Pedological and agronomic assessment of salt-affected rice cultivation areas along a coastal gradient in the Zambezi Delta, Mozambique

Land degradation driven by climate change is increasingly manifested through soil salinity and sodicity in Eastern Africa, posing major threats to ecosystem functioning and agricultural productivity. In the region, including Mozambique, rice is a key staple crop cultivated on salt-affected soils. Salinity constraints are common to coastal rainfed and irrigated lowland rice production systems, with either direct seawater influence or irrigation with saline and/or sodic water resources. While the development of locally adapted salt-tolerant rice varieties is progressing, there is a major research deficit regarding the pedological variability and associated soil biogeochemical processes in the salt-affected rice production systems of Eastern Africa. Such knowledge is essential for designing sustainable soil and water-based salinity management strategies under increasing climate and land-use pressure. The recently initiated DFG-funded project “Disentangling the impact of salinity and sodicity on organic matter cycling in paddy soils of Tropical Eastern Africa” aims at addressing this knowledge gap. The focus lies on Mozambique’s principal rice production system in the lowlands of the Zambezi River Delta, where progressing seawater intrusion and agricultural encroachment on saline wetland ecosystems lead to pedological situations with varying degrees of salinity impact. We report preliminary results from an initial field survey conducted in June 2025 (onset of the dry season), which covered two sampling transects comprising contrasting rice cultivation environments defined by soil texture (heavy clay Fluvisols vs. interdunal sand/loamy sand Arenosols) with 3 field locations each, representing a gradient of soil salinity. In relation to this study design, we present data comprising soil profile descriptions, soil salinity parameters, along with organic matter and nutrient contents. Output from first selected farmer interviews complement the pedological assessment, providing insights into local perceptions of experienced environmental change and prevailing agronomic practices.