The NPS seeks to control the unplanned encroachment, particularly of lifestyle blocks, which today's consultation document says can carve up highly productive land into inefficient parcels. It will require local government to plan for suburban expansion to try and preserve so-called 'elite soils'.
Urban Development Minister Phil Twyford is due to launch a further NPS creating national requirements for the growth of New Zealand's cities and in Auckland, in particular, where house prices are among the highest in the developed world as a proportion of average household income.
The focus for the immediate future is on the South Auckland-to-Hamilton 'corridor', where the government is seeking to develop better rail and other public transport options while preserving the area's food-basket status.
That NPS was part of stopping "house prices going crazy", said Parker.
"We need to house our people and to feed them too."
O'Connor said highly productive land, often found near existing towns and cities, had become taken for granted and been lost to food production in recent years.
"We cannot afford to lose our most highly productive land. It brings significant economic benefits including employment for nearby communities, and adds significant value to New Zealand's primary sector," he said.
Parker said councils had approached the issue on too much of an ad-hoc basis and "the pressure for urban growth has over-run the capacity to maintain our productive base."
Asked whether it was fair to deprive the owners of market gardening land the chance to sell for subdivisions at higher prices than the land is worth for horticulture, Parker said all private land is subject to zoning and other restrictions on its use.
"The horticulture sector wants these changes," he said.
Once decisions are reached, councils will have five years to identify and then organise protection for areas with elite soils. Both ministers conceded there is nothing to stop existing landowners selling for subdivision or lifestyle blocks, except to the extent that those areas were already covered by documents such as the Auckland Unitary Plan.
The new process will use a decades-old land use category database, which the draft acknowledges is not detailed enough for pinpoint identification of elite soils or to undertake the detailed spatial planning that modern resource management regulation will increasingly require.
Submissions on the draft NPS are open until October 10.