Studies have proven that as the plants
grow older, roots tend to accumulate and increase (from 59
up to 73%) mostly on the topsoil surface at a depth from 0 to
15 cm and slightly decrease (from 35 down to 20%) at lower
levels at 16e30 cm depth, while root biomass at 31e45 cm
depth stay fairly stable (from 7 up to only 8%) [29]