The Collaborative International Dictionary of English v.0.48:

Manure \Ma*nure"\ (m[.a]*n[=u]r"), v. t. [imp. & p. p. Manured
   (m[.a]*n[=u]rd"); p. pr. & vb. n. Manuring.] [Contr, from
   OF. manuvrer, manovrer, to work with the hand, to cultivate
   by manual labor, F. man[oe]uvrer. See Manual, Ure,
   Opera, and cf. Inure.]
   1. To cultivate by manual labor; to till; hence, to develop
      by culture. [Obs.]
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            To whom we gave the strand for to manure. --Surrey.
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            Manure thyself then; to thyself be improved;
            And with vain, outward things be no more moved.
                                                  --Donne.
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   2. To apply manure to; to enrich, as land, by the application
      of a fertilizing substance.
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            The blood of English shall manure the ground.
                                                  --Shak.
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