Soil Health
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6.3 Soil Quality
In the world today, soil quality is poor in many locations. Low concentrations of nutrients and organic carbon result in lower yields. Salinity is an
issue in locations where irrigation water has contributed to an increase in salt
concentration. In this book, the emphasis is on applications of phytoremediation at contaminated sites. Many of these sites have physical issues because
water-holding capacity is poor, porosity is low, and root penetration is difficult because of compaction. Both soil contamination and degraded soil quality must be addressed at many sites.
Soil tilth, the physical state of the soil for growing plants, often needs to
be improved at many sites where phytoremediation is used to address contamination. The conditions at the soil surface and the conditions up to 20 cm
below the surface are important for establishing vegetative cover. Good soil
drainage and beneficial populations of bacteria, fungi, earthworms, nematodes, and other organisms are desirable (Chauhan & Mittu, 2015).
Assessment approaches of soil quality and indicators of soil health have
been reviewed with respect to soil threats, ecosystem services, and functions
(Bünemann et al., 2018). A total of 65 sets of indicators were reviewed; organic
carbon, pH, available nitrogen, phosphorus and potassium, water storage,
texture, and bulk density were included more than all other indicators.
Biological indicators are important but are less commonly included in assessments because of the skills needed; however, including them can improve
assessment results. The interpretation of assessment results requires experimental expertise or information on each test and its desired range of values.
It is useful to be able to relate the ecosystem services to the values of the
measured variables.
The United Nations Sustainable Development Goals include goal 2, which
is zero hunger, and goal 15, which is life on land (sustainably manage forests, combat desertification, halt and reverse land degradation, and halt biodiversity loss). This goal 15 includes improving the health of ecosystems by
addressing soil health to improve livelihoods. As population increases and
quality of life improves, there is a great need to improve soil quality and the
productivity of ecosystems that benefit from good soil health. As the effort to
reduce greenhouse gas emissions advances and the transition to biodegradable products expands, land is needed for many purposes, and good soil
health should become a priority for all countries.
The Food and Agriculture Organization (FAO) estimates that about onethird of soils that are used for agriculture have poor soil quality because of
past use and management (FAO, 2011; Jian et al., 2020; Rodríguez-Eugenio
et al., 2018). Low soil fertility, nutrient depletion, loss of soil from erosion,
and low concentration of organic carbon are common reasons for poor soil
quality. In a national survey in China, 16.1% of soil samples had measured