Umamaheswari P. and B.M. Gore
Abstract
Alkaline and sodic soils represent a major constraint to sustainable agriculture, particularly in arid and semi-arid regions such as India. These soils are characterized by high pH (>8.2), elevated exchangeable sodium percentage, poor structure, restricted water movement, and limited nutrient availability, resulting in low crop productivity and land degradation. Conventional reclamation strategies, notably gypsum application, are effective in replacing exchangeable sodium but are often costly and slow to restore biological soil functions. Consequently, biological approaches have gained increasing attention, with earthworms-especially Eisenia fetida-emerging as potential ecosystem engineers in soil reclamation. This narrative review synthesizes peer-reviewed literature published between 2014 and 2024 to critically evaluate the role of E. fetida in alkaline soil restoration. Emphasis is placed on mechanistic pathways, including organic matter decomposition, vermicast production, improvement of soil structure, stimulation of microbial activity, nutrient cycling, and interactions with organic and chemical amendments. The review also considers the bioaccumulation capacity of E. fetida and its relevance for contaminant immobilization in degraded soils. Evidence indicates that vermicompost produced by E. fetida improves soil pH regulation, cation exchange capacity, organic carbon content, C/N ratio, and the availability of essential nutrients such as nitrogen, phosphorus, and potassium in alkaline soils. However, species-specific constraints, contradictory findings, and challenges related to scalability and field-level application are also highlighted. Overall, E. fetida demonstrates significant but context-dependent potential for alkaline soil reclamation, particularly when integrated with organic amendments and gypsum. Key knowledge gaps and future research priorities are identified to support the development of sustainable and biologically driven soil restoration strategies.