Measuring Soil Health: A Western and Māori Approach
Soil and Environmental Science| Nargiss Taleb
Matariki marks a special time of year to reflect and celebrate the incoming new year, however it also marks a time to acknowledge our connection to the natural world. Each of the seven stars of Matariki hold their own significance and relation to our world – Tupu-ā-nuku symbolises anything in relation to soil such as plants that can be used to produce kai (food), rongoā (medicine) and kākahu (clothes) [1]. Reflection on this star reminds us of the value of the whenua and its ability to support us. Like Tupu-ā-nuku, soil plays a vital role in sustaining ecosystems and connecting us to our whakapapa. Soil health is thus of great importance and should be carefully managed, especially in our modern world where it faces significant challenges like erosion and pollution. There are many ways to understand the health of the soil and these will be explored here through both a western (conventional) and Te Ao Māori lens.
Healthy soil is important to sustain life however defining quality soil is often quite abstract as it depends on factors external to the soil itself – land use, political and socio economic priorities, soil management practices and ecosystem interactions [2]. Measuring the health of the soil however can be assessed more broadly in respect to the specific functions of the soil. Soil functions themselves cannot be directly measured through conventional science and thus aims to select specific properties of soil that can be measured. Māori soil health indicators however aim to fill in this space with understanding the soil from a more subjective point of view that addresses soil functionality itself. Both approaches are important and should be used simultaneously to gain a more complete understanding of soil health, combining measurable tests with Māori knowledge that reflects the connections between soil, people, and the environment.
Conventional soil health indicators aim to cover the fine balance between soil productivity, environmental quality and flora/fauna health. The indicators can be split into 3 broader categories – physical, chemical, and biological (Figure 1).
Figure 1: Examples of soil health indicators. Adapted from Maanaki Whenua | Landcare Research [3]
Physical properties of soil are important as they not only physically support flora but also supplies all the necessary water and nutrients to the roots of plants. Bulk density, microporosity and aggregates all relate to each other strongly. The density of soil tells us how compact the soil is and thus inherently how porous and how soil particles are structured (Figure 2). The aggregates are where silt and sand are held together by other soil components like clay. In between aggregates are macro and micropores, which allow for movement of air and water. Very large macropores allow roots to grow more efficiently and provide a supportive environment for beneficial soil organisms, whereas compacted soil reduces or, in extreme cases, completely inhibits these benefits [4].
Figure 2: An example of soil structure. [5]
Chemical indicators tell us more about how particular reactions and processes occurring in the soil may be impacted. Soil pH for example, controls the solubility of nutrients and chemicals in soil water and thus their availability to be taken up by plants and exposure to microorganisms. Maintaining a good balance with pH is important as very acidic or alkaline soils can have variable implications for the health of the soil. More acidic soils generally favour plant growth due to more micronutrient availability [6], however in strongly acidic soils (pH <5), higher metal concentrations can cause toxicities alongside deficiencies (calcium, magnesium) [7]. Contrary to this, alkaline soils show a big reduction in macronutrient availability such as phosphorus – an important nutrient for younger plants as it aids in plant growth. Alongside this, many metals like cadmium and nickel are far less mobile and are more likely to be retained in the soil [8]. Another important chemical indicator is the occurrence of trace pollutants and other contaminants. This could be as simple as heavy metals that are naturally occurring but may have differing concentrations due to anthropogenic activity, to more complex chemicals like per- and polyfluoroalkyl substances (PFAS), and dioxins through pesticide applications or microplastics. Substances like these can influence soil processes and have toxicological effects on microorganisms—some of which are well studied, while many other emerging pollutants remain largely unexplored.
Biological indicators are often the more costly and labour-intensive aspects of soil health. There are multitudes of biota within the different layers of the soil which all play different roles in the ecosystem, these all adapting from the stressors in the environment. Because of this constant dynamic change, it is difficult to interpret what constitutes a ‘healthy level’ of organisms and how diverse it should be. As a result, properties like organic matter fractions, respiration and mineralizable nitrogen as a surrogate for biological processes mediated by organisms [9]. Mineralizable nitrogen refers to how much of the organic nitrogen is being converted (often by microbes) to mineral forms which are more available to plants. Other measures like total organic carbon and nitrogen can tell us more about the sources of organic matter in the soil as well as their productivity [10].
Te Ao Māori looks at the health of soil a little differently, not only looking towards what functions the ecosystem provides but also the interconnectedness between the environment and people. Manaaki Whenua | Landcare Research, currently employs 4 provisional Māori soil health indicators, mauri, mana, mahinga/maara kai and oranga ora [11]. Mauri relates to the essence and life force behind the soil, with the idea that healthy soil should be fit for sustaining life, health and prosperity. This means there should be well-functioning ecosystems full of biota and acknowledgment of the interconnections between people and the physical/chemical/biological components of soil [12]. Mana relates to prestige or authority, recognising management rights to resources, land and soil. This can include honouring the Treaty of Waitangi and other iwi/hapu/whanau land ownership interests. Mahinga/maara kai principles refer to the food bearing properties of the land and the ability to provide sustenance, food sovereignty and prosperity [11]. Evidence of this indicator can come from the production of healthy kai (food). The last of the provisional indicators is oranga ora, measuring the safety of food that’s grown from the soil. Healthy soil will yield healthy food, which in turn leads to healthy people; thus, oranga ora follows tikanga (practices/guidelines) to prevent harmful contaminants and waste from affecting good-quality soil.
Other principles that are important include whakapapa, wairua and Taonga Tuku Iho [13]. Whakapapa shows respect for ancestral lineage, connecting soil back to ancestors and origins. It also establishes a metaphysical place, helping us to understand the source of where soil may have come from. More spiritually, wairua provides balance between mauri and mana, ensuring there is a healthy interconnectedness between the spirit of a person and the physical state of soil [12]. Wairua allows for a balanced ecosystem as kaitiakitanga (guardianship/protection) and karakia (prayers) can be implemented. The last principle, Taonga Tuku Iho, relates to sustainability of soil as a resource. Soil must be used equitably and responsibly, ensuring that this vital resource is maintained and ideally enhanced, benefiting future generations.
Understanding soil health should require a holistic approach, integrating both the conventional scientific indicators and Te Ao Māori standpoints. Whilst physical, chemical and biological indicators may be able to easily measure functionality of the soil, Te Ao Māori emphasizes deeper and important connections that people have with the environment. Whether it is assessing nutrient availability or soil’s ability to sustain life, maintaining the integrity and health of soil is essential for sustaining ecosystems and creating resilient communities.
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[7] Queensland Government, “Soil pH | Environment, land and water | Queensland Government,” Qld.gov.au, Sep. 24, 2013. https://www.qld.gov.au/environment/ land/management/soil/soil-properties/ ph-levels https://espacepourlavie.ca/en/ soil-structure (accessed Feb. 4, 2025).
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[9] U.S. Department of Agriculture, Natural Resources Conservation Service, “Soil biological indicators: An overview of key biological indicators for soil health,” Oct. 2022. [Online]. Available: https://www.nrcs. usda.gov/sites/default/files/2022-10/ biological_indicators_overview.pdf. (accessed: Feb. 4, 2025).
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[11] “Māori indicators of soil health,” Manaaki Whenua, 2025. https://www.landcareresearch.co.nz/discover-our-research/land/ soil-and-ecosystem-health/soil-healthand-resilience/kaupapa-maori/maori-indicators-of-soil-health/ (accessed Feb. 04, 2025).
[12] G. Harmsworth, T. Arawa, N. Tūwharetoa, and N. Raukawa, “The Mana of Soil: A Māori Cultural Perspective of Soil Health in Aotearoa-NZ.” Available: https://www. landcareresearch.co.nz/assets/Events/ Link-series/Mana_Soil.pdf (accessed Feb. 04, 2025).
[13] “Key Māori principles,” Manaaki Whenua. https://www.landcareresearch.co.nz/ discover-our-research/land/soil-and-ecosystem-health/soil-health-and-resilience/ kaupapa-maori/key-maori-principles/ (accessed Feb. 04, 2025).
Nargiss is a first-year PhD student focused on applying chemistry to tackle environmental challenges. Her research focuses on compostable packaging, contaminants (PFAS, microplastics), and their environmental impacts. She is passionate about science communication, and has a large houseplant collection, and enjoys spending time hiking Aotearoa’s wilderness.