I am sure takes a long time to procure results) is imperative to newbies like myself that are trying to figure out the ground steps to achieving sustainable farms. having just a few books from bill mollison, no background in agriculture, and little time to actually implement the steps needed to get even a sizable garden started, it is readily available local information like this that eases the transition from someone who only consumes to someone that produces more than they consume. please feel free to blast my email with any links dealing with good soil providers in WNC, info on local soil test results, and quick access info on remediation processes to deal with faulty earth. then lets pray that whoever keeps pumping aluminum chem trails into our atmosphere and spraying pesticides onto cattle feed plots and fields is stopped.
oambiento@yahoo.com