Soil health is a state of a
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...
meeting its range of
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
functions as appropriate to its environment. In more colloquial terms, the health of soil arises from favorable interactions of all soil components (living and non-living) that belong together, as in microbiota, plants and animals. It is possible that a soil can be healthy in terms of eco-system functioning but not necessarily serve crop production or human nutrition directly, hence the scientific debate on terms and measurements.
Soil health testing is pursued as an assessment of this status but tends to be confined largely to agronomic objectives, for obvious reasons. Soil health depends on
soil biodiversity (with a robust
soil biota), and it can be improved via
soil management, especially by care to keep protective living covers on the soil and by natural (carbon-containing) soil amendments. Inorganic fertilizers do not necessarily damage soil health if 1) used at appropriate and not excessive rates and 2) if they bring about a general improvement of overall plant growth which contributes more carbon-containing residues to the soil.
Aspects
The term soil health is used to describe the state of a soil in:
*Sustaining plant and animal productivity (agronomic focus);
*Enhancing
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity' ...
(
Soil biodiversity) (ecological focus);
*Maintaining or enhancing
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
and
air quality
Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...
(environmental/climate focus);
*Supporting
human health and
habitation
Habitation may refer to:
* Human settlement, a community in which people live
* Dwelling
In law, a dwelling (also known as a residence or an abode) is a self-contained unit of accommodation used by one or more households as a home - such as ...
.
*
sequestering carbon
Soil Health has partly if not largely replaced the expression "Soil Quality" that was extant in the 1990s. The primary difference between the two expressions is that soil quality was focused on individual traits within a functional group, as in "quality of soil for
maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn ( North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. ...
production" or "quality of soil for
roadbed preparation" and so on. The addition of the word "health" shifted the perception to be integrative,
holistic and systematic. The two expressions still overlap considerably. Soil Health as an expression derives from organic or "biological farming" movements in Europe, however, well before soil quality was first applied as a discipline around 1990. In 1978, Swiss soil biologist Dr Otto Buess wrote an essay "The Health of Soil and Plants" which largely defines the field even today.
The underlying principle in the use of the term “soil health” is that soil is not just an inert, lifeless growing medium, which modern intensive farming tends to represent, rather it is a living, dynamic and ever-so-subtly changing whole environment. It turns out that soils highly
fertile
Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Ferti ...
from the point of view of crop productivity are also lively from a biological point of view. It is now commonly recognized that soil
microbial biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms biom ...
is large: in temperate grassland soil the bacterial and fungal biomass have been documented to be 1–/
hectare
The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
and 2–/ha, respectively.
Some microbiologists now believe that 80% of
soil nutrient functions are essentially controlled by microbes.
Using the human health analogy, a healthy soil can be categorized as one:
*In a state of composite well-being in terms of biological, chemical and physical properties;
*Not diseased or infirmed (i.e. not
degraded, nor degrading), nor causing negative off-site impacts;
*With each of its qualities cooperatively functioning such that the soil reaches its full potential and resists degradation;
*Providing a full range of functions (especially nutrient,
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...
and
water cycling) and in such a way that it maintains this capacity into the future.
Conceptualisation
Soil health is the condition of the soil in a defined space and at a defined scale relative to a set of benchmarks that encompass healthy functioning. It would not be appropriate to refer to soil health for soil-roadbed preparation, as in the analogy of soil quality in a functional class.
The definition of soil health may vary between users of the term as alternative users may place differing priorities upon the multiple functions of a soil.
Therefore, the term soil health can only be understood within the context of the user of the term, and their aspirations of a soil, as well as by the boundary definition of the soil at issue. Finally, intrinsic to the discussion on soil health are many potentially conflicting interpretations, especially ecological landscape assessment vs agronomic objectives, each claiming to have soil health criteria.
Interpretation
Different soils will have different benchmarks of health depending on the “inherited” qualities, and on the geographic circumstance of the soil.
The generic aspects defining a healthy soil can be considered as follows:
*“Productive” options are broad;
*Life diversity is broad;
*Absorbency, storing, recycling and processing is high in relation to limits set by
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologica ...
;
*
Water runoff quality is of high standard;
*Low
entropy
Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodyna ...
; and,
*No damage to, or loss of the fundamental components.
This translates to:
*A comprehensive cover of
vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic charact ...
;
*Carbon levels relatively close to the limits set by
soil type and climate;
*Little leakage of nutrients from the ecosystem;
*Biological and
agricultural productivity relatively close to the limits set by the soil environment and climate;
*Only geological rates of
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...
;
*No accumulation of
contaminants; and,
An unhealthy soil thus is the simple converse of the above.
Measurement
On the basis of the above, soil health will be measured in terms of individual
ecosystem services provided relative to the benchmark. Specific benchmarks used to evaluate soil health include CO
2 release, humus levels, microbial activity, and available calcium.
Soil health testing is spreading in the United States, Australia and South Africa.
Cornell University, a land-grant college in NY State, has had a Soil Health Test since 2006. Woods End Laboratories, a private soil lab founded in Maine in 1975, has offered a soil quality package since 1985. Bost these services combine test for physical (
aggregate stability) chemical (mineral balance) and biology (CO
2 respiration) which today are considered hallmarks of soil health testing. The approach of other soil labs also entering the soil health field is to add into common chemical nutrient testing a biological set of factors not normally included in routine soil testing. The best example is adding biological
soil respiration
Soil respiration refers to the production of carbon dioxide when soil organisms respire. This includes respiration of plant roots, the rhizosphere, microbes and fauna.
Soil respiration is a key ecosystem process that releases carbon from the so ...
("CO
2-Burst") as a test procedure; this has already been adapted to modern commercial labs in the period since 2006.
There is however resistance among soil testing labs and university scientists to add new biological tests, primarily since interpretation of soil fertility is based on models from "crop response" studies which match yield to test levels of specific chemical nutrients, and no similar models for interpretation appear to exist for soil health tests. Critics of novel soil health tests argue that they may be insensitive to management changes.
Soil test methods have evolved slowly over the past 40 years. However, in this same time USA soils have also lost up to 75% of their carbon (
humus
In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...
), causing biological fertility and ecosystem functioning to decline; how much is debatable. Many critics of the conventional system say the loss of soil quality is sufficient evidence that the old soil testing models have failed us, and need to be replaced with new approaches. These older models have stressed "maximum yield" and " yield calibration" to such an extent that related factors have been overlooked. Thus, surface and
groundwater pollution with excess nutrients (
nitrates and
phosphates) has grown enormously, and early 2000s measures were reported (in the United States) to be the worst it has been since the 1970s, before the advent of environmental consciousness.
Soil health gap

Importance of soil for global food security, agro-ecosystem, environment, and human life has exponentially shifted the trends of research towards soil health. However, lack of a site/region specific benchmark has limited the research effort towards understanding the true effect of different agronomic managements on soil health. In 2020, Maharjan and his team, introduces a new term and concept "Soil Health Gap" and described how native land in particular region can help in establishing the benchmark to compare the efficacies of different management practices and at the same time it can be used in understanding quantitative difference in soil health status.
See also
*
Dryland salinity
*
Ecosystem services
*
Soil aggregate stability
*
Soil biodiversity
*
Soil carbon
*
Soil fertility
Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent Crop yield, yields of high quality.
*
Soil functions
*
Soil policy (Victoria, Australia)
*
Soil quality
*
Soil resilience
Soil resilience refers to the ability of a soil to resist or recover their healthy state in response to destabilising influences. This is a subset of a notion of '' environmental resilience''.
Overview
Soil resilience should first be looked at ...
*
Soil structure
*
Soil water (retention)
References
Further reading
*
*
*
*
External links
Improving Soil pH, Reducing Soil Born Disease and Improving Crop ProductionLiving Soils(Greenpeace)
NRCS Soil Health and NPK(NRCS)
NRCS Soil Health in Field and Forage Crop Production(NRCS)
WEBINARS on SOIL HEALTHSoil Quality Indicator SheetsNational Look at Groundwater Pollution(USGS)
{{Natural resources
Land management
Health
Health, according to the World Health Organization, is "a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity".World Health Organization. (2006)''Constitution of the World Health Organiza ...
Soil science