The Marginal Soils of Africa

The popular perception of rangeland and the management, in Sub-Saharan Africa, is mostly negative. The vast areas are seen as a problem without a solution. The common focus on the negative is overgrazing, undernourished livestock and desertification. With the world population increasing, especially in Africa, food production is a priority. With Africa having rangelands accounting for at least 65% of the surface area, this constitutes a major area for animal production. The chapter aims to alleviate the negative perceptions by adopting one of the grazing strategies, firstly by defining different grazing strategies. By the adoption of a grazing strategy the degraded rangeland can be reversed to good quality rangeland.

The use of marginal soils is fundamentally important in the implementation of the biofuel strategy in South Africa. However, the anticipated increase in production, particularly in the former homelands may present several challenges. For instance marginal soils are highly susceptible to soil degradation. Therefore, benefits achieved through carbon sequestration are erased by the negative effects of intensification of production and land use change. Moreover, annual biofuel crops may deplete soil organic matter (SOM), cause soil erosion, nutrient depletion and soil pollution through associated direct and indirect land use change. Consequently, the application of conservation agriculture (CA) was identified as a potential sustainable production system for producing bioenergy sweet sorghum in South Africa. Several studies conducted in South Africa attest to the benefits of CA in improving soil fertility and crop productivity. This chapter seeks to highlight the potential of CA to sustain sweet sorghum production on marginal soils. The work summarizes main finding on the effect of tillage, crop rotation and residue management on physical and chemical soil properties in a study done in Eastern Cape marginal lands, South Africa, in a sweet sorghum production system. The highlighted findings show that CA significantly improved the major aggregate binding agents. Mean weight diameter (MWD) and selected binding agents (soil organic carbon (SOC) and glomalin-related soil proteins (GRSP)) were significantly influenced enhance by NT compared to CT. NT also increased Bulk density and penetrometer resistance while all the treatments did not influence infiltration rate. NT and residue management at 30% increased soil nutrient availability. In addition, NT+ 30% residue retention interaction increased NH₄⁺-N and potassium (K) availability. The application of NT + 30% treatment combination was identified as a potentially sustainable production system that can enhance soil quality indices in marginal soils of Eastern Cape under sweet sorghum as a biofuel feedstock.

The global demand increase for animal-source foods allows smallholder livestock farmers to improve food and nutrition security and their livelihoods. However, livestock production significantly contributes to global change with several negative environmental effects, including greenhouse gas emissions, high water consumption, acidification, air pollution, land degradation, and biodiversity loss. Therefore, the sustainable intensification of livestock production systems, such as improving the quality of feed, range and grazing land rehabilitation, and introduction of improved forages that deliver economic and ecosystem services without compromising the future integrity, health, and welfare of the environment and humans as a whole has become a critical global research priority. This study reviews the improved sustainable approaches to animal feed production to increase food security and reduce greenhouse gas emission forces in Africa. Therefore, in the transition to sustainable livestock production, there is a need for assessments related to appropriate strategies for sustainable intensification of livestock, such as improving the quality of feed, introducing improved forages, and improving herd genetics can reduce greenhouse gas emissions while strengthening livestock productivity; nutrition, and feeding system.

Soil fertility degradation is occurring in almost all terrestrial biomes and agroecologies in southern African (SA) countries. However, its impact is especially severe on the livelihoods of the poor, who are heavily dependent on farming, and this has further pushed the farmers to cultivate on marginal lands. All three (biological, chemical and physical) forms of land degradation are being experienced on farmers’ fields. Some of the causes of soil fertility degradation are overgrazing, deforestation, climate change and unsustainable farming practices. Most studies conducted in SA showed that agroforestry systems (AFS) can replenish degraded lands through improvement of soil fauna, soil organic matter, nitrogen and carbon content, aggregate stability, infiltration and lowering bulk density and runoff. Pigeonpea improved fallows have been shown to double maize yields compared to traditional farming system (continuous maize without fertiliser). Agroforestry systems could enhance the resilience of agricultural production to current climate variability. It can be a long-term solution to this variability through utilisation of legume trees for intensification and diversification as well as buffering of farming systems. For scaling AFS in SA, there is need for policy interventions in each country. This will help in solving the challenges of soil fertility degradation and lessen the burden of buying expensive chemical fertilisers by vulnerable smallholder farmers.

Food security and environmental conservation are crucial worldwide issues, especially given climate change’s uncertainty. The food system still deals with increased food production demand and dietary changes driven by population expansion and increasing environmental concerns. Climate change has far-reaching implications for global food security, and its effects on soil fertility, water scarcity, severe temperatures, carbon sequestration, microbial activity, and food production have already had a considerable impact on agricultural productivity worldwide. Significant modifications in food production, distribution, and consumption patterns are required to adapt to climate change and ensure global food security. As a result, excess food must come from marginal lands unsuitable for growing key staple crops under the worst-case climate change scenario. Underutilized neglected crops are promising for improving food and nutritional security because of their high nutritional profile and better tolerance to numerous abiotic stressors. This book chapter thoroughly discusses climate change and its effects on agricultural products, food and nutrition insecurity, and the necessity for expanding people to adapt to shifting climatic circumstances. Identify the critical success factors and issues that must be addressed to attain extensive adoption of climate change resilient crops using underutilized, neglected crops to alleviate food poverty and ensure appropriate nutrition on marginal lands.

Conservation agriculture (CA) holds significant potential for enhancing crop productivity and soil health in Sub-Saharan Africa (SSA), a region facing food insecurity, poverty and climate change challenges. This chapter reviews the adoption and effectiveness of CA practices within SSA’s smallholder farming systems, considering their potential to improve soil quality and increase crop yields on marginal lands. Despite the proven benefits of CA, its adoption remains low among smallholder farmers, mainly due to complex socioeconomic and biophysical factors that affect their ability to implement the three core CA principles: minimum soil disturbance, maintaining soil cover, and crop diversification. Local research initiatives have provided valuable insights into the challenges, benefits, and adaptations necessary for successful CA implementation in SSA. These studies have assessed a range of parameters, including soil chemical, physical, and biological properties, greenhouse gas emissions, crop yield, and socio-economic implications. This chapter emphasises the potential of CA to enhance crop and soil productivity, contributing to sustainable farming practices on marginal lands in SSA. The ability of CA to improve soil organic matter, soil structure, water infiltration, nutrient cycling, and pest management is discussed. However, challenges such as limited awareness, access to resources, risk aversion, and cultural factors hinder widespread adoption. The chapter concludes with strategies to scale up CA adoption, including policy support, knowledge dissemination through extension services, and private-public partnerships. By leveraging local research and engaging stakeholders, SSA can promote conservation agriculture as a means to achieve sustainable agricultural development, food security, and improved livelihoods in marginal lands.

This book chapter discusses approaches to promoting low-input agricultural practices to improve marginal lands for sustainable crop production and food security. Agricultural production in sub-Saharan Africa is lower than in different parts of the world, attributed to many factors such as climatic conditions, soil quality, pests, and diseases. The projected increase in population in the sub-Saharan countries is estimated to reach 4.3 billion by 2100, which has made it urgent to resort to strategies to meet the growing demand and avert food insecurity. The promotion and adoption of agricultural practices presented in this chapter delineate the contribution to marginal lands. The practices include conservation agriculture, crop rotation, and cover cropping, intended to integrate and facilitate improved nutrient uptake through different mechanisms for marginal soils. This chapter highlights the benefits of sustainable agricultural practices, including the potential for improved crop performance, soil health improvement through cover cropping and stimulating nutrient uptake, and improved crop productivity.

Over the past decades, cumulative loss of productivity of cropland has been estimated at about 13% at a global scale but this could be even more at a subnational or national scale. In Zimbabwe, the largest (>60%) area is affected by various forms of soil degradation and the communal areas are the worst affected with an annual soil loss that averages 3.3 t ha^–1. The soil degradation from farmlands is reflected by the reduction of crop production potential, lower surface water quality and damaged drainage networks. The decline in soil characteristics in Zimbabwe is caused by its inappropriate use, typically for agricultural production in the communal areas. Loss in soil quality is a major threat to “soil security,” and is ubiquitous across the globe in its various forms and at varying magnitudes, depending on the specific demands of people and the inexorably increasing pressures on land. Soil degradation is one of the most important threats facing mankind which not only weakens the productive capability of an ecosystem but also affects overall climate. Soil degradation reduces food security especially at the subnational and national levels in the developing countries as it decreases land’s productive capacity. Therefore, efforts should aim at rehabilitating the degraded soils in order to increase crop productivity. However, the causes and mitigation strategies are unique and depend on specific land use and prevailing climatic conditions. It is prudent to address the issue of soil degradation starting at lower levels like a farm which will then feed into the national grid of soil degradation. Most soils in the communal areas of Zimbabwe are heavily degraded as they have lost their physical, chemical or biological qualities that underpin the web of life, hence low crop productivity. This exposes the communal population to acute food shortage. If no corrective measures are taken, this trend is projected to continue at alarming rates in the future. Therefore, this chapter aims at reviewing possible strategies that can be used to regain the high soil quality status in the communal farmlands of Zimbabwe.

Land degradation caused by factors such as climate change and pollution is among the prominent environmental challenges currently confronting the world; this has resulted in poor soil quality leading to loss of soil fertility as well as loss of biodiversity. In order to address the adverse implications of climate change and improve food productivity and ecosystem function, it is necessary to minimize land degradation and rehabilitate marginal or degraded lands. This can be achieved through monitoring soil quality, including identifying soil health indicators to detect changes caused by both natural processes and human activities such as changes in land use, pesticide application, and fertilizer use. Monitoring of soil quality can provide valuable information on soil health and ecosystem functioning. Despite the importance of soil monitoring indicators, certain limitations have been observed. In recent times, biotechnological strategies for monitoring soil quality have gained increasing attention in evaluating the soil’s chemical, physical, and biological features as it has allowed for a more efficient and accurate soil quality analysis. Current developments in biotechnology have necessitated the need to explore the prospect of incorporating biotechnological approaches in the monitoring of soil quality. This includes soil enzymes, microbial biomass, diversity, and activities, nano biosensors, metagenomics, etc. The application of biotechnological approaches as sustainable means of monitoring soil quality for possible reclamation of marginal lands forms the basis of this chapter.

The quality of agricultural soils contributes to the amount of food produced globally for the entire world’s population. However, there are several environmental restrictions that often result in reduced agricultural output. The constraints include abiotic and biotic stresses and can affect both agricultural and marginal soils. Keeping in mind that crops require different nutrients for development, nanofertilizers (or nanonutrients) have emerged as potential tools for agricultural sustainability, particularly for the marginal environments that experience both biotic and abiotic challenges. Nanofertilizers have the potential to significantly increase plant production, both qualitatively and quantitatively. Due to their minute size, these fertilizers are the ideal solution to overcome the environmental and health issues that traditional fertilizers may cause because they are more easily absorbed by the plant through targeted distribution and are less likely to leach into the environment. Caution should however be placed on the effect these nanofertilizers, as known antibacterial agents, can have on soil ecosystems. Therefore, this chapter elucidates the role of nanofertilizers as micronutrients for crop production under stressed conditions that might be experienced on marginal lands.

Sustainable wheat production is challenged by rapid changes in climatic conditions and decreasing water security. Moreover, the ever-escalating global population puts further strain on agricultural systems, particularly on wheat, which is one of the main staple foods in the world. The demand for wheat is emphasized in Africa, where the population is rapidly increasing. Whilst wheat is cultivated in Africa, a large portion of the wheat consumed is imported. Increased wheat cultivation in Africa will improve food security and the African economy by reducing the need for wheat importation. However, for this to be achieved it is essential to expand wheat cultivation into marginal lands to ensure that adequate yield is generated, as the dwindling arable lands alone cannot support sufficient wheat cultivation to meet the demands of the growing population. Marginal lands are challenged by biotic and abiotic stressors. A key element to optimize cultivation of wheat on such lands is the introduction of resilient cultivars that can withstand and thrive under the harsh conditions imposed. Targeted breeding of wheat cultivars that can adapt to specific marginal environments are proposed to improve wheat yield in Africa. Moreover, it is proposed that landraces be considered as a treasure trove of traits of importance for wheat cultivation in sub-optimal agricultural lands. This chapter provides an overview of the current state of wheat cultivation in Africa with the prospect of expanding cultivation to marginal lands. Biotic and abiotic stresses imposed on marginal lands are discussed. Breeding strategies and beneficial traits that may be targeted for breeding are also outlined.

Improving marginal lands to overcome challenges in land use, such as land abandonment prevention and biodiversity conservation, has garnered increasing attention from policymakers and scientists. In the context of rehabilitating marginal lands, the consideration of edaphic arthropods becomes paramount due to their multifaceted roles within the soil. The productivity of marginal lands is influenced by a complex interplay of various interconnected factors, including nutrient balance, nutrient release capacity, soil acidity, organic matter content, soil structure, and water retention. The long-term functionality of these soil processes in agricultural lands is heavily reliant on the activities of arthropods inhabiting the soil environment. Soil-dwelling arthropods play a pivotal role in ecosystem functioning, notably in nutrient cycling, facilitating plant nutrient uptake, and regulating pest populations, which ultimately impacts plant health, physiology, and overall performance. Recognizing the ecological importance of soil arthropod biodiversity is critical in the development of a future sustainable agricultural strategy. The potential for better agricultural production on marginal lands can be achieved by incorporating their contributions into land management practices that maintain ecological balance and sustainability.

Soil quality restoration and maintenance are fundamental to achieving food security for the world’s growing population. Despite the importance of soil quality in ensuring food security, most of the lands in Africa and the world at large are predominantly marginal soils. Their ubiquitousness makes them vital in efforts to bring about food security, despite being characterised by poor soil properties which threaten sustainable food production. Arbuscular mycorrhizal fungi (AMF) play an important role in enhancing soil quality and function. The collected literature shows that AMFs can enhance soil properties and crop yields even in marginal soils with soil organic carbon of less than 1%. The extent to which AMFs can enhance soil quality is, however, influenced by the soil type. The data also show that the application of a no-till approach, crop residue retention, crop rotation and organic amendments can improve AMF abundance and diversity even in marginal soils. The conclusion reached, is that AMF have the potential to enhance soil quality and function, thus leading to increased food security. Admittedly, local studies on the best practices to enhance soil AMFs are still needed in Africa, especially under smallholder conditions.

Soilless recirculating hydroponic systems (those in which the nutrient solution is continuously recirculated and reused into the system) are well known for their potential to maximize crop production with minimum inputs of fertilizer and water, resulting in improved yields and quality of fresh produce, as well as increased farmer’s profitability and environmental preservation. The most implemented recirculating hydroponic systems in South Africa include the gravel and nutrient film, ebb-and-flow, and deep-water-culture techniques. Appropriate management and maintenance of these systems are crucial for increased crop productivity and water use efficiency. This is particularly relevant in South Africa for being a food-insecure and water-scarce country. This chapter highlights important production factors in recirculating hydroponics, typical crop yields, and water use efficiency obtained under South African conditions while emphasizing potential focus areas for research to improve the profitability and sustainability of crop production in soilless recirculating hydroponic systems.

Marginal soils have a reduced capacity for crop production due to physical and chemical limitations. These marginal soils, which are highly susceptible to degradation are dominant in sub-Saharan Africa (SSA). The high demand for agricultural land makes these soils valuable for agriculture within the smallholder sector. However, for them to be used profitably and to contribute to food security, they need to be revitalised through various rehabilitation processes. Black soldier fly frass (BSFF), a by-product of black soldier fly larvae is fast gaining recognition as a potential sustainable organic material for the resuscitation of marginal soils. BSFF is used to make an organic fertiliser known as black soldier fly frass fertiliser (BSFFF), which is rich in nutrients such as nitrogen (N), phosphorous (P), potassium (K) and a host of beneficial microbes. The fertiliser is also high in organic matter, which makes it attractive for soil structural improvement. This chapter highlights the potential of BSFFF in revitalising marginal soils, and in-turn improving crop productivity and food security in SSA. Preliminary findings from across SSA have shown improvement in soil physiochemical properties and crop growth and yield following application of frass fertiliser. However, several drawbacks have been identified such as prohibitive costs of equipment and knowledge gaps since this is still a new technology. This challenges could be addressed through collaborative research efforts, policy support and increased awareness campaign to inform farmers of the potential benefits of BSFFF. Since most of the available research came largely from laboratory and glasshouse experiments, there is need for long term field experiments on marginal soil across SSA to establish the real world effects of frass fertiliser. It also pertinent to study the potential integration of BSFFF into existing climate smart agriculture technologies such as conservation agriculture as well as the possibility of combining BSFFF with other organic amendments such vermicomposting and biochar.

Soil degradation is a common challenge impacting crop production in Sub Saharan African (SSA). One of the major causes is little or no use of either organic or inorganic soil fertility amendments due to cost and availability issues leading to low crop production. Vermicompost can play an important role in improving soil health especially of degraded soils. This chapter explores the benefits of vermicompost use in managing degraded soils. Due to its organic nature, vermicompost can improve soil biological, chemical and physical properties for increased soil health and crop productivity. Vermicompost contain earthworm castings which are rich in nutrients such as nitrogen, phosphorus, and potassium in available form which significantly improve fertility of degraded soils. Vermicompost is high in organic matter which increases the diversity and abundance of soil micro and macrofauna. Additionally, vermicompost contains micronutrients which many inorganic fertilizers do not have hence is very useful in improving crop production. Vermicompost has also been found to improve soil porosity, aeration, structure, aggregation and soil water retention However, despite its ability to improve soil health, vermicompost still remains under-utilized especially in SSA where most communal soils are severely degraded. Given the high costs and at times untimely availability of inorganic fertilizers, vermicompost can be a sustainable alternative source of nutrients for improving soil fertility and increased crop production. Therefore, there is need for promotion of vermicompost use especially among communal farmers in SSA for improved soil health and crop productivity.

This chapter examines the pressing problem of African soil degradation and looks at reclamation options to restore marginal soils to ensure sustainable food production. These soils severely hamper the productivity of the region’s agriculture, food security and the health of its environment, frequently characterised by low fertility, a propensity for erosion, and limited water retention. Beginning with explaining the characteristics and causes of soil deterioration in African marginal soils, the chapter start by emphasising the urgent need for efficient reclamation solutions. It offers an in-depth analysis of reclamation technologies, classifying them into physical, chemical, and biological approaches. Handling the various soil restrictions requires an integrated strategy integrating several technologies. Case studies demonstrate the transformative potential of reclamation efforts by showcasing real-world successes. While highlighting the significance of community involvement and context-specific solutions, these case studies also uncover crucial success elements like capacity building and adaptive management techniques. The chapter examines methodology and assessment indicators. Evaluating the effectiveness of reclamation technology is essential. Long-term monitoring and adaptive management are necessary to assess progress, address problems, and improve strategies. Addressing the various soil restrictions should emphasise using an integrated strategy that integrates several technologies.

Rain-fed crop production by smallholder farmers in arid and semi-arid regions of Sub-Saharan Africa (SSA) is highly vulnerable to the effects of climate change. Marginal soil fertility and environmental adversities caused by climate change such as global warming, erratic rainfall pattern, extended dry spell, drought and declining soil fertility negatively affect crop productivity resulting in food insecurity. Rainwater harvesting technologies (RWHT) offer potential solution to crop resilience under moisture stress, which is frequently encountered by farmers under dry-land crop production in the semi-arid regions of SSA. However, the success of these water harvesting technologies and their long-term sustainability in crop production on marginalised soils is missing. The objective of this book chapter is to review different RWHT, their potential to transform and provide sustainable dry-land crop production, food security and generate income for smallholder farmers in marginalised semi-arid soils in the southern region.