NCSU Vermiculture Conference topic – Evaluating Compost Extract Applications: Reflections from Laguna Blanca, Argentina

Speaker: Eric Carr, Rodale Institute. To start he thanked people from Laguna Blanca, Rodale Institute, and his family. In this presentation he will talk about evaluating compost materials on a large scale.

Here are my notes:

At the beginning of his talk he mentions the goal of process of putting organic materials in water: to extract from a solid and use it differently. He prefers term “extract” to “tea” terminology.

He emphasized the importance of producers doing our own tests on our own products — a benefit is to improve the marketability of the product. Since results of different products are highly variable, widespread adoption of compost application on crops isn’t happening.

At what scale is use of organic soil amendments financially beneficial? On a small scale — yard, hoophouses, yes it is often financially beneficial, but what about when you get into hundreds of acres? This was explored in his project.

Laguna Blanca, Argentina project — they are starting with clay soil but the goal is sustainable organic agriculture. A beautiful aerial shot of the farmland was shown.

Composting he worked with: windrow, vermicompost, liquid extracts, and application on crops.

    Tractor was used for windrows of dairy manure and vegetation. They also have a windrow turner.
    Vermiculture in roof-covered cement beds, harvesting was a challenge — it was done with a tractor. Hand feeding and watering every 3 days.
    Extracts made in large brewers — he designed a simple barrel that didn’t leak. He circulated material but didn’t aerate it. Extract was filtered so it didn’t clog sprayer.

His testing — looking for plant growth:

    Germination test on a small scale first. Data shown on 20% vermicompost to water extract. the only increase for lettuce grown in vermicompost was in shoot length.

    Greenhouse and small plot trials — inconclusive and difficult in this setting since irrigation was limited

    Field trials: On soybean and sorghum using 20% worm compost extract applied by tractor with a sprayer. They did a water control for comparison.

    Soybean trial: Well-diluted extract did not significantly improve growth. Vermicompost was extracted for 10 days then stored for 10 days.

    Sorghum trial: Aerated extract more for this trial and didn’t dilute it as much. Still not much difference in growth in first trial, but in second trial where a second dose was applied, there was a significant difference. One note, plain water might have had the same result as there was no water control in this experiment. Other things that could be evaluated if a trial like this was done again would be the timing of the collection of data.

He concluded by saying that in evaluating a process that a cost benefit analysis would show if you are maximizing your benefits by using a vermicompost extract in your crop production — everyone’s variables are different so results of the processes will vary.

The reference text sold at the conference, Vermiculture Technology: Earthworms, Organic Wastes, and Environmental Management, is available on in hardcover and for Kindle.

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