The theme for World Soil Day 2023 – soil: where food begins – tells us most of what we need to know about the vital importance of this natural resource. The statistics are awe-inspiring and spine-chilling in equal measure, and clearly illustrate the link between soil health, food security and climate change:
- Only about 7,5% of the Earth’s surface consists of the agricultural soil on which food can be grown. This fragment competes with humankind’s other needs and wants, ranging from housing to entertainment, industrial and military complexes to landfill sites.
- 95% of our food comes from the soil.
- Agricultural production will have to increase by 60% to meet the global food demand in 2050; sustainable soil management could produce up to 58% more food.
- Soils supply 15 of the 18 naturally occurring chemical elements essential to plants.
- 25% of the planet’s biodiversity is found in its soils; one teaspoon of soil can contain more living organisms than there are people on the planet.
- Soil is the planet’s second largest carbon store.
- 33% of the Earth’s soils, and more than half of agriculture soils, are degraded.
- It takes more than 1 000 years to grow 1 cm of soil.
Some aspects of the value of soils cannot be expressed in numbers. For instance, the billions of bacteria that live in soils are critical to the development of antibiotics and other medicines. Healthy soils absorb and purify water for human consumption and regulate the impact of excess rainfall by preventing floods. This ecosystem service will only become more important as climate change causes increasingly erratic rainfall patterns.
Looking at food production specifically, healthy soils produce more nutritious food and give plants greater resilience to pests and diseases. Healthy soils hold more water and make it available to plants when rainfall is unreliable. Their ability to absorb heavy rainfall prevents the run-off of vital nutrients from fields.
“Soil health matters a great deal,” says Stefan van Zyl from Syngenta Seedcare South Africa. “The reality that the 10 – 30 cm of topsoil that sustains our ability to grow food could run out in just 60 years is a call to action not a single person or company can afford to ignore.”
The role of root health
The key to protecting and restoring soil health is a holistic approach. “In agriculture, the problem and indeed the solution lie in what we plant and when, and the cultivation practices used,” says Van Zyl. Syngenta Seedcare focuses on the part of crops most intimately in contact with soils, namely the roots.
Far from roots just taking from the soil, the relationship between the two is highly symbiotic. Healthy soils enable and support robust root systems and vice versa.
Plant roots help bind soil particles together which creates a stable soil structure, prevents soil erosion and top-soil loss, improves water infiltration and reduces compaction. Strong root systems also create channels in the soil that allow air, water and nutrients to penetrate more deeply.
While root systems extract nutrients from the soil, they also release organic compounds that attract beneficial microorganisms that enhance nutrient cycling and availability. By releasing compounds that feed beneficial soil microbes, roots contribute directly to the ability of soils to suppress harmful pathogens and decompose organic matter. The latter, in turn, improves carbon sequestration.
Roots furthermore release enzymes and compounds that can alter the chemical composition of the soil around them to enhance nutrient solubility and availability. In addition, certain plants release allelopathic compounds that suppress disease-causing organisms in the soil – a natural form of disease control that contributes to healthier soils.
Finally, healthy root systems serve as habitat and sustenance for soil organisms ranging from earthworms to mycorrhizal fungi, which contributes to ecosystem resilience.
The benefits of seed treatments
Syngenta’s root health drive focuses on the treatment of seed against fungal infections and nematodes to support the development of crop root systems that are robust and function optimally.
According to Professor Driekie Fourie, nematologist and Syngenta Seedcare team member, nematode pressure increases over time if populations are not managed. Her research also indicates that crop rotation systems currently used in South Africa are conducive to nematode build up. “A holistic management approach is critical, given that plant-parasitic nematodes often open the door to secondary fungal infections and these disease-nematode complexes worsen crop damage,” she says.
Van Zyl says that seed treatment is the first line of defence against plant-parasitic nematodes, fungal diseases and insect attacks, but it has to be supported by other management practices such as in-furrow applications and weed control.
“One of the biggest risks growers face is soilborne pathogens that infect seeds at the time of planting or seedlings as soon as they emerge,” notes Van Zyl. As a management tool, treating seed with fungicides significantly reduces the load of pathogenic fungi in the rhizosphere, or root microbiome, of crops without negatively affecting seed viability. Seed treatment furthermore ensures the chemical is placed exactly where it is needed, namely around the seed and the roots of the developing seedling, hence requiring less product and a smaller application area than in-furrow or foliar applications. Well-formulated products, such as Syngenta’s APRON Plus Beans, CRUISER White and CELESTE XL, not only protect seed and seedlings, but actively promote uniform emergence and healthy roots to support optimal yield. Seed treatments also target pests, allowing the beneficial species to do their good work, and producers can combine a fungicide with a nematicide in a seed treatment to prevent secondary fungal infections. “By controlling a key component of soilborne-disease complexes, namely pathogenic fungi, seed-applied fungicides support more sustainable and efficient farming practices that promote soil and plant health,” says Van Zyl.
In combination, healthy soils and healthy root systems result in better yields, bringing us closer to the goal of producing more food with less inputs. It is estimated that producers currently give away as much as 30% of their yields to pests and diseases. Better soil management can change this.
Much as food begins with soil, it also begins with roots. The call to action is therefore clear: producers across the world have to embrace their role and responsibility as the primary caregivers of agricultural soil in the interest of food security and climate change management alike.
