In summer, we reported on our own tests with biochar on an agricultural area of our partner farm, the Högen Hof, for potato cultivation. In the process, 2 tonnes of biochar, which were provided to us by Circular Carbon, were applied to an area of half a hectare. For comparison, another half hectare was not treated. Already after a short time, clear differences were noticeable. In a random sample in autumn, we found that the area treated with biochar produced more tubers with a higher weight on average.

In order to explore the use of biochar for other purposes, we decided to use it right in front of our doorstep. Now that the Brüning Group’s new office building in Bremen has been built, the outdoor area is due to be planted, for which we are working with Schröder Baumschulen GmbH & Co. KG as supplier of trees and Rengstorf Garten- und Landschaftsbau GmbH & Co. KG. We now use biochar concentrate in the tree substrates for this purpose. We receive the concentrate from our partner Sonnenerde. It is mechanically mixed with the respective tree substrate and added to the planting pit. In areas with coarse gravel, the concentrate is washed down into the cavities by means of a strong water jet.

The structure of the planting pits is as follows:

2-3 cm gravel
  20 cm sand
  20 cm topsoil
100 cm tree substrate + biochar concentrate (proportion approx. 10 %)
  50 cm tree substrate + RADILOX + biochar concentrate (proportion approx. 10 %)

All tree pits have a depth of approx. 195 cm. The area of the tree pits is:

Tree 1          ca. 70 m²
Tree 2-5     ca. 80,4 m²
Tree 6-7     ca. 53 m²
Tree slice (without number) above ground 4 m² accessible (below ground 20.25 m² no longer accessible)
Tree 8-9      ca. 38 m²
Tree 10-12  ca. 38 m²

We expect many benefits from the use of biochar, such as the stimulation of root growth, which has a positive effect on the stability and nutrient uptake of the trees. In addition, the admixture of biochar is said to increase resistance to changing climatic conditions such as drought and wetness. The improved water-holding capacity of the soil through biochar can lead to significant cost savings, especially in dry summers, as less irrigation is required. In addition, the application of biochar is said to support better overall growth and a more lush crown, which in turn can provide an increased cooling effect in summer. Last but not least, the use of biochar in combination with an open tree pit (according to the so-called ”Stockholm method”) contributes to extending the life expectancy of urban trees, which can also reduce the costs of replacing urban trees in the long run.

Given the promising results of our tests so far at the Högen Hof and the positive effects on potato cultivation, we are eager to see how the application of biochar in our immediate environment will affect tree health. We are already looking forward to the development of the planting and the positive changes it will bring.