This is one solution that we used to use at the Organization of American States. 16,400 references. Presumably they "do" something on these vast landholdings - i.e. ranching.

Note that "rancher" can imply huge landholdings - look at the King Ranch in Texas (825,000 acres, 24,000 km2). Unfortunately, "large rancher" refers to a large ranch-style home.

Examples of "large landholder":

LARGE LANDHOLDER DEAD.; Earl Howe Had 33700 Acres -- An Ancestor ...
LONDON, Sept. 26.-Earl Howe (Richard William Penn Curzon-Howe) is dead. He was the third Earl, and had been Lord Lieutenant of Leicestershire since 1888. ...
query.nytimes.com/gst/abstract.html?res=FB0B12FD3C5B11738DDDAE0A94D1405B808C

Nov 2, 2007 ... In 1784 George Washington, famous Indian fighter, large landholder and slave owner, advised the Continental Congress that it would be ...
fusilier.wordpress.com/2007/11/02/washington-indian-fighter-large-landholder-slave-owner/ -

Large landholder moves to protect development rights. By DINAH VOYLES PULVER Environment Writer. It's the 57000-acre question: What does the future hold for ...
www.news-journalonline.com/special/miamicorp/newEAST0110080...

involved in activities to denounce the large-landholder system and in favour of agrarian reform. In honour of the 19 landless people ...
www.landaction.org/display.php?article=77

A large-landholder model was promoted by modernising large landowners. A medium- landholder model was advanced by promoters of European immigration and urban ...
journals.cambridge.org/abstract_S0022216X98005082

THE LARGE LANDHOLDER PATRON SUPPLIED A PROTECTED, SELF-SUFFICIENT VILLAGE, SUPPORTED THE CHURCH, AND PROVIDED THE NECESSITIES OF LIFE FOR HIS PEONS. ...
eric.ed.gov/ERICWebPortal/recordDetail?accno=ED013150