Bartlett Experiment in Chicago using Biochar with Street Trees

Erin Rasmussen

Bartlett Tree Experts April, 2011

In Chicago, Bartlett Tree Experts are experimenting with applying biochar to benefit urban street trees. They have more detailed information in their company press release:

From the picture it appears that they are drilling holes and side-dressing about 60 existing trees in the Wicker Park/Bucktown community. The application started this year and the study will continue for the next two years.

All trees were aerated with the same number of holes – no matter the treatment.

100% biochar was applied. This was applied by itself, in combination with fertilizer and a fertilizer only treatment was also applied. Control trees only were aerated and immediately backfilled with the soil from the hole. Biochar was applied at a rate of 1/8 pound dry weight per square foot surface area.

from their site:

Why: A large portion of street trees planted do not survive; of those that do, the average lifespan is 10 years - considerably less than a tree growing in its natural conditions. Street trees growing in soil pits surrounded by pavement suffer from limited root space, soil compaction, limited water and drainage, poor soil structure and nutrients, and pavement de-icing salts.

If biochar were to improve the growing conditions of urban trees, enabling them to live longer, its use could save municipalities and property owners in tree-replacement costs and help preserve valuable urban tree canopy.

They have been conducting a larger experiment with urban soils that includes a plot test at the Morton Arboretum and experiments with blending biochar into the soil mix when planting trees.