Soil physicochemical characterization and suitability assessment for the coastal mangrove swamp rice production system in Guinea-Bissau

Abstract

The mangrove swamp rice (MSR) agroecologies are widely acknowledged as crucial for rice production in West Africa, particularly in Guinea-Bissau. However, the optimal functionality of soil–water dynamics for rice cultivation, is constrained by poor soil fertility, waterlogging condition, or high soil salinity. Climatic variability, including unpredictable rainfall, droughts, and extreme weather, exacerbates these issues. Additionally, economic and social factors, including limited access to resources, labor shortages and market instability, further hinder farmerś ability to adapt, increasing mangrove swamp rice production (MSRP) vulnerability, threatening yields and food security. Soil characterization and suitability assessment serve as the foundational steps to investigate, describe, and identify constraints that small-scale farmers face daily in their production activities. In this study, soil profiles and nursery topsoils were described, sampled, and analyzed between 2022 and 2023 in three coastal areas and four villages of Guinea-Bissau, serving as study cases: Elalab (North), Malafu and Enchugal (Center), and Cafine (South). The physicochemical properties of soil were analyzed in the laboratory, and then subsequently utilized for classification and suitability assessment. Results revealed that soil profiles in the northern region exhibit structural limitations and low nutrient levels [nitrogen(N), phosphorus(P), potassium(K)] due to high sodicity concentration (> 5 cmol (+) kg⁻¹), which consequently limit rice growth and yield. Conversely, soils in the southern and central regions show significant acidification and salinization, induced by reduction conditions and jarosite formation. Shallow nursery upland soils (Oio region, center) exhibit low nutrient content and water retention capacity, restricting seedling root growth. In conclusion, the establishment of enduring and adaptable strategies for innovative soil management practices in MSRP demands bridging farmers’ traditional agricultural knowledge and practices with scientific insights. Innovations will be produced through the systematic collaboration between experts, scientists and farmers, who will share observations, experiences and knowledge to foster the development of nature-based solutions.