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Soil health is a state of a soil meeting its range of ecosystem 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 ecosystem 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 statusNRCS 2013 but tends to be confined largely to agronomic objectives. Soil health depends on soil biodiversity (with a robust soil biology), 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 they are not used in excess, and if they bring about a general improvement of overall plant growth which contributes more carbon-containing residues to the soil.
The phrase "soil health" has largely replaced the older "soil quality". The primary difference between the two expressions is that soil quality was focused on the ability of the soil serve a particular purpose, as in "quality of soil for maize production" or "quality of soil for roadbed preparation" and so on. The word "health" shifted the perception to be an integrative, holistic, and systematic view of the soil's ability to function as a self-sustaining system. 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 soil fertility 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 is large: in temperate grassland soil the bacterial and fungal biomass have been documented to be 1–/hectare and 2–/ha, respectively. Some microbiologists now believe that 80% of soil nutrient functions are essentially controlled by microbes. The Role of Soil Biology in Improving Soils Webinar
Using the human health analogy, a healthy soil can be categorized as one:
This translates to:
An unhealthy soil thus is the simple converse of the above.
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. Both these services combine physical (aggregate stability), chemical (mineral balance), and biological (CO2 respiration) analyses, 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 ("CO2-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 because the established metric of soil fertility is largely based on models constructed from "crop response" studies, which match crop yield to specific chemical nutrient concentrations, and no similar models 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), 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 ( and ) 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.Estimating Soil Carbon, Nitrogen, and Phosphorus Mineralization from Short-Term Carbon Dioxide Respiration Communications. in Soil Science and Plant Analysis, 39: 2706–2720, 2008Soil CO2 respiration: Comparison of chemical titration, CO2 IRGA analysis and the Solvita gel system. Renewable Agriculture and Food Systems: 23(2); 171–176
RA's primary contributions to soil health is the enhancement of organic matter and microbial activity. A myriad of practices can be used to increase soil organic content, like cover cropping, composting, and crop rotation to improve soil fertility, water retention, and ability to resist soil erosion. Research supports that soil microbial diversity is critical for maintaining fertility and resilience against the changing climate, and regenerative practices have been shown to enhance and support this biodiversity. Cover crops act as a protective blanket during the winter months, preventing compaction and erosion, while their roots maintain soil structure and nurture microbial diversity. Crop rotation further enriches soil microbiomes by diversifying nutrient and microbial inputs, disrupting pest cycles, and decreasing reliance on chemical inputs. Similarly, no-till farming minimizes physical disturbances to the soil, preserving its structure and improving water infiltration while conserving organic matter and keeping carbon in the soil, and not in the atmosphere. Permaculture is a design philosophy often incorporated into RA due to its focus on sustainable, ecosystem-based farming practices. Permaculture supports soil health by fostering natural nutrient cycles through techniques like companion planting, mulching, and perennial cropping. It emphasizes the creation of agricultural systems that model and mimic natural ecosystems, promoting biodiversity, more efficient resource use, and long-term soil health. These practices minimize soil erosion, enhance organic matter, and encourage beneficial microbial activity.
Regenerative agriculture offers significant economic and community benefits as well, nurturing resilient farming systems that enhance local economies and promote social well-being. Economically, RA reduces input costs by minimizing reliance on chemical fertilizers and pesticides, leading to lower operational expenses and increased profitability for farmers. Enhanced soil health from practices such as cover cropping and composting improves crop yields and market quality, which can provide greater productivity and financial stability. Although, the lack of heavy machinery increases the amount of necessary labor and steepens dependence on workers. Additionally, RA is designed to support community health by improving access to fresh local produce and working to alleviate food insecurity. Through RA, Community Supported Agriculture (CSA) systems can be established to bridge the divides between farmers and consumers, strengthen community ties, and facilitate a direct-market relationship. These practices not only sustain farmers but benefit surrounding communities by promoting sustainable livelihoods and resilience to environmental changes.
RA also addresses climate challenges by promoting carbon sequestration through practices like and no-till farming. These methods not only mitigate climate change by lowering atmospheric CO2 levels but also improve soil health, boosting soil productivity and resilience (Mishra et al. 295-309). Increasing soil organic carbon through RA practices has measurable effects on reducing atmospheric CO2 levels while improving soil functionality. The addition of organic material increases levels of soil organic carbon, thereby reducing atmospheric CO2 levels and enhancing soil fertility and productivity.
These practices collectively cultivate a resilient soil ecosystem that supports plant growth, enhances pest and disease resistance, and mitigates greenhouse gas emissions through carbon storage. However, despite its many benefits, RA faces challenges in assessment and widespread adoption. Biological indicators of soil health are often underrepresented in current evaluations due to their complexity and the context-specific knowledge required, as biological indicators of soil health often require context-specific ecological knowledge and are not universally standardized. Addressing these gaps and advancing research into RA's ecological and socioeconomic impacts will be crucial for its broader implementation and success.
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