Agriculture is the backbone of the Ethiopian economy, and the agricultural sector is dominated by smallholder farming systems. The farming systems are facing constraints such as small land size, lack of resources, and increasing degradation of soil quality that hamper sustainable crop production and food security. The effects of climate change (e.g., frequent occurrence of extreme weather events) exacerbate these problems. Applying appropriate technologies like climate-smart agriculture (CSA) can help to resolve the constraints of smallholder farming systems. This paper provides a comprehensive overview regarding opportunities and challenges of traditional and newly developed CSA practices in Ethiopia, such as integrated soil fertility management, water harvesting, and agroforestry. These practices are commonly related to drought resilience, stability of crop yields, carbon sequestration, greenhouse gas mitigation, and higher household income. However, the adoption of the practices by smallholder farmers is often limited, mainly due to shortage of cropland, land tenure issues, lack of adequate knowledge about CSA, slow return on investments, and insufficient policy and implementation schemes. It is suggested that additional measures be developed and made available to help CSA practices become more prevalent in smallholder farming systems. The measures should include the utilization of degraded and marginal lands, improvement of the soil organic matter management, provision of capacity-building opportunities and financial support, as well as the development of specific policies for smallholder farming.

Combined application of organic and mineral fertilizers has been proposed as a measure for sustainable yield intensification and mitigation of greenhouse gas (GHG) emissions. However, fertilizer effects strongly depend on the soil type and still no precise information is available for Nitisols in Ethiopia. The study evaluated effects of different ratios of biowaste compost and mineral fertilizers (consisting of nitrogen (N), phosphorus (P), and sulphur (S)) on maize (Zea mays L. Bako-hybrid) yields in a two-year field trial. Soil samples from each treatment of the field trial were used to estimate emissions of nitrous oxide (N₂O), carbon dioxide (CO₂), methane (CH₄), and microbial activity in a 28-day incubation experiment with two moisture levels (40% and 75% water-filled pore space, WFPS). The application of fertilizers corresponded to a N supply of about 100 kg ha⁻¹, whereby the pure application of mineral fertilizers (100 min) was gradually replaced by compost. Maize yields were increased by 12 to 18% (p < 0.05) in the combined treatments of compost and mineral fertilizers compared to the 100 min treatment. The cumulative emissions of N₂O and CO₂ but not CH₄ were affected by the fertilizer treatments and soil moisture levels (p < 0.05). At 75% WFPS, the N₂O emissions in the 100 min treatment was with 16.3 g ha⁻¹ more than twice as high as the treatment with 100% compost (6.4 g ha⁻¹) and also considerably higher than in the 50% compost treatment (9.4 g ha⁻¹). The results suggest that a compost application accounting for 40 to 70% of the N supply in the fertilizer combinations can be suitable to increase maize yields as well as to mitigate GHG emissions from Nitisols in Southwestern Ethiopia.

The agricultural practice is a foundation for all global development. Increasing its production and productivity may affect the land capacity in the future if not managed sustainably. Sustainable agriculture could be one way to preserve land use potential. However, several obstacles impede its implementation, such as high reliance on external inputs to boost short-term output, lack of innovative technology in developing countries, and climate change impacts. Despite these obstacles, a variety of tackling options have been proposed, like decreasing the excessive usage of artificial fertilizer and relying on locally available organic materials as sources of plant nutrients. Improving small-scale irrigation practices by managing their negative environmental effects in small-scale agriculture could also enhance sustainable agriculture. This chapter briefly overviews sustainable agriculture, its components, and the potential and obstacles to achieving overall sustainability in both developed and developing countries.

The negative side effects of synthetic antimicrobial drugs as well as the evolution of drug-resistance in pathogenic microorganisms has raised the demand for immune system boosting nutrients. This chapter covers the recent research findings on immunity boosting in animals and humans by some selected plant nutrients, including extracts of garlic, ginger, green tea, echinacea, broccoli, and red pepper, and vitamins including vitamin C, D, and E. It has been shown that specific plant compounds that presented immune system fortifying activity can be isolated from the medicinal plants for further studies into their effectiveness. Some mechanisms behind the activities by which the specific plant nutrients and vitamins enhance the immune system function are described, although the detailed mechanisms require further study.

Proper fertilizer management and applications could effectively reduce global warming potential (GWP) and improving soil fertility under cereal production. However, the effect of soil fertilizer management practices on GWP and soil fertility is less understood in the agricultural soils of Ethiopia. The present study evaluated the effects of fertilizer application strategy on GWP, and soil fertility in a Nitisol. Both field and laboratory incubation experiments were conducted with the same treatments. Seven treatments (Cont: no input; 100 min: 100% mineral fertilizer, 80 min: 80% mineral fertilizer + 1.4 t ha⁻¹ compost; 60 min: 60% mineral fertilizer + 2.8 t ha⁻¹ compost; 50 min: 50% mineral fertilizer + 3.5 t ha⁻¹ compost; 30 min: 30% mineral fertilizer + 4.9 t ha⁻¹ compost, and 100 comp: 100% compost) with four replications were applied on maize crop (Zea mays L. Bako hybrid 661) for two consecutive growing seasons. The laboratory incubation experiment was also carried out with two moisture levels (40% and 75% of water-filled pore space) to simulate the seasonal rainfall pattern. GWP was calculated by summing up the quantified gas emissions of nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄). The laboratory result for GWP shown that soil fertilized with mineral fertilizer alone was significantly (p < 0.05) increased by 27–34% of the average GWP compared to combined fertilizer treatments in the soil at a moisture level of 75%. From the field experiment, most plant nutrients were significantly increased in combined fertilizer treatments compared to sole mineral fertilizer application. For example, carbon, calcium, magnesium and potassium were increased by 26.2–39.8%, 73.2–168.8%, 146.6–251.5% and 47–99% respectively in combined fertilizer compared to 100 min treatment. The study revealed that combining 30 or 50 kg N ha⁻¹ of mineral fertilizer with biowaste compost (4.9 or 3.5 t ha⁻¹) would be a suitable combination to mitigate the GWP and improve soil quality in smallholder farming systems, due to a slow release of N during decomposition into the soil compared to mineral fertilizer alone. However, to evaluate GWP under the field conditions, future investigations are recommended.