The meaning “cultivated field” for *ŝadaw- is a highly specific PC innovation with no precedent in other Semitic languages, where this concept is expressed, inter alia, by the reflexes of PS *ḥaḳl- (Fronzaroli 1969 :8‒9, 26)
PS
*ŝadaw- - open country, wild, uncultivated place
(Fronzaroli 1968: 269‒270, 287; Kogan 2011: 190; Kogan 2015: 307)
reconstruction with *-w (rather than -y) seems to be assured by well-attested spellings with -u-/-w- in Sargonic (śa-dú-e, śa-dú-im) and Old Assyrian (ša-ad-wi-im, ša-du-im), v. Kienast 1994:278‒280 and CAD Š₁ 51 respectively
Ugaritic
šd - open field, stretch of cultivated land; field, land, plot, estate, farm
(DUL 807)