Our Soils

Healthy soils are the foundation of productive land and healthy environments. They support farming, forestry, and native vegetation, store and filter water, cycle nutrients, and help protect rivers, wetlands, and estuaries from sediment and contaminants.

Looking after soils improves land productivity, reduces erosion, increases resilience to drought and heavy rainfall, and supports better freshwater and coastal outcomes — from the mountains to the sea (ki uta ki tai).

Soils in Nelson

The soils of the Nelson–Richmond area are shaped by the region’s complex geology, landforms, and climate. Underlying rock types influence soil depth, texture, drainage, and fertility, which in turn affect how land can be used.

A geological map of the Nelson–Richmond area shows the distribution of:

river gravels and alluvial deposits on valley floors
weathered sedimentary and volcanic rock soils
steep hill‑country soils formed on fractured bedrock
ultramafic geology associated with the Mineral Belt

Download this map

Understanding the geological context helps identify areas that are more vulnerable to erosion, compaction, or nutrient loss, and supports better land‑use and management decisions.

To learn more about our soils, take a look at the Soils Map Viewer from Manaaki Whenua Landcare Research.

View: Geological Map of the Nelson Richmond Area

Soil Erosion

Soil erosion occurs naturally, often triggered by heavy rainfall, steep or unstable geology, and loss of vegetation. It can be accelerated by land‑use activities such as vegetation clearance, intensive stocking or cropping, forestry harvesting, earthworks, and the construction of tracks and roads that expose bare soil.

Erosion can have significant impacts, including loss of topsoil (reducing soil fertility and productive capacity), sediment entering waterways (degrading water quality and aquatic habitats), damage to streambanks, fencing, and infrastructure, increased flood risk from sediment build‑up in rivers, and reduced land stability for farming, forestry, and housing.

Erosion in the Nelson

The main forms of erosion in Nelson are:

Soil slips and surface erosion on hillslopes, often during high‑intensity rainfall or following prolonged wet periods
Streambank erosion, particularly where banks are unprotected or stock have access
Land‑use‑related disturbance, including exposed tracks, cultivated areas, earthworks, and recently harvested forest land

Much of the steeper land most prone to erosion is under indigenous or plantation forest, where woody vegetation provides important protection. However, surveys show that many streambanks in pastoral areas remain unfenced and vulnerable to erosion.

Assessing Erosion Risk

The Land Use Capability (LUC) classification is used to identify erosion risk and match land use with land capability. LUC mapping helps landowners understand soil limitations (such as erodibility, wetness, or shallow soils), appropriate land‑use options, and where soil conservation measures may be needed.

Erosion Susceptibility Classification

The Erosion Susceptibility Classification is a tool developed for the National Environmental Standards on Plantation Forestry (NES-PF) to assess the environmental risk for plantation forestry activities, reducing the potential for erosion.

The tool divides the New Zealand landscape into four erosion categories according to risk:

Green (low) and yellow (moderate)— land less likely to erode. Plantation forestry activities are permitted.
Orange (high risk) or red (very high risk)— land more likely to erode. Most forestry activities in the red zone will require resource consent. Some activities, such as earthworks require consent on orange-zoned land with steeper slopes.

Reducing Soil Erosion

Common actions to reduce erosion include:

maintaining vegetation cover on slopes
planting trees on erosion‑prone land and streambanks
fencing stock out of waterways and gullies
protecting wetlands and seeps
careful management of tracks, earthworks, and cultivated areas
retiring highly erosion‑prone or unproductive land

Nelson City Council supports erosion reduction through the Hill Country Erosion Fund, working with landowners to stabilise vulnerable areas and reduce sediment entering waterways.

See Hill Country Erosion and Healthy Streams for more detail and support.

*Soil surveyor identifying different soils*

Soil Mapping

Soil mapping (also known as soil surveys) identifies different soil types and records where they occur across the landscape. Soil maps and their supporting information describe soil characteristics such as depth, drainage, texture, and erosion risk, helping landowners and planners understand how land can be used and managed.

Historically, soil maps were produced by field surveys and published as printed reports. Today, much soil information is available digitally, including through national tools such as S‑map Online.

Soil Mapping in the Nelson Region

Soil information for the Nelson City region is based largely on historic surveys, including:

Soils and Agriculture of the Waimea County (1966), with mapping dating back to the 1920s
General Soil Survey of the South Island (1968)
The New Zealand Land Resource Inventory (NZLRI), compiled in 1977 and later revised

At a regional scale, NZLRI mapping provides the most widely available soil information for Nelson. However, this information is relatively broad and not intended for detailed, site‑specific land management decisions.

Table: Main features of the soils in the Nelson City region.

Landform	Geology	NZSC	Soil Series	Main features
Coastal sands	Sand dunes	Recent	Tahunanui	Sands; weakly developed soils with low fertility; land uses include forestry, pasture, housing and recreation.
Floodplains	Alluvium and terrace gravels derived from erosion of mixed sedimentary and volcanic rocks	Gley	Motukaraka	Silt loams formed from marine sediments; poorly drained with low fertility and high soluable salt content; drained areas are used for dairy.
		Gley	Richmond	Clay and silt loams formed from finer, poorly drained sedimentary alluvium; high organic matter, good fertility; mainly used for dairy.
		Recent	Waimea	Clay loams to gravelly loams; well drained with some imperfectly drained; from sedimentary alluvium; high fertility but low potassium; mainly used for horticulture.
	Alluvium and terrace gravels derived from erosion of sedimentary rocks	Recent	Ronga	Silt loams with gravelly subsoils; moderately well drained with some well drained; low to moderate fertility; mainly used for pastoral farming.
Terraces	Alluvium from slates and shales	Brown	Rai	Silt loams; well drained; moderate to low fertility; land uses include pastoral farming, cropping and plantation forestry.
Terraces	Alluvium and terrace gravels derived from erosion of mixed sedimentary and volcanic rocks	Brown	Ranzau	Gravelly silt loams; well drained; moderate fertility with low potassium; land uses include horticluture, pasture and houses.
Rolling and hilly	Sandstone gravels	Brown	Wakatu	Silt loams; well drained; low fertility; land uses include pastoral farming and cropping.
	Calcareous sandstone and shale	Brown	Wantwood	Silt loams; moderate to high fertility; land uses include pastoral farming and housing.
	Volcanic rocks (spilites, keratophytes and tuffs)	Melanic	Sunnybank	Silt loam hill soils; well drained; dark brown clay loam subsoils with moderate to high fertility but with low phosphorus; land uses include pastoral farming and cropping.
Rolling, hilly and Steeplands	Greywacke, argillite and sandstone	Brown	Pelorus	Silt loam hill and steepland soils; well drained; higher rainfall produces some podzolised soils; low fertility; pastoral farming is limited to the easier topography.
Steeplands	A complex mixture of volcanic rocks and altered sedimentary rocks	Brown	Atawhai	Silt loam steepland soils; well drained with some moderately well drained; low to moderate fertility; land use is mainly pastoral farming, with large areas of scrub.
	Dunite and serpentine		Dun	Sandy loam (over silt loam) steepland soils; well drained; shallow soils with very low fertility; land use is mainly native forest reserve with some plantation forestry.
	Greywacke, argillite and sandstone		Lee	Silt loam steepland soils; well drained; shallow soils with moderate fertility; land use is mainly scrub with some pastoral farming where gentler slopes allow.
			Patriarch	Silt loam steepland soils; well drained; very shallow soils with very low fertility; land use is native scrub and forest.
			Whangamoa	Silt loams steepland soils; well drained; shallow soils with moderate to low fertility; mainly reverted scrub, some pastoral farming and suitable for plantation forestry.
	Alluvium and colluvium gravels derived from sedimentary rocks		Rai	Silt loam steepland soils; well drained; higher rainfall produces some podzolised soils; low fertility; pastoral farming is mainly limited to the easier topography.
	Granodiorite and diorite	Melanic	Otu	Silt loam steepland soils; well drained; shallow soils with low to moderate fertility; land use is mainly scrub and forest, some plantation forestry and pastoral farming where gentler slopes allow.
	Marble and limestone	Melanic	Pikikiruna	Sandy loam steepland soils; moderately well drained; low to moderate fertility; mostly native forest with pastoral farming on easier topography.
	Greywacke, argillite and sandstone	Ultic	Ketu	Silt loam steepland soils; well drained; shallow soils with with moderate to low fertility; mainly used for plantation forestry and pastoral farming with some indigenous forest.

Soil Classification

Soils in New Zealand are grouped using the New Zealand Soil Classification, which organises soils into orders, groups, and sub‑groups based on their properties. There are 15 soil orders nationally, with five soil orders represented in the Nelson City region, encompassing around 19 soil series.

Soils are sometimes also referred to by regional soil series names (such as Waimea or Atawhai soils), which can provide more detailed local identification.

See here for more information on the history of soil classification.

Using Soil Maps Effectively

Regional soil maps are useful for:

understanding general soil patterns
identifying erosion or drainage risks
guiding land‑use planning

For effective soil management on farms, property‑scale soil mapping at a finer scale (approximately 1:5,000–1:10,000) provides more accurate and practical information.

Understanding soil type and capability supports better land‑use decisions, protects soil health, and reduces risks to waterways.

Soil Quality

Soil quality (often called soil health) describes how well a soil functions for its current use. Because soils differ in their physical, chemical, and biological properties, different soils are suited to different land uses.

Healthy soils support plant growth, store and filter water, cycle nutrients, and protect freshwater and downstream environments.

Why Soil Quality Is Important

Soils underpin Nelson’s primary industries — agriculture, horticulture, and forestry — and support biodiversity and freshwater health.

Pressures on soil quality can come from intensive land use, cultivation, compaction, reduced ground cover, and some nutrient or chemical inputs. Declining soil quality can reduce productivity, increase erosion, and affect water quality.

From a te ao Māori perspective, soils are part of whakapapa, connected to Papatūānuku and Hine‑ahu‑one. Through kaitiakitanga, caring for soils supports their mauri and ability to sustain people and ecosystems.

Key Soil Quality Characteristics

Soil quality is commonly assessed through a combination of physical, chemical, and biological properties, including:

nutrient status (such as fertility and Olsen P)
organic matter (carbon content)
soil biology, including earthworms and microorganisms
soil structure and compaction, affecting drainage and root growth

(No single test defines soil quality — these indicators are considered together.)

Table: Soil quality characteristics

Soil quality characteristic	Measure	What it tells us	Why it’s important
Fertility	Soil pH	Whether a soil is acid or alkaline.	Some plants and animals will only live in soils at a particular pH.
Fertility	Olsen P (plant-available phosphate)	How much phosphate is available for plant growth.	Phosphate (P) is an essential nutrient for plants and animals. Plants get their P from phosphates in soil. Most New Zealand soils are low in phosphates and extra phosphate needs to be added for agricultural use.
Humus (organic matter)	Total C (carbon)	Organic matter content.	Organic matter helps the soil store water and release it in a steady way. Organic matter also helps a soil store nutrient and form a crumbly structure suitable for plant roots.
Humus (organic matter)	Total N (nitrogen)	Organic N reserves in the soil.	Nitrogen (N) is an essential nutrient for plants and animals.Nearly all the N in soil is in organic form (see anaerobic mineralisable N).
Biological activity	Anaerobic Mineralisable N (ANM)	How much of the total N is available to plants through microbial activity.	Mineralisable N is related to the amount and quality of organic matter and biological activity in soil. Soil life breaks down the total N in organic matter and converts it into forms plants can use.
Physical condition	Bulk density	Whether a soil is firm and compacted or loose and friable.	Plant roots cannot grow through compacted soil. Compacted soils also become waterlogged quickly, starving roots of oxygen. If a soil is too loose, it dries out very quickly and may be easily eroded.
	Macropores	How many large pores there are in soil.	Large pores (0.03–0.3 mm diameter) are needed for air to reach roots and for water drainage. The larger pores are the first to be damaged by compaction.
	Aggregate stability	How resistant soil aggregates are to breaking.	A stable ’crumbly’ texture lets water quickly soak into soil, doesn’t dry out too quickly, and allows roots to spread easily. This measure is most useful for soils used for horticulture and cropping.

Soil Quality Monitoring & Trends

In New Zealand, soil quality monitoring focuses on seven core indicators, assessed across different land uses. Results show similar patterns nationally and in the upper South Island, including:

soil compaction on pastureland
high Olsen P on dairy land
low Olsen P on dry‑stock land
high Olsen P and low carbon on cropping and horticultural soils

Monitoring helps track long‑term trends and guide land management improvements.

Looking After Your Soil

Maintaining soil quality supports productivity, resilience, and environmental outcomes. While some changes take time, most soil quality issues can be improved through management, such as:

regular soil testing and nutrient budgeting
maintaining vegetation cover and organic matter
minimising compaction and cultivation
managing grazing pressure, especially in wet conditions

Tools such as Visual Soil Assessment (VSA) and nutrient budgeting models (e.g. OVERSEER®) can help landowners assess and manage soil condition.

Soil Trace Elements

Trace elements occur naturally in soils or can accumulate from land‑use activities. At elevated levels, they can affect soil organisms, productivity, food safety, and future land‑use options. Monitoring in the upper South Island shows trace element levels are generally within target ranges and consistent with national results.