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Biochar decreases leaching by up to 62%

Biochar decreases leaching by up to 62%

Plants thrive off nutrient rich soils, and if the nutrients get washed away by rain, your plants will not thrive.

Further, nutrient leaching is a major environmental concern, as much of the nutrients from the fertilizers we put in our lawns and gardens (even organic ones like compost) end up washed away into our lakes and rivers. This causes abnormally high nutrient concentrations in water ecosystems leading to algae blooms and other knock-on effects.

An algae bloom in Lake St. Clair in July 2015. The lake is bordered by Detroit, Michigan to the west and Canadian farmland to the east. NASA/NOAA

One of the most important environmental benefits of biochar (other than sequestering CO₂) is that is helps soil hold onto nutrients. This has the doubly positive effect as it allows your plants to access these nutrients leading to higher growth rates, and also keeps run-off nutrients from affecting the environment.

There have been a number of peer reviewed studies published on biochar's ability to reduce nutrient and mineral leaching, but we teamed up with Jonathan Montgomery Ph.D., from Humboldt State University to test it out for ourselves using our very own biochar.

To do this, we planned a simple experiment. We...

  1. Packed soil into pots at various amounts (from 0% to 15%)
  2. Added 200 mL concentrated nutrient solution to each of the pots (we used Miracle Grow). 
  3. Poured 750 mL of distilled water through the pots.
  4. Collected the water and assay for nutrient concentrations.

We used the same sandy and loamy solid we used in the Soil Drydown Study which we obtained from Humbolt, California.

For the minerals, we tested for Calcium (Ca), Magnesium (Mg) and Iron (Fe) because they behave like most nutrients in soil due to their charge and size (being bivalent cations). We did not directly measure for phosphorus and nitrogen in this study, because the assaying process was labor prohibitive, but we hope to do this in a future study.

All that said, we completed the study on September 27th, 2022 date and here were the results:

Nutrients leached based on percentage of biochar in soil

The raw data is available here.

We found is especially interesting that:

  • Biochar application reduced the leaching of all the minerals that we tested in the study (Ca, Mg, Fn). 
  • Most pronounced in Calcium, where our 10% biochar concentration decreased leaching by 62%
  • Majority of mineral retention benefits seem to be realized at 5% biochar

The limitation of our study are that:

  • We only ran the test only once. (we need to reproduce it one more time to publish results)
  • We did not test with Nitrogen and Phosphorous for now as mentioned above
  • We only tested on one type of soil.

Although the data did have its inconsistencies, such as Iron results being inconsistent, it is clear that biochar had a strong nutrient retention effect. We were happy to verify this ourselves using the biochar used in our products.

Note that in this study we used unactivated (naked) biochar for simplicity, the nutrient retention rate of the activated biochar we used in our products will be even greater than what we measured here. (See this study as to why).

You can buy the exact same biochar we used, made from sustainable forestry waste in Canada, by following the link below.