Estimating acid soil effects on selected cereal crop productivities in Ethiopia: Comparing economic cost-effectiveness of lime and fertilizer applications

Abstract

Acid soils are a major constraint to agricultural productivity in many parts of sub-Saharan Africa, including Ethiopia. Restoring soil pH to optimal ranges for agriculture can have a significant impact on yields, particularly for acid intolerant crops like wheat and barley. The application of agricultural lime is the standard corrective, although the large application requirements, lack of farmer awareness, and weak or non-existent lime supply chains make this a complex problem to address at scale. To date, no large-scale farmer trials of lime application have been undertaken in Ethiopia. This leaves open the question to local policy makers as to the economic benefits given the enormous capital and logistics investments required. To help address this we leverage existing spatial edaphic data and longitudinal crop surveys to simulate the productivity impact of varying lime and fertilizer applications. Our estimates find the impact of moving pH from 5.5 to 6.5, modeled as a lime soil remediation strategy, increases yields by 22% and 19% for wheat and barley, respectively. In addition, at lower pH levels our models indicate that commonly used nitrogen-based fertilizers are less cost-effective. For wheat in highly acidic soils, we find that fertilizers cost over two times as much as a single application of lime over a five-year period. The cost savings of the use of lime reaches as high as 121% of average one-year agricultural household income for wheat; with barley these savings are lower but still substantial at 24%. In general, we advocate for an integrated soil fertility management strategy that applies appropriate levels of fertilizer on pH balanced soil. If successful, Ethiopia’s acid soil reclamation could become a modest version of Brazil’s successful “cerrado miracle” and serve as an example for Africa.

Agricultural lime value chain efficiency for reducing soil acidity in Ethiopia

“…The specific objective is to explore the main actors, their roles, and functions as well as opportunities and challenges along the ag-lime value chain for the development of an efficient value chain. Together with other few studies ( Agegnehu et al., 2019 ; 2021 ; Warner et al., 2023 ), the study contributes to the development of acid soil reclamation strategy in Ethiopia that envision to bring impact like the Brazilian acid soil reclamation initiative in the Cerrado region ( Yamada, 2005 ). Given soil acidity is a challenge to other African countries ( AGRA, 2022 ), the study provides valuable information on the current value chain structure for enhanced food production by addressing the economics of soil health for improving farmers’ livelihoods in Ethiopia and other African countries.…”

“…According to farmers, soil acidity and fertility challenges were previously treated using local soil management practices such as fallowing cropland to improve the productivity of their land. However, the practice of fallowing cropland has limited prospect because of land scarcity and unsustainability to address the problem of soil acidity in the long-term ( Warner et al., 2023 ).…”

“…We also assessed the status of ag-lime awareness and utilization in the study areas. Insights from this ag-lime value chain analysis contribute to the ongoing broader efforts in guiding acid soil management investments in Africa ( AGRA, 2022 ; Agegnehu et al., 2021 ; Warner et al., 2023 ).…”

“…Abebe (2007) has reported that soil acidity is expanding in scope and magnitude across different regions of Ethiopia, particularly in the western parts of the country. Some studies have reported the severity of soil acidity, agricultural productivity challenges and ongoing initiatives to mitigate the problem in the country (e.g., Warner et al., 2016 ; 2023 ; Tamene et al., 2017 ; Amede et al., 2019 ; Agegnehu et al., 2019 ; 2021 ).…”

“…These include the cultivation of acid-tolerant plants, covering the surface with non-acidic soil, the use of organic fertilizers, and liming. Among these practices, liming and the application of organic fertilizers appear the best measures, because of their more persistent agronomic effects ( Chen et al., 2001 ; Desalegn et al., 2019 ; Warner et al., 2023 ). Ag-lime is a soil conditioner made from crushed limestone or dolomitic limestone with the primary active component of calcium carbonate.…”