Some physical qualities include soil density, permeability, porosity, temperature, thermal conductivity and heat capacity. These properties dictate how the biological micro organisms which feed on the plant organic matter survive. For example the penetration of heat, water and other essential organic residue depends on the density of the soil. Bio energy crops with their extensive and heavy root system have an essential role to play here. In addition to increasing the soil carbon content they can improve soil density and porosity. .
