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Soil health

earth science Maturity 11-13 Next article →

Soil health describes the capacity of a soil to function as a self-sustaining ecosystem within its specific environment. While people often think of soil as just a medium for growing plants, it is actually a living, dynamic, and ever-changing environment. A healthy soil is defined by the favorable interactions between its living components, such as microbiota, plants, and animals, and its non-living components. This state of health allows the soil to meet various ecosystem functions. These functions include sustaining plant and animal productivity, enhancing biodiversity, and maintaining high air and water quality.

SoilHealthConcept
SoilHealthConcept

The mechanism of soil health relies on complex biological, chemical, and physical processes. Central to this system is the cycling of nutrients, carbon, and water. Microbes, which are microscopic living organisms, play a massive role in these cycles. Some microbiologists believe that microbes control approximately 80% of all soil nutrient functions. In temperate grassland soils, the scale of this life is enormous. Bacterial biomass can reach 1 ton per hectare, while fungal biomass can reach 2 tons per hectare. These organisms process organic matter, which helps maintain the soil's structure and fertility through constant chemical and biological activity.

There are different ways to view the focus of soil health. An agronomic focus looks at how soil supports crop production and human nutrition. An ecological focus emphasizes soil biodiversity and the variety of life within the ground. An environmental or climate focus looks at how soil manages water and air quality, specifically through sequestering carbon. Sequestering carbon means the soil captures and stores carbon from the atmosphere. This process is vital for regulating the Earth's climate. Because different users have different goals, the benchmarks for what counts as "healthy" can vary depending on the context.

Historically, the way we talk about soil has changed significantly. Before the 1990s, scientists mostly used the term "soil quality." Soil quality was a narrow term used to describe how well soil performed a specific task, such as growing maize or providing a base for a road. The shift to "soil health" represents a more holistic and systematic view. This movement was influenced by organic and biological farming movements in Europe. A major milestone occurred in 1978 when Swiss soil biologist Dr. Otto Buess wrote "The Health of Soil and Plants." His work helped define the field by treating soil as a living whole rather than an inert medium.

Measuring soil health requires looking at specific ecosystem services and benchmarks. Scientists evaluate factors like CO2 release, humus levels, microbial activity, and available calcium. Modern testing often combines physical analysis, such as aggregate stability, with chemical mineral balance and biological respiration. One notable test is the "CO2-Burst," which measures biological soil respiration. In the United States, Cornell University has provided soil health testing since 2006. Woods End Laboratories in Maine has offered soil quality packages since 1985. These tests help determine if the soil is meeting its potential or if it is degrading.

One surprising and serious fact is the decline of soil carbon in the United States. Over the last 40 years, USA soils have lost up to 75% of their carbon, also known as humus. This loss causes biological fertility and ecosystem functions to decline. When soil loses its health, it can lead to negative off-site impacts. For example, excess nutrients like nitrates and phosphates can leak from the soil. This causes surface and groundwater pollution. In the early 2000s, pollution levels in the United States were reported to be the worst they had been since the 1970s.

To combat these issues, many use regenerative agriculture, which is a holistic approach to farming. This method focuses on feeding the soil rather than just feeding the plants. It uses practices like cover cropping, which provides a protective blanket of vegetation to prevent erosion. Crop rotation diversifies the nutrients and microbes in the soil. No-till farming minimizes physical disturbance to keep the soil structure intact. Permaculture is another design philosophy used to mimic natural ecosystems. These methods all aim to enhance organic matter and microbial activity to build a resilient, self-sustaining system.

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