Understanding Soil Health Concept Interpretation Scientific evolution Significance
Understanding soil health
Natural soil is an ecosystem consisting of minerals, organic matter (OM), living organisms, water, and air and maintaining an unceasing
flow of matter and energy within and with the surrounding environment via various physical, chemical, and biological processes (Guo, 2021). It
is also through these processes such as water retention, chemical oxidation, and microbial decomposition that natural soil functions to support
plant growth, regulate water movement and purify water, decompose organic wastes and recycle nutrients, harbor organisms, and buffer
environmental changes. The capability of a soil to perform these environmental functions and provide according ecosystem services, however, is
determined by the efficiency of the soil to carry out the intrinsic physical, chemical, and biological processes under particular geographic
and climate conditions and is indicated by “soil health” (Guo, 2021).
Soil health is defined as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans.”
A lengthier version of the definition is as “the capacity of soil to function as a vital living system, within ecosystem and land-use boundaries,
to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health”. In brief, soil health
indicates the capability of a soil to furnish ecosystem services. The health of a soil reflects how well the soil can carry out its environmental
functions. A soil is evaluated “healthy” if it provides comparable or better ecosystem services relative to undisturbed reference soils of the
similar type in the same region. Otherwise the soil is unhealthy, unable to perform the normal environmental functions of the like soils in the
inherent ecosystem.
Soil health is a comprehensive expression of the relevant soil physical, chemical, and biological properties (Figure 1). Figure 1. Soil health as a comprehensive expression of various soil properties
The current concept of soil health was evolved in 1990s from “soil quality” referring to “the capacity of a soil to function within ecosystem
and land-use boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal health.”
The term was first mentioned by Mr. Henry A. Wallace in 1910 in an unpublished thesis to describe soil fertility (Guo, 2021). In 1936 USDA
published a document entitled “Soil Health and National Wealth” to promote soil fertility and nutrient management. The U.S. farmers started
to adopt the term in 1990s, motivating the scientific community to re-define soil health. The term became popular in the 2010s, presumably
a result of the 2007–2008 global food crisis and the recognition of soil’s carbon (C) sequestration potential for mitigating climate change.
The term declares that soil is a living entity in analogy with an organism or a community that can be evaluated by healthiness. As an ecosystem,
soil can be healthy or unhealthy, depending on how well the ecosystem is maintained and its stability, resilience, and stresses are
self-regulated.
The scientific system of soil health covers primarily three aspects: concept, assessment, and management (Figure 2). Figure 2. Development of the science of soil health on concept, assessment, and management as the three
focal areas. SMAF: Soil management assessment framework; CASH: Comprehensive assessment of soil health; SHAPE: Soil health assessment protocol
and evaluation
The health status of an agricultural soils is illustrated by its actual capacity relative to that of a population of like soils in the same
region for sustaining a satisfactory crop productivity through maintaining desirable nutrient cycles, soil structure, C transformation, and
pest and disease regulations. Healthy agricultural soils are usually characterized by a higher-than-average crop productivity, sufficient
supply of nutrients, appropriate OM contents, right tilth and drainage, dominating presence of beneficial organisms over pathogens, high
resistance to erosion and degradation, and being contamination-free (Guo, 2021). Compared with less healthy ones, healthier soils generally
demonstrate a wider working ranges and a higher input-to output conversion efficiency.
Soil (health) degradation is “the loss of the intrinsic physical, chemical, and/or biological qualities of soil either by natural or anthropic
processes, which result in the diminution or annihilation of important ecosystem functions”. Land uses, disturbances, and management practices
may alter soil properties and subsequently, impact soil health. Tillage, for example, deteriorates soil structure and promotes OM
mineralization, leading to significant health degradation of cropland soil.
Healthy soil is the foundation of sustainable agriculture. To promote the vitality of soil and enhance the soil health of agricultural lands
from the federal policy perspective, USDA-NRCS Soil Health Division was created in 2014. The Soil Health Institute was founded in 2016 as a
U.S. non-profit organization to facilitate soil health research and scientific advancement. The European Commission formed the Mission Board
for Soil Health and Food in 2019 to develop the interim targets and long-term goals on soil health and food as “ensure that 75% of soils are
healthy by 2030 and are able to provide essential ecosystem services”. In Australia, the former Governor General has been appointed by the
Minister for Agriculture and Water Resources since 2013 as the National Advocate for Soil Health to promote the science and practice of soil
health in collaboration with the non-profit organization Healthy Soil Australia. Worldwide, an open, dynamic database (SoilHealthDB) has been
initiated to collect and store global soil health data. The concept of soil health has been gradually embraced by farmers, soil
conservationists, and policymakers around the world (Guo, 2021).
Guo, M. 2021. Soil health assessment and management: recent development in science and practices. Soil Syst.
5, 61. doi: 10.3390/soilsystems5040061
Concept
