Related Rule
New Zealand
Practice Relating to Rule 54. Attacks against Objects Indispensable to the Survival of the Civilian Population
Section C. Attacks in case of military necessity
New Zealand’s Military Manual (1992) states:
In recognition of the vital requirements of any Party to the conflict in the defence of its national territory against invasion, derogation from the prohibitions contained in paragraph 2 [prohibition to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population] may be made by a Party to the conflict within such territory under its own control where required by imperative military necessity.
As a result of this provision, Parties may no longer embark on a scorched earth policy with the intention of starving civilians, even in their national territory, unless that part of the territory is under their control at the time of devastation: scorched earth is no longer available as an offensive policy. It is still permissible to destroy objects indispensable to the survival of the civilian population in the course of ordinary operations if it is militarily necessary for other reasons, for example, to destroy a wheat field to deny concealment to enemy forces. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 504(5), including footnote 10.