Calculating the required soil volume per tree is not straightforward. Several parameters are needed to quantify the soil volume. Of course, there are several rules of thumb that are often used to calculate the minimum required soil volume per tree. 0.5 to 1 m3 per m2 of tree crown projection area. But these rules of thumb are very general. And say nothing about the quality of the volume indicated. Scientific research shows that 1 m3 of loamy soil gives the same tree growth as a staggering 5 m3 of structural soil.