The Collaborative International Dictionary of English v.0.48:

Unproductive \Unproductive\
   See productive.

WordNet (r) 3.0 (2006):

unproductive
    adj 1: not producing or capable of producing; "elimination of
           high-cost or unproductive industries" [ant: productive]
    2: not producing desired results; "the talks between labor and
       management were unproductive"

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "unproductive":
   abortive, acarpous, arid, barren, bootless, celibate, childless,
   desert, desolate, drained, dried-up, dry, exhausted, fallow,
   fruitless, gainless, gaunt, gelded, impotent, ineffective,
   ineffectual, infecund, infertile, issueless, jejune, leached,
   menopausal, nonfertile, nonproducing, nonproductive, nonprolific,
   nonremunerative, otiose, profitless, rewardless, sine prole,
   sterile, sucked dry, teemless, unavailable, unavailing,
   uncultivated, unfertile, unfruitful, unplowed, unprofitable,
   unprolific, unremunerative, unrewarding, unsown, untilled, useless,
   vain, virgin, waste, wasted, without issue