Toxic Elements in Soils

MAMMALS and birds sometimes seek shelter or nesting sites in the ground. Many of them scarcely affect the soil as a medium for plant growth. A notable exception is the soil-dwelling rodents. Although their acreweight is usually only about a few pounds even in the uncultivated land, their soil transporting activities sometimes are considerable. In building their tunnels and nests, they transport large quantities of subsoil to the surface. The open burrows in turn catch dry or waterborne surface debris and humus-rich surface soil. Water movement into the subsoil may be facilitated by the presence of rodent burrows. In some circumstances this is desirable; in others it is not. The farmer applying irrigation water does not always express himself in temperate language when he finds gopher holes.