subsoil ploughing
/ˈsʌbsɔɪl ˌplaʊɪŋ/(US subsoil plowing)
noun
Ploughing by means of a subsoil plough.
Origin
Mid 19th century; earliest use found in James Smith (1775–1839), writer and humorist. From subsoil + ploughing, after subsoil plough. Compare earlier subbing.