Increasing areas of agricultural land in high rainfall areas of Sub-Saharan Africa (SSA), where crop production used to be reliable, are affected by soil acidity. This review focuses on the extent, causes and effect of soil acidity on soil properties and crop yield and its management from the context of SSA. Studies showed that the detrimental effects of soil acidity can be mitigated through liming, integrated acid soil management and the use of acid-tolerant germplasms. Application of lime resulted in yield increments of 34–252% in wheat, barley and tef, 29–53% in faba bean and soybean, and 42–332% in potato in Ethiopia, 111–182% in maize in Kenya, and 45–103% in Mucuna in Nigeria under moderate to severe acid soil conditions. This was accompanied by a corresponding increase in soil pH up to 1.9 units and a decrease in exchangeable acidity and aluminum up to 2.1 cmol kg⁻¹. Use of acid-tolerant crop varieties such as maize expressing superior tolerance to Al toxicity resulted in a yield increase of 51% under low soil pH in Cameroon and Kenya. Overall, soil acidity covering ∼35% of SSA should be reclaimed with lime and integrated acid soil management interventions, which could significantly increase crop yield and enhance the resilience of the tropical agroecosystems. .

Land use change causes a remarkable change in soil properties. The nature of change depends on multiple factors such as soil type, type and intensity of land use, climate, and the like. It is essential to study and understand how these factors interact and affect soil properties. In this study, we investigated the variation in soil physicochemical properties across five common land use practices, i.e. enset system, farmland, and grazing-land (closed and open), and Eucalyptus woodlots practiced on originally same soil type and comparable topographic and climatic settings. A total of 105 soil samples from three depths of 0–15 cm, 15–30 cm, and 30–45 cm were collected and analyzed for selected soil physicochemical properties. The results showed significant differences between the land uses in soil physical and chemical properties. Enset system had higher pH, available phosphorus (P), exchangeable potassium (K⁺), soil organic carbon (SOC), and total nitrogen (TN) and their stocks than other land use types. Further, the widely accepted notion of the alleged effects of Eucalyptus tree on soil nutrient composition was not demonstrated in this study except its lower pH of (5.61) and soil moisture contents of (26.14%) than other land use types over 15–20 years old. SOC stocks showed a decreasing trend of enset system (127.36 Mg ha⁻¹) > closed grazing land (108.07 Mg ha⁻¹) > eucalyptus woodlot (92.55 Mg ha⁻¹) > open grazing-land (88.57 Mg ha⁻¹) > cereal farm (76.65 Mg ha⁻¹) at 0–45 cm soil depth, implying the potential of enset system for climate changes mitigation. TN was also measured in the same trend. Overall, some land use systems (e. g. enset agroforestry) improve the soil biophysical and chemical properties, while others such as cereal production degrade the soil. The low input continuous cultivation of cereal farm land coupled with its poor soil conservation measures in the area could be the major factors for the depletion of soil nutrient in cereal farming. Hence, future soil management strategies should be focused on mitigating the continuous loss of soil nutrients from the dominantly practiced cereal cropping system through the retention of crop residues, practice of crop rotation and scaling-up agro-forestry practice.

Integrated nutrient management, which primarily involves the combined application of organic and inorganic nutrient sources, is one of the simplest approaches to handle declining soil fertility challenges and increase crop productivity and production. Keeping in view this fact, a pot experiment was conducted to evaluate the effects of compost and inorganic nitrogen fertilizer and their mixture on soil properties, growth, and nitrogen uptake of maize on loam and clay textured soils at the Awada Agricultural Research Subcenter. Treatments comprised factorial combinations of five compost rates (0, 5, 10, 15, and 20t·ha⁻¹) and four rates of inorganic nitrogen fertilizer (0, 46, 92, and 138kg·N·ha⁻¹) laid out as a completely randomized design with three replications. Results showed that both the main and interaction effects of compost and mineral N fertilizer rates significantly affected the selected soil chemical properties and yield, and nitrogen concentration of maize. There were significant associations between plant parameters and soil nitrogen contents. The addition of 92kg·ha⁻¹·N+10t·ha⁻¹ compost and 46kg·ha⁻¹·N+10t·ha⁻¹ compost was the best treatments for loam and clay textured soils of the study areas, which improved shoot dry matter by 179.5 and 284.5, compared to the unfertilized pot, respectively. From the results of this experiment, we concluded that the integrated application of compost and mineral nitrogen fertilizer enhanced soil chemical properties and thus improved nitrogen uptake and sustainable production of maize in the study areas.

Land degradation and the associated soil acidity are critical challenge for crop production in Ethiopian highlands. Since liming is expensive, farmers have developed an alternative agroforestry system by integrating Acacia decurrens into their landscapes. The expansion rate of this system was assessed over the last three decades. The effects of the agroforestry system and charcoal-making kiln sites on soil properties were investigated for over five years compared to the adjacent croplands. Soil samples were collected from A. decurrens plantations, kiln sites, and adjacent croplands at 0–15 and 15–30 cm soil depths. In the last 30 years, the plantation and croplands increased by 8% and 17.5%, respectively, compared to the land-use system in 1993, mainly at the expense of grassland and abandoned land. The main incentive for expansion of A. decurrens plantations was farmers’ income generated from charcoal making. This intervention also improved soil properties with a significantly positive effect on soil pH, soil organic carbon (SOC), cation exchange capacity (CEC), and available Bray phosphorus (Bray-P) compared to the adjacent croplands. Results revealed that the SOC content in year 2 increased significantly (1.3–1.7 times) under A. decurrens plantation compared to adjacent crop fields. Moreover, soil pH increased by one unit on charcoal-making fields, which was equivalent to application of 4–5 t lime ha⁻¹, while SOC increased by ~ 10% on kiln sites compared to the control. Charcoal making kiln spots increased available soil phosphorus by 112% compared to the adjacent non-kiln sites. The Bray- P was strongly and significantly (P < 0.05) correlated (r = 0.75) with soil pH. We conclude that integrating A. decurrens-based agroforestry practices would improve livelihoods by restoring degraded lands, improving income generation and carbon sequestration.