Sunday Times 2
Healthy soil for healthy humans and a healthy planet
View(s):
Prof. Saman Dharmakeerthi and Hansika Lewkebandara
Whereas conventionally, soil is considered just simple dirt or mud, it is, in fact, a functional living system. It represents a complex dynamic natural resource that is essential to life on Earth. It can be defined as “the unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants”. It takes thousands of years for soil to form from the weathering of the parent rock material. But it takes only a few hours to destroy thus hardly formed soil.
The multi-functionality of soil
Soil supports the existence of plants, among many other functions. In regard to ecosystems, it contributes to the mediation of climate, hydrological, and biodiversity functions. Hence soil is a multifunctional natural resource and some of these functions include:
Nutrient Supply and Plant Growth: Soil is the chief repository of nutrients that plants need to grow. The common examples are macronutrients such as nitrogen, phosphorus, and potassium, and trace minerals like iron and zinc. Soil plays an important role in the short- and long-run nutrient supply by storing and releasing them slowly to plants to support their healthy growth.
Water Storage and Filtration: Healthy soils act like sponges in soaking up and storing water. By regulating the rates of water flow through an ecosystem, soils ensure the plants get just the right amount of moisture at any time while preventing flooding and runoff. The soils allow the filtration of rainwater and wastewater through them, eliminating contaminants and allowing clean water into the groundwater systems. Soil filtration is one of the essential activities in the maintenance of water quality.
Soil Carbon Sequestration: Soils are an important sink in terms of carbon and, hence, part of the solution to mitigate climate change. A big percentage of Earth’s carbon is held within the soil in organic matter form. Plants remove CO2 from the atmosphere by photosynthesis and store it in their roots and within the soil. This helps in reducing the amount of CO2 in the air and, to some extent, reduces the effect of climate change.
Biodiversity support: Soil is a habitat for a range of organisms, from microscopic bacteria and fungi to earthworms, ants, and other insects. These organisms break down organic material, aerate the soil, and contribute to nutrient cycling. A healthy soil ecosystem supports a diversity of life, which in turn contributes to the resilience of the environment as a whole.
Erosion Control: Soil has the ability to stabilise land by binding particles together and, therefore, preventing erosion caused by wind and water. Plant roots that grow in the soil make a closely knit network that will glue the soil particles, reducing the risk of soil erosion. Healthy soils further promote infiltration, reduce surface runoff, and help to maintain the integrity of the soil.
Is soil a living being?
In itself, yes, it can be considered a living thing. It may not, per se, be classically defined as alive; however, for sure, it houses a teeming, dynamic community of living organisms, and its health is in great measure determined by the interaction of these organisms with the soil environment. Soil teems with life-from bacteria and fungi to insects and larger organisms like worms. These microorganisms and organisms interact symbiotically in decomposing organic matter, nutrient recycling, and plant growth.
Soil health is inseparably related to planetary health. Pic courtesy fao.org
It consists of a food web of different organisms, vital for soil fertility and health. For example, large fauna such as insects, millipedes, rats, and snails break down dead plants into smaller pieces. Then earthworms and microorganisms such as bacteria and fungi, decompose dead plants and pieces into soil organic matter. Nutrients released during decomposition are utilised by plants. The earthworms burrow underground, enhancing the structure of the soil and providing a route through which air and water can reach the plant roots more easily. These living organisms regulate the conditions of soil and contribute towards soil health.
What is soil health?
Soil health refers to the ability of soil to function as a living ecosystem that sustains plants, animals, and humans. More precisely, healthy soil should be dynamic, balanced, and resilient. Healthy soil contains an optimum balance of physical, chemical, and biological properties. This allows soil to perform its numerous functions effectively in supporting plant growth, regulating water, cycling nutrients, and maintaining biodiversity.
Key indicators of healthy soil
As we measure the temperature using a thermometer to see whether we have fever, it is possible to conduct a wide range of physical, chemical, and biological tests to ascertain the health of the soil. The following are some of the common indicators that may show whether the soil is “healthy”.
Soil Structure: Healthy soil has good structure; this simply means it has a well-developed pore and aggregate network that can allow for aeration and water movement within the soil. The structure is appropriate for the growth of roots with access to nutrients. Soil that has become compacted becomes dense and hard, prohibiting roots from growing as well as preventing water infiltration. Compaction can be caused by heavy machinery, overgrazing, or excess tilling.
Organic matter: Serves to improve the structure, water-holding capacity, nutrition for plants and microbial existence. Organic matter usually constitutes about 3-6% in healthy soil and helps develop soil structure with a definite improved retention of nutrients.
Microbial Activity: Good soil is crawling with life. The healthy microorganisms, like bacteria and fungi or protozoa, are good and positive indicators of soil health because these help in organic matter decomposition, nutrient recycling, and promotion of plant health.
Water Retention and Infiltration: Healthy soils are capable of water retention to supply the plants and also of excess water drainage to avoid waterlogging. Easy erosion or runoff of soil upon rainfall signifies that it is not healthy. This usually happens when there is a lack of ground cover or an inadequacy in soil structure.
pH Balance: The pH level of the soil maintains the availability of nutrients within the soil to the plants. Highly acid or highly alkaline soils are not good for the growth of plants, whereas most plants grow very well in a neutral pH range of 6-7.
Nutrient Balances: When the soil is either too acidic or too alkaline, nutrient deficiencies or toxicities may be initiated, both of which would affect plant health. Excessive applications of synthetic fertilizers might also be a cause of nutrient imbalances and loss of soil microorganisms.
Sick soils make humans also sick
Sick soils not only affect plant health, but they also directly and indirectly affect human health. Poor fertility of the soil results in plant growth that is affected by nutrient deficiency; if such agricultural produce is consumed by humans, then it shows up as malnutrition and its related diseases. Besides, all kinds of chemical fertilisers and pesticides used vastly to counteract degradation, may contaminate food and water supplies, leading to chemical poisoning, disruption of hormones, and even increased risks for cancer. On the other hand, sick soils further promote environmental problems such as air pollution, water contamination, and climate change; all of these, in turn, affect human health through the quality of food, water, and air used.
Sick soils make the earth sick too
Soil health is inseparably related to planetary health: when soils deteriorate, they lose their carbon-sequestering ability and this carbon mixes into the atmosphere as carbon dioxide—one of the most potent greenhouse gases. Contributing to global warming and climate change, degenerated soil often results in poor water retention, causing floods in one region and drought in another. Other symptoms include soil erosion, where productive lands are lost and agricultural yields reduced, hence affecting food security. However, this makes the ecosystem increasingly less and less able to deal with stress. It leads to a loss in biodiversity and to a general reduction in Earth’s systems’ functionality. In this manner, sick soils create a vicious circle that denies health not only to the soil itself but also to the whole biosphere.
The four principles of
managing healthy soil
Key principles to be followed in maintaining and improving soil health are based on maximising the expressed performance of its functions while minimising the detrimental effects of agricultural practices. These principles are enumerated below.
1. Maximise the presence
of living roots
Living roots are a crucial element in soil health. They interact with soil microorganisms by feeding them, hence encouraging their activities. They help maintain the structure of the soil through the exudation of organic compounds that bind the particles of the soil together. Off-season cover cropping involves planting legumes or grasses to keep roots in the soil during the year. This prevents erosion, maintains fertility, and supports beneficial organisms living in the soil.
2. Minimise disturbance
Excessive disturbance through tilling and plowing degrades the structure, reduces organic matter, and disrupts the soil food web. Practicing minimum tillage technologies such as no-till or low-till allow soil to maintain natural structure and reduce chemical inputs. Reduced tillage prevents soil compaction, maintains organic matter, and helps protect the beneficial organisms that live in the soil.
3. Maximise soil cover
This is necessary to prevent erosion, inhibit water evaporation, and protect against extreme temperatures. Covering the soil with plants or organic residues reduces the loss of water and reduces wind and water erosion: cover crops like red clover, sun hemp, and pueraria protect the surface and bring additional organic matter into the soil. Straw, compost, crop residues and lawn clippings can be used for mulching so that soil structure can be improved while decomposing and gradually enriching the soil.
4. Biodiversity must be maximized
Soil health is greatly dependent on biodiversity. A good mix of plant species and microorganisms in the soil contributes to nutrient cycling, pest control, and disease prevention. Crop rotation, intercropping, and agroforestry practices will again enhance biodiversity, thus helping break the pest cycles, improving nutrient availability, and generally enhancing the resiliency of the soil.
Concluding remarks
Soil is a living, breathing system that provides life on Earth. Healthy soils are basic to food production, climate regulation, and the sustainability of ecosystems. In the face of global challenges that include climate change, food insecurity, and environmental degradation, the importance of healthy soil has never been clearer. It means the adoption of those best practices that put soil health first, such as maximising living roots, minimising disturbance, maximising soil cover, and increasing biodiversity for catalysing a future with prosperity for all humans along with a healthy planet.
Investment in soil health is an investment for humankind’s future. This is a commitment we must show to secure future generations. Healthy soil is more than the cornerstone of agriculture; it is a stepping stone toward a world that will be more sustainable and resilient.
(Prof. Saman Dharmakeerthi
is attached to the
University of Peradeniya;
Hansika Lewkebandara is a
postgraduate student at the University of Peradeniya)