Soil health: our health, our wealth

Soil, the loose surface material that covers most land, is intuitively embedded in our minds. Although we may not always consciously consider its role in our day-to-day lives, we have an intrinsic awareness of the importance of soil – it is the poetic connection to country, to home.

More functionally, soil is a living, life-giving resource; a fundamental terrestrial asset, which, along with sunlight and water, provides the basis for all life. It is the Earth’s skin, providing a protective covering; an environmental buffer that resists erosion, prevents floods and regulates temperature. It is the “switching yard” for the global cycles of carbon, water and nutrients like nitrogen, phosphorus and many others, which are stocked, transformed and cycled through it. Soil is key to the survival of people and animals, a foundation for human structures and habitats for various fauna such as ants, mites, beetles, termites, nematodes and earthworms.

Soil is the physical anchor for most plants, and the support system for crop production. It is a treasure trove of beneficial microorganisms like bacteria, fungi and archaea, collectively known as the soil microbiome. The rich tapestry of soil biodiversity has highly complex and elegant interactions that facilitate biological equilibrium. For example, they help plants to tolerate unfavourable conditions and toxic contaminants, and to suppress pests, pathogens and diseases.

“To forget how to dig the earth and to tend the soil is to forget ourselves.” – Mahatma Gandhi

SOIL HEALTH IN AFRICA

Soil health is its capacity to sustain biological productivity, maintain environmental quality and promote plant and animal health. Indicators of soil health are a set of chemical, physical and biological characteristics. They encompass levels of nutrient cycling; soil fertility including the availability of minerals such as nitrogen, phosphorus and potassium among others; organic matter quantity and quality including carbon-nitrogen ratio, microbial biomass carbon, enzymes and decomposition. Other measures are the soil’s physical stability; the ability to resist disintegration due to tillage, or erosive forces such as water or wind; soil loss and soil depth; water holding capacity and infiltration. Soil health is also indicated by mineral toxicity levels such as salinity, sodicity and aluminium toxicity, as well as the presence of heavy metals and pesticides.

“The nation that destroys its soil, destroys itself,” thus lamented Franklin D. Roosevelt, President of the United States of America (1933 – 1945), when reflecting on the Dust Bowl era.

A 2022 report by the Food and Agriculture Organization of the United Nations (FAO), notes that 40 per cent of the soils in Africa have naturally low soil fertility, compounded by further degradation through processes such as nutrient mining. An earlier study by the Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA, 2020), found that in sub-Saharan Africa, 65 per cent of arable land has deteriorated due to erosion-induced losses of topsoil and soil nutrients, chemical-intensive agriculture and poor soil management.

Globally, there are calls for measures for soil protection, as well as the restoration and rehabilitation of degraded ecosystems, for sustainable crop production and food security. This plea is key to the United Nations Food Systems Summit, held in 2021. Also, the Sustainable Development Goal (SDG) 3, emphasises the interconnection between soils, good health and well-being. In 2020, the African Union commenced an ambitious continental effort to stimulate the reversal of soil degradation in the continent.

ONE HEALTH FOR SOIL HEALTH

icipe takes a nature-positive, One Health, systems-approach to soil health, by promoting regenerative agricultural practices that protect soils from harmful chemicals and synthetic products. Our strategies also help to rejuvenate and recover soil organic matter and to boost soil fertility under changing climate and habitats. These actions contribute to the production of safe, nutrient-rich foods for people and fodder for animals.

In addition, we harness beneficial organisms in the soil for the biological control of crop pests and disease vectors of people and animals. We also generate knowledge on soil ecosystems in relation to insect-transmitted pathogens, as well as tools to measure soil health. By supporting sustainable livestock production, icipe helps to reduce the impact of greenhouse emissions while exploiting the potential of livestock in soil rejuvenation.

“icipe takes a nature-positive, One Health, systems approach to soil health, thus contributing to its restoration and rehabilitation; sustainable crop production and food security; and good health and well-being of the environment, people and animals,” said Dr Segenet Kelemu, Former Director General, icipe.

EXAMPLES OF icipe SOIL HEALTH RESEARCH

Integrated pest management

icipe harnesses the synergies in plant-insect-soil interactions to develop environmentally friendly, sustainable, affordable and accessible integrated pest management (IPM) options for pests of vegetables, fruits and staples such as cereals, tubers and bananas. Our portfolio includes biological control of pests using other organisms such as predators and parasitoids; biopesticides and botanicals; naturally derived attractants and repellents; and cultural practices like intercropping. These strategies reduce the misuse and overuse of chemical and synthetic products. They demonstrate that it is possible to control crop pests and to increase yield without harming the Earth.

Push-pull technology

The push-pull technology involves intercropping cereals with legumes, for instance, Desmodium species, and planting fodder grass, such as Brachiaria, around the intercrop to control stemborers, the parasitic Striga weed and the fall armyworm. Our studies show that the technology’s companion crops, both perennial plants, restore soil function and fertility, and increase soil organic carbon and nitrogen, while also improving the availability of phosphorus to plants and reversing soil degradation. The push-pull technology provides about 70 per cent soil surface cover. Through its biomass, the technology recycles five times more nitrogen, phosphorus and potassium than maize monocrops. In addition, the technology enriches the diversity of soil microbiome community that is associated with important ecological services, while reducing those related to plant diseases, mycotoxin production and removal of nitrogen from the soil.

Biopesticides

Over the years, icipe has identified a range of strains from the soil-borne, insect- infecting Metarhizium anisopliae fungus. We have used these strains to develop a variety of powerful biopesticides, which have been commercialised by our private sector partners. They include: ICIPE 69 (Campaign), for fruit fly, thrips and mealybugs; and ICIPE 62 (Supreme), for aphids. Several soil-derived, icipe biopesticides, which are effective against the tomato leafminer, Phthorimaea absoluta, and the fall armyworm, are in the process of registration.

Nematode control

Plant parasitic nematodes, soil-dwelling worms, are a major, yet neglected challenge, for crop production in Africa. icipe’s groundbreaking chemical ecology research has opened up avenues for their control. In addition, together with IITA, we have generated new knowledge on the distribution and damage of various nematodes in Africa; developed diagnostic capabilities to identify and quantify them; and boosted capacity and awareness for their management. We are also testing control tools including dead-end trap crops, resistant crop varieties, and biological control products such as the soil-dwelling trichoderma fungi and garlic extract formulations. Further, we are exploring the use of beneficial nematodes, especially the entomopathogenic species, in the control of insect pests.

Banana fibre paper technology

Based on previous research by icipe and IITA, we are working with private sector partners to commercialise an evolutionary banana fibre paper technology to manage nematodes and other soil-dwelling pests. While we know that the technology improves the delivery and effectiveness of nematicides, we aim to establish its safety to soil health and the microbial environment. In partnership with James Hutton Institute, UK, we are conducting a series of tests including evaluations on the use of microBIOMETER, a low-cost test that enables quick soil health assessments, and molecular barcoding of the soil microbial environment. his research creates a basis for microbiome soil health assessments.

Insects for food, feed and other uses

icipe’s pioneering research has demonstrated the potential of various farmed insects such as black soldier flies, as effective recyclers of organic wastes into green frass fertilisers that contain good concentrations of nitrogen, phosphorus, potassium and soil micronutrients. We have illustrated that these products improve soil fertility, contribute to soil carbon sequestration, and enhance the soil water retention capacity and organic matter. In addition, we have established that chitin and chitosan, which naturally occur in the skeletons of insects, control various plant pests including soil-dwelling pests. Moreover, insect farming takes the pressure off scant land resources, thus circumventing a range of challenges associated with traditional agricultural activities including soil degradation. Further, insect-based feeds boost poultry farming, thus increasing the availability of manure.

“To be a successful farmer one must first know the nature of the soil.” - Xenophon, Ancient greek philosopher and historian, student of Socrates, Circa 430 - 354 BC

“The Nation that Destroys its Soil…” a Letter from the President (link: https://soilcarboncoalition.org/learning/FDR-INVESTIGATION.pdf)

The Dust Bowl was a period of severe dust storms during a drought in the 1930s in regions of the United States. High winds and choking dust swept across the regions, killing people and livestock and causing crop failure (Source: https://soilcarboncoalition.org/learning/FDR-INVESTIGATION.pdf)