World’s Soil Resources

In New Zealand, deterioration of soil physical condition is common in grazed pastoral systems due to
animal treading. Sparling and Schipper (2004) in their survey on the condition of soils in New Zealand reported
moderate compaction on a large proportion of pasture soils and that about half the sites under dairying were
below the critical threshold of 10 percent air-filled porosity. Mixed cropping soils also had low macroporosity.
Drewry (2006) indicated that the physical condition of the top 10-15 cm naturally recovers when animals are
partially or completely excluded from pasture and proposed the integration of a recovery cycle when managing
grazing systems.
15.5.8 | Sealing and capping
Most towns and cities in the region were established during the 19th century and they were nearly all built
on, or adjacent to, land highly suited to horticulture and cropping. The encroachment of urban and peri-urban
development has seen the capping of this land. For economic reasons, it is highly unlikely that these good
quality soils will ever regain their biological function. The loss of these strategically important soils is occurring
throughout the region and is particularly significant in Fiji, some of the small Pacific islands, New Zealand and
Australia. Population projections (Table 15.2) indicate that the problem will intensify in coming decades. The
rate of sealing and capping is not being monitored at present.
15.6 | Case studies
15.6.1 | Case study one: Intensification of land use in New Zealand
Significant changes in land use have occurred across New Zealand in recent decades. The impacts of
these changes on soil resources are reasonably well understood because of a substantial commitment to
fundamental and applied soil research within the country. This effort is integral to the current and future
international success of New Zealand’s agriculture sector.
An important development in the evolution of land use in New Zealand that contributed to intensification
was the removal of all agricultural subsidies in the mid-1980s (MacLeod and Moller, 2006). New Zealand
is unique because it is the only developed country to be largely exposed to international markets. As a
consequence, current land management decisions are now driven directly by the response of land managers
to market prices for agricultural products.
The removal of subsidies triggered a decline in traditional sheep farming. Sheep numbers dropped from
around 69 million in 1980 to 39 million by 2002 and 31 million in 2012. Plantation forests were established on
former sheep pastures and forestry expanded from 0.85 million ha in 1980 to 1.8 million ha in 2000, with 95
percent under private ownership. The strong international demand for dairy products caused an increase in
the number of dairy farms. Dairy cattle increased from around 3.0 million in 1980 to 5.3 million by 2002 and
6.4 million by 2012. Cattle stocking rates and productivity also increased (Ministry of Agriculture, Fisheries
and Food, and Statistics New Zealand). Some of the pastures converted to plantation forests in the 1980s and
1990s are now being converted to dairy pastures following the harvesting of mature trees, and even partly
grown trees have been removed and replaced by pasture for dairy farming (Sparling et al., 2014). Horticulture
has also expanded. The area of horticultural crops has increased by 40 percent in just over 10 years (HortNZ,
2014).
Most of the intensification of agriculture in New Zealand has occurred on the better class lands. There
has also been the expansion of dairy farming onto soils that have previously been less intensively farmed,
such as artificially drained Luvisols in the Southland region and irrigated stony Fluvisols and Leptosols of the
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in the Southwest Pacific