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First look at Midwest Labs results. Bonus: DNA extraction update

Updated: Dec 7, 2020

Updates:

  • First, I hope everyone had a great Thanksgiving. Personally, things have been a bit nuts around here, but I am happy to have time around the holidays to give you a first look at some of the data.

  • We have concluded all of the testing of the samples sent to Midwest Labs for their compost plus package. We had a total of 19 vermicompost samples that were tested in triplicate.

  • All of the samples submitted for sequencing analysis have had their DNA extracted! We had some equipment failure issues, but I think it all turned out OK. I was hoping to have a separate post with pictures of the process; unfortunately there was no photography allowed, and I can't even properly thank the people who deserve it.


DNA Extraction: Sample loading

I did allow pictures in my own basement though, where we weighed and loaded all 220 samples. This was my first time using a high thought-put kit where the extraction process takes place in a series of 96 well plates (top right). It was tricky to avoid cross contamination between wells so we used a transparent sheet with a small hole cut out. This is probably the single most time consuming step of the process. Everything else is done 8 wells at a time with a multichannel pipette.


Physical Vermicompost Properties

Moisture, pH, and conductivity mad sense to talk about together and of the results showed some of the biggest differences between vermicomposts. I am no compost expert so please chime in if anything jumps out of you.



Overall, I am really pleased with the small error bars (1 standard deviation). It generally means everything went well in terms of sampling and testing. As a producer, I would feel confident only having single test done and getting accurate results. Moisture values look pretty consistent while conductivity and pH have a higher range of values. Some of the higher conductivity might be worrisome, but from what I've seen all the values look pretty normal. I still need to input data from the questionnaires to start making sense why some of these values are higher or lower.


Nutrients and Metals

I selected the most interesting nutrient and metal profiles. I imagine most of these values are pretty standard for vermicompost. I did not include the nitrogen species because there was not much nitrogen of any type in any of the samples. I also neglected showing a bunch of the heavy metals for the same reason although there were a few outliers.


Organic carbon ranges seem low to me, but remember to double the value to get % organic matter. On average, samples have about 10% organic carbon or 20% organic matter. I would have guessed higher.


Phosphorous and potash track well together, which makes sense since potash is likely to be the main source of phosphorous.


I'll let you look through the rest of the metals but I'm glad to see some variation between producers. The variation is good because if everyone's vermicompost was about the same the it wouldn't be very helpful in determining what affects the microbial communities. Based on this initial data I would hypothesize that that the microbial communities will be quite different based on taxonomic identification (who is there).


Ultimately, we will mesh this data, the questionnaire data, and sequencing data to try and understand which factors seems to play the largest role in shaping the microbial community. Everything will be reprocessed and polished, but I wanted to give you all a first look. I am hopeful to still generate the sequencing data by the end of the year, but there are still a few variable at play.


Again, if you spot something unusual please let me know! I am no expert in with this type of data. I would like to find any potential issues before we get too far into it! Also, if you are a vermicompost producer who would like their Midwest Lab results now; I am happy to send it to you. Please just shoot me an email! Everyone will eventually get individual results of all data once the analysis is complete.

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4 Comments


Zack Jones
Zack Jones
Dec 03, 2020

This was my biggest concern as well and perhaps why vermicompost is not recommended to be used as 100% soil for plants and recommend to be added at maybe 30%? Anecdotally, I use my vermicompost blended with ~30% pearlite without issues for houseplants. I did not add my own vermicompost to the analysis though since I don't have much of a reproducible process, however it contains no manure. I would guess (again I'll look into this for sure soon) that perhaps the difference in salts is due to animal waste? For small applications, I don't think it'll be an issue but the application of human "biosolids" or treated municipal waste from water treatment has become a bit of a proble…

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Dan Lonowski
Dan Lonowski
Dec 03, 2020

Speaking of conductivity, the range from Midwest Labs for "Desirable range for most plants" is 0.6 - 3 mS/cm. If so, then more than half of our sample results are outside (above) that range. I thought that a desirable range would extend up to a max of 5.0. But even with that, 6 of our samples would be above the range. Looks like we collectively may have issues with soluble salts?

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Zack Jones
Zack Jones
Nov 30, 2020

Hi Dan,


I also found the range of pH interesting in that there isn't really a majority of samples either above or below 7. The questionnaires will hopefully shed some light on this. My main experience with bigger animals is fish. Like worms, they be can sensitive, and have usually have recommended pH ranges . In most cases the experts say stability out weighs a specific pH range and perhaps the same is true of worms.


For conductivity, I neglected to show the sodium/chloride data. By eye, it somewhat correlates to conductivity but I think there are larger factors or other salts perhaps. I would calcium is not tracking with cond. because the source is likely egg shells and not…


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Dan Lonowski
Dan Lonowski
Nov 29, 2020

Hi Zack, this is starting to come together nicely! The range of pH caught my eye - I had some clients with low pH around 4-5 and I'm surprised the worms were comfortable in that. But they made some really nice vermicompost! Also I'll be interested to see if we can find data correlating with the highs and lows of Conductivity. Just looking for patterns, I see phosphorus and potash tracking CEC well, but not calcium. Another one is the sample with high S but no P or K - wonder what their feedstock was and their process! Also, I wonder about the variability on sample 5's P & K. Maybe an outlier in the data, and you could lo…

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