Soil sampling device with frangible section and method of sampling

A soil sampling device for collecting samples of soil provides a single use unit with an integrally molded plunger. The soil sampling includes a cylindrical body having first and second ends, with the body comprising a cylindrical wall having a longitudinal axis and an end wall. The cylindrical wall extends between the first and second ends of the body, with the end wall being positioned at the first end of the body. The second end of the body defines a mouth which is adapted for inserting into soil. A piston is positioned in the body, and the end wall includes a projecting member extending outwardly from the body which defines a plunger. The end wall includes reduced cross-section around the projecting member and is adapted to break when a force is applied to the projecting member to thereby permit the plunger enter into the body and thereby push the piston along the longitudinal axis to expel a sample of soil collected in the body. Preferably, the piston is frictionally held in the body, for example by frictionally engaging an inner surface of the cylindrical wall. Optionally, the piston includes at least one seal for frictionally engaging the inner surface of the cylindrical wall.