An update on the APLD’s soils guide

A few weeks ago I posted on the disappointing inclusion of compost tea in the APLD’s Guide to Sustainable Soils.  Included in my discussion of the issue was the suggestion that people involved in writing the guide also benefited financially from compost tea applications.  This led to some very honest and constructive emails between me and the APLD’s national leadership, which resulted in educating both parties.

Here’s what I found from the APLD’s President Susan Olinger and Sustainability Chair Toni Bailey:  As members of the Board of Directors of APLD, we can verify that there was no financial motive behind the inclusion of compost tea by the volunteers that wrote the soils guide.”  This is heartening and makes me feel less cynical about the motives behind including compost tea in the publication.

And here’s what I was able to impart to the leadership of APLD:  that while landscape designers may like to include compost tea as a soil amendment, the belief in its efficacy in improving soil tilth or biology is not supported by legitimate science.  It’s not a matter of sides, or opinions, but a matter of scientific evidence.

If the APLD doesn’t intend its guide to be a scientifically supported document, that’s certainly fine; landscape designers aren’t scientists, after all.  But since good soil science-based information is found throughout most of the guide, the inclusion of compost tea and mycorrhizal inoculants could easily be interpreted by others as science-based as well.

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Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - "The Garden Professors" Facebook group - Books:

One thought on “An update on the APLD’s soils guide”

  1. QUOTE:

    “the belief in its efficacy in improving soil tilth or biology is not supported by legitimate science. It’s not a matter of sides, or opinions, but a matter of scientific evidence.”

    I just had this discussion with an individual over at the UBC Botanical Gardens Forum. He is a very nice contributor, but he insists that the benefits of amending the soil in the planting hole was the only way he saved his Hazelnut Trees. He cited the fact that there were other Hazelnut trees that didn’t fare well at all where he didn’t amend, hence his comparison convinced him. But his observation didn’t include inoculating the trees with native soil backfills with a good mycorrhizal mix. He then later cited a study referenced in his Nut Association 2011 Report. It gave an example experiment of Oak Trees. It consisted of three comparisons.
    ‘One row was planted in native soil with no amendments, the second row was planted in amended soil using a commercial planting mix mixed with the native soil, the third row was planted by placing the potted plants directly into the soil with the trees still inside the pots.’

    “Conclusions: The trees planted in the native soils with no amendments fared the worst with growth that lagged the other two rows, and several mortalities. The row with amended soils suffered one mortality and had growth at almost 175% compared to the non amended soils. The row planted in the nursery containers had no mortalities, and had growth at 285% compared to the non amended soils.”

    To save time, my response was here;
    Re: Soil amendments

    I hope he takes my advice and inoculates and keeps accurates record notes and phot
    os, not only we it burn something important into his memory banks, But I’d also be cheering for his experiment. I have never not inoculated Oak trees since my first real experience at doing so as referenced in my blogs link here on my name link.

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