Glossary

Soil characteristic terms

Soil Characteristic	Metric Description	Use Relevance	Effects on growing conditions and commercial production
Rooting depth	Depth to the first layer that obstructs root growth	Screening	Plants require sufficiently deep soil that allows for proper root development and exploration of soil resources. Limited rooting depth reduces the availability of water and nutrients causing loss of production and may also impact physical support for larger trees.
Plant Available Water (PAW)	Soil potential plant available water down to a depth of 90cm	Screening	Large soil potential plant available water provides resilience to drought through greater storage capacity and may enhance the availability of other resources. Limited storage capacity can lead to water stress over the summer and have a negative impact on production. All soils can soak up and hold onto different amounts of water. Sandy soils hold less water than silt soils that in turn hold less water than clay-rich soils. Clay-rich soils hold water too tightly for plants like grasses to access easily. Deep, stoneless sandy loam soils, clay loam soils and silt loam soils have high amounts plant available soil moisture. (Stones take up space in the soil but don't hold water, unless they are pumice stones that have holes them).
Soil Drainage Class	Dominant drainage class ranging from 1 - Very poor, 2 - poor, 3 - imperfectly drained, 4 - moderately well drained, 5 well drained and 6 excessively drained-	Screening	Well drained have good aeration which is essential for good root development and function. poor drainage leads to waterlogging, oxygen deprivation, and increased susceptibility of diseases, these reduce production and may lead to plant death. Excessively drained soils may be drought prone.
Soil pH	Soil pH over the top 15cm	Screening	Soil pH affects the availability of nutrient and also is linked to toxicity. Extreme soil pH levels (either acidic or alkaline) can adversely affect nutrient availability, affecting plant growth and development. Soils need to have a pH of around 5.8 to 6.2 for optimal pasture growth. If soils have a pH of less than 4.5 they will often toxic levels of Aluminium which causes issues similar to drought, because plant roots keep dying off. If the pH is greater than 8.5 the trace elements get out of balance.
Stone content of surface	Volumetric content of gravels (particles > 2 mm) over the top 20 cm	Screening	A large stone content may indicate reduced plant available water and/or impediment to root penetration. Excess of stones in the surface may hinder soil cultivation and/or harvest of some crops (e.g. potatoes)
Soil Texture	Dominant texture class in the top 60cm of the soil.	Post-screening	Soil texture may be linked to several aspects that affect crop growth and management. It can indicate water-holding capacity, nutrient retention, how easy it is to work the soil, root penetration, and the potential for waterlogging.
Phosphate Retention or Anion Storage Capacity		Post-screening	Phosphate Retention or Anion Storage Capacity is an important feature of some soils especially Allophanic Soils containing volcanic ash. These soils are yellow-brown in colour and friable (crumbly, and light-weight). They may feel greasy or extra slippery on tracks when moist. These soils have a very high Phosphate Retention or Anion Storage Capacity which means they need a lot more phosphorus fertilizer before they produce well than other soils like Pumice soils, Brown Soils, Recent Soils, Ultic Soils or Pallic Soils. Although this can be very expensive, these soils are very resistant to pugging, can be cropped earlier and later in the season than other soils and hold moisture longer than other soils.
Salinity		Post-screening	Salinity is often considered in land evaluation rulesets internationally. In Aotearoa, the vast majority of soils do not have a salinity imbalance. Such soils need a lot of lime and irrigation water and salt tolerant plants to overcome the salt levels present. Where salt levels are very high it can be very important to not remove vegetation because you can risk causing salt lakes to form, but this is not normally a problem in Aotearoa. However there are a few areas of the country where saline soils exist. These are easiest to describe here. These areas include small areas in unirrigated parts of Central Otago and the MacKenzie Country where there are "Semi-Arid Soils" mapped in S-map or in the Fundamental Soil Layer. Semi-Arid Soils are more similar to the soils found in drier continental locations such as Australia, USA, Turkey and Iran where salt lakes are present due to high evaporation and low rainfall leading to salts not being washed out of the soil profile like they are in the rest of Aotearoa. There is also a different sort of saline soil here in Aotearoa associated with low-lying land near the ocean. Look for old uplifted lagoons like Whakaki near Wairoa and Ahuriri near Napier. There is also whenua that is low-lying around Waitematata Harbour from when the world's sea level was 6m higher than it is today. Some of this may still be saline. Look on S-map Online for the "Ahuriri" family, or for "Saline Recent Gley" or "Saline Orthic Gley Soils".

Soil drainage terms

The length of time which water sits in the large pores in different types of soil for, or in different landscapes for, after wet periods. The length of time the water sits in the soil profile dictates to what extent oxygen is prevented from being available to the chemicals and organisms in the soil (ie how long soils have to hold their breath). The more the soils have to "hold their breath" during a year each year, the more they get grey, green, or eventually even purple. This process is gleying, when iron is leaching out of the soil in oxygen deprived conditions. Mottles or iron plans and segregations and concretions form where the iron in solution meets oxygen again regularly and turns solid again and rusty again.

Soil Drainage	Description
Well drained	Well drained soils do not get waterlogged for more than 2-3 days at any time during the year. Highly Productive Land mostly contains well-drained soil. This is the land considered to be easiest to produce a wide range of primary produce from. The well drained soil category includes soils that are very rapidly permeable with a loamy sand or sandy texture, that in old definitions would have been considered "somewhat excessively drained". This includes soils on young sands dunes and soils on some pumice country. Such land can need frequent irrigation to reach maximum production, which can limit its the sustainability of land use(s) being considered.
Moderately well drained	Moderately-well drained soils get waterlogged up to about 60cm from the soil surface. Most shallow and moderately deep rooting crops and most trees find these soil drainage conditions ideal for growth because tap roots can forage for water but feeder roots can get plenty of oxygen of water from soil pores near the surface.
Imperfectly drained	Imperfectly drained soils are a lot more versatile than poorly drained soils. Most shallow rooting crops and most trees find these soil drainage conditions ideal for growth because tap roots can forage for water but feeder roots can get plenty of oxygen of water from soil pores near the surface.
Poorly drained	Poorly drained soils are grey under the topsoil. They are wet in winter. They get pugged up and are harder to cultivate than better drained soils. Poorly drained soils are found in wetlands and are an important source of mahinga kai. Poorly drained soils are sometimes artificially drained. High value horticultural crops can be very sensitive to poor soil drainage. It is important to site specific soil mapping to look for poor drainage when establishing horticultural crops like Kiwifruit, which can die if water tables are high at bud-break.
Very poorly drained	Only Organic soils (peat) are classified as very poorly drained. For peat to form, water has to sit for long periods of time at or above the soil surface. Peat soils are wetlands, and taonga as important ecological habitats, nutrient filters, and act as buffers in stream networks to slow flood-flows. They are an important source of biodiversity and mahinga kai.

Soil texture terms

The size of the particles of sediment or organic matter in a soil.

Soil Texture	Soil Description
Sandy	Gritty feel. Raspy sounding. Water tends to permeate through the soil rapidly and tends to be drought-prone.
Silty	Silky feel. Soil makes popping sounds and leaves ridges on fingers when worked. Water tends to permeate through the soil at a moderate speed. Tends to hold moisture available for plants.
Clayey	Sticky, buttery feel. Sticks to fingers and makes long worms and mouldable balls than can be polished. Water tends to permeate through the soil slowly. The soil tends hold onto a lot of water but not all is available to plants.
Loamy	A mixture of sand, silt and clay.
Peaty	Greater than 18% carbon. Best determined with soil test sent to a laboratory. Soil dark in colour, lightweight and crumbly.

Soil clay terms

Soils texture can be measured by clay percentages.

Soil clay percentage	Soil clay description
Sandy	Less than 18% clay. Soil feels gritty and sounds raspy. It may fall a ball when moist but it won't take a polish. Can't form a ribbon more than 1cm long or make a worm than can be bend into a circle. These soils are fragile and prone to erosion when cultivated.
Silty or Loamy	Between 18% and 35% clay. These soils are silky feeling when moist and worked. They make popping sounds and leave ridges on your fingers. These soils tend not to be as readily pugged or damaged by cultivatation, especially if they have high amounts of organic matter in them. If Allophanic soil material is present they are even more resilient.
Clayey	>35% clay. Soil is buttery or sticky when worked. Hard to cultivate or drive on when it gets wet. Pugs easily. The exception is soils that have a small amount of Allophanic material in them that make the soil aggregates more resilient e.g. Pukekohe Hill, and around Kerikeri.

Soil permeability terms

Soils permeability is affected by texture, structure and density.

Soil permeability	Measure	Soil permeability description
Very slowly permeable	<4mm/h	Coarse-structured, clay-rich soils where the soil pores have been blocked up and water can't drain down through the soil profile. Water tends to sit on the soil surface (ponding), or above slowly permeable layers in the soil (perched water tables). If there is a perched water table there will be a grey layer above a layer that is not grey underneath. Sometimes water can leach via "bypass flow" through a few large cracks in the soil.
Slowly permeable	<4mm/h	Coarse-structured clay-rich soils where the soil pores have been mostly blocked up and water can't drain down through the soil profile. Water often sits on the soil surface (ponding), or above slowly permeable layers in the soil (perched water tables). If there is a perched water table there will be a grey layer above a layer that is not grey underneath. Sometimes water can leach via "bypass flow" through a few large cracks in the soil.
Moderately permeable	4-72mm/h	Moderately well developed structure with loamy soils where pores are not blocked up and water can permeate though the soil. Water does not tend to pond on the soil surface or move through the soil via large cracks. Instead the soil moves through the fine material in the soil (matrix flow).
Rapidly permeable	>72mm/h	Sandy loamy or loamy sandy textured soils. May be stony. These soils have high numbers of pores that move large amounts of water through the soil quickly.
Very rapidly permeable	>72mm/h	Sandy textured soils or very stony soils with a sandy loam, loamy sandy, or sandy matrix between the stones. These soils tend to get droughty very quickly when it doesn't rain or during hot, windy periods.

Slope terms

Slope	Category	Degree of tilt	Description
Flat to gently undulating	A	0-3°	Horticultural machinery could operate on these angles
Undulating	B	4-7°	Some of this land is too steep for some horticultural machinery but this is croppable land from a slope perspective
Rolling	C	8-15°	This is croppable land from a slope perspective. This land should be cropped parallel to the contour for soil conservation purposes.
Strongly rolling	D	16-20°	This is croppable land from a slope perspective but it is dangerous to cultivate parallel to the contour. This should only be cropped occasionally. Cropping should be avoided with some highly erodible soils.
Moderately steep	E	21-25°	This land is too steep to cultivate with wheeled machinery but can operate two wheeled farm bikes and horses.
Steep	F	26-35°	Too steep for farm bikes.
Very steep	G	>35°	Accessible by walking only.

Soil terms associated with rainfall

Term	Description
Seasonal range in rainfall	Seasonality of rainfall is important for determining the variation of rainfall in El Nino compared with La Nina climate phases, especially with the backdrop of advanced climate change beginning to impact upon Aotearoa now.

Predicted patterns of soils according to annual average rainfall	Description
<500mm/yr	Semi-Arid Soils (on their way to being part of a desert). The salt in the soil can't wash out because it is too dry.
500-1,050mm/yr	Summer-dry soils. Often hard pans in the soil.
>1,050-1,400mm/yr	Soils in generally summer-safe landscapes. Generally well structured, deep soils where the landforms allow it.
>1,400mm/yr	Soils that are generally acid with nutrients and iron washed (or "leached") out of them because of the high rainfall

Terms associated with Peas

Term	Description
Arable crop	An arable crop means that it is planted in a field after it has been plowed (for example, wheat and peas)
Legume	A legume is a plant in the family Fabaceae, or the fruit or seed of such a plant (for example a garden pea, or a fava bean)
Pulse	A dry legume (for example, dried peas)

Terms associated with Wine

Term

Description

Viticulture
The science of growing grapes

Other terms

Term	Description
First & Last Frost	Maps of the date of the year of the first and last frost are important for determining what sensitive crops can be grown in an area. This is especially important in an era of global warming when plants such as bananas, pineapples, peanuts and coffee are being planted in Te Tai Tokerau, east of Opotiki and Tairawhiti.
Mean Annual Temperature	Maps of the date of the year of the first and last frost are important for determining what sensitive crops can be grown in an area. This is especially important in an era of global warming when plants such as bananas, pineapples, peanuts and coffee are being planted in Te Tai Tokerau, east of Opotiki and Tairawhiti.
Heat Units or Growing Degree Days	Heat units are an index calculated from air temperature to estimate growth and development of certain crops and pests during the growing season. They can be used to calculate the current growth stage of a crop, or to forecast when a crop will reach a certain growth stage. Heat units are calculated in hourly increments then totalled together over a year or a growing period.
Chill Units	Chill units are an index calculated from air temperature to estimate fulfilment of plant dormancy needs to begin spring growth. Chill units are particularly useful for fruit trees crops. Chill units are calculated hourly increments then totalled together over a year or a growing period.
Sunshine Hours	Sunshine hours are the total of how many sun-hours shine on a site over a year. One "sun-hour" is 1,000 watts of energy shining on 1 square metre of land surface for 1 hour. Generally places in lower latitudes like Southland (around 1,800 hours) and areas at high elevation in the west near mountains where orographic effects have a high impact have lower sunshine hours and places like Whakatane, Nelson and Blenheim have higher sunshine hours (e.g. 2,700 hours).