biomass at the 20-30 cm soil depth. Absence of speargrass rhizomes at soil
depths greater than 30 cm could be due to speargrass ecotype, soil physical
structure, chemical status of the soil or a combination of these factors.
Although Horowitz [1972] found that johnsongrass rhizomes could survive at
45 cm soil depth, rhizomes were similarly concentrated in the upper 15 cm
of the soil.