The Collaborative International Dictionary of English v.0.48:

Conacre \Con*a"cre\, v. t.
   To underlet a portion of, for a single crop; -- said of a
   farm. [Ireland]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Conacre \Con*a"cre\, n.
   A system of letting a portion of a farm for a single crop.
   [Ireland] Also used adjectively; as, the conacre system or
   principle. --Mozley & W.
   [1913 Webster]