Restoring Soil Organic Matter Content for Managing Soil Health in Africa’s Agroecoregions

Soil health refers to its capacity to sustain multiple ecosystem services for human wellbeing and nature conservancy through coupled cycling of carbon with other elements. Among numerous key indicators, soil organic matter (SOM) content is widely considered the heart of soil health. However, most cropland soils of Africa have been subject to anthropogenic climate change, in which soil has been a source of greenhouse gases since the dawn of settled agriculture, and thus leading to reduction in SOM content. The optimum level of SOM content may range from 2-4% for soils of the temperate climate compared with 1-2% in those of tropical regions. However, soils of most agro-ecosystems in Africa have been subjected to land misuse and soil mismanagement, and thus are, severely depleted of their SOM content because of extractive farming practices. These systems can lead to a negative nutrient budget and thus mining of nutrients with the attendant severe depletion of SOM content in the root zone to often as low as 0.25% or less. Thus, agronomic productivity, use-efficiency of inputs (e.g., fertilizers, irrigation, energy-based farm operations) and the nutritional quality of food produced is low. The way food is produced and consumed in sub-Saharan Africa (SSA) can adversely affect health of soil, plants, animals, people, ecosystems, and the planetary processes. Extractive farming can disrupt soil-based “One Health” concept. The widely observed trend of a downward spiral aggravated by soil degradation also signifies the importance of inter-connectivity and other laws of ecology. It is thus pertinent that soil health of agro-ecosystems of SSA are restored by re-carbonization of soils and landscape. The term carbon sequestration implies transfer of atmospheric CO2 into long-lived soil/tree C pools so that it is not readily re-emitted into the atmosphere. The wide range of options of sequestration of atmospheric CO2 include oceanic, geological, chemical, and terrestrial. The goal of creating a positive soil/ecosystem C budget can be met by adopting practices in which input of C into the soil exceeds the losses by decomposition, erosion, and leaching. Wide range of agronomic management practices, specifically focused on the strategy of producing more from less, include regenerative agriculture, agro-ecology, and of replenishing plant nutrients as CNPK (rather than NPK). Specific climate-resilient practices comprise of a system-based conservation agriculture, cover cropping, complex farming systems, integrated soil fertility management and integration of crops with trees and livestock. Adoption of conservation-effective systems can be promoted through payments to farmers for strengthening of ecosystem services such as sequestering C in land-based sinks, improving quality and renewability of water, strengthening below-and-above-ground biodiversity, etc. Such pro-agriculture and pro-farmer policies can be advanced through adoption of a “Soil Health Act” at local, state, national, continental and global scale.