Our Backyard Soil Sample – The Results Are In!

Four years ago Now

A few weeks ago we had our amazing interns prepare a soil sample to be sent off to the Soil Food Web Lab in Vulcan, Alberta. (See the blog, Testing Our Soil for a Nutrient Dense Garden). A few quick weeks later, our analysis came back, and we were told by the lab that our “sample’s biology numbers were one of the best we have seen for garden samples”.

We’ve been telling people for years now that compost is the most effective way to improve soil texture, nutrient density, tilth, carbon content and overall health, and now the results are in.

When we started our garden almost four years ago, growing anything in our backyard seemed hopeless. You can see (top right) what our soil looked like when we started. It was basically chunks of sand and clay with the consistency of concrete. Not a very welcoming home for new seeds.

So right from the beginning we started mulching, using cover crops and adding compost — which have all helped hugely. The most significant change occurred this year, however, when I unknowingly did a compost experiment over the winter. A few years ago Annette, my mother in law, bought a Nature Mill Composter for her kitchen. I have to admit I was a little skeptical of a machine that uses electricity to produce compost when most compost piles do it for free! But this little unit pumps out 8 litres of compost every week, which I dumped onto my potato bed throughout the winter. Last week when I was preparing the bed for planting, I couldn’t find any of the large concrete clay sand chunks from previous years, and the soil was completely friable! Amazing!

The continual compost additions throughout the winter made a huge difference despite the fact that it was frozen. This was not something I anticipated. But now that I know, I’m going to continue these treatments throughout the year to bring the quality of the soil up in the rest of the beds.

Below are links to our lab results (PDFs), for those who want to see what a Soil Food Web Analysis looks like. (All the microbiology buffs reading this will probably notice that the our ciliate count is quite high, which is not good as it indicates anaerobic activity in the soil. This makes complete sense to me, as parts of the garden are still super compacted, lacking organic matter, and need additional amendment with compost and compost tea.)

• Soil Chemistry Report
• Soil Report Interpretation
• Final Soil Report

To get a better understanding of our results, we asked Doug Weatherbee, Soil Food Web Advisor and guest instructor for our upcoming soil course, to weigh in on the report and tell us what is good, bad, and how can we improve it.

Looking really good Michelle and Rob! Congratulations on your work bringing this soil back to life. You have fantastic total fungal numbers in relation to total bacteria for a garden. You could add some fungal foods (humic acids, fish hydrolysate, kelp) to bump up the active fungi and benefit from all the fungi you have present in the soil (your great total fungi #s). Also, your fungi hyphal diameter is large indicating, generally, that you have plant disease suppressive fungi in your soil. Fantastic. If you find that your brassicas aren’t doing as well as others in your garden, you might want to beat up the soil (till) where you plant the brassicas in order to make it a tad bit more bacterial dominated (brassicas tend to thrive more in slightly bacterial dominated soils). In terms of your high ciliate numbers, if you reduce your tillage or soil-turning as much as possible, and you leave non-diseased plant residues/roots you’ll see an increase in the soil biology you already have, and they in turn will increase soil carbon content and aggregation. The results will be an increase in aerobic nooks and crannies in your soil and a slight drop in the habitat for ciliates, thereby dropping their numbers and hopefully increasing the habitat for predatory nematodes (they’ll keep any plant root feeding nematodes in check and increase nutrient cycling for your plants). Overall, great work. — Doug Weatherbee

This summer we’re looking forward to getting a compost tea brewer to get our soils functioning at peak capacity. We can’t wait to do another soil sample next spring to see how everything changes throughout the upcoming year. Stay tuned!