European Journal of Sustainable Agroecosystems

Background: Soil degradation has already affected around one-third of the worldwide arable land using different factors, for example, erosion, compaction, salinization, acidification, and organic matter loss, which has a negative impact on food security, climate objectives, and ecosystem services (1,2). Integrated organic amendments that include compost, manure, vermicompost, biochar, and green manure/cover crops are widely accepted in use in publications, and still, there is no clear evidence that has been gathered about their effectiveness in countries from different disciplines.

Objectives of literature: The aim of this review is to analyze the existing peer-reviewed articles and institutional literature of 2015-2026 that focuses on the effectiveness of integrated organic amendments.

Sources of literature: The analysis and the search of the literature were conducted in such resources as Scopus, Web of Science, PubMed, as well as Google Scholar, which allowed finding 1665 publications, whereas only 77 among them corresponded to the criteria of inclusion according to the PRISMA style.

Key outcomes: The usage of organic amendments over a long term has been shown to enhance overall organic carbon content in the upper layers of soil by almost 24%. The use of a combination of biochar and compost has had a benefit of stimulating soil microbial biomass carbon development and giving the increase of more than 37% in the biomass carbon content if compared to the application of one of the amendments separately (3,4). The mixture of vermicomposting and compost mixtures consistently enhances soil aggregate stability, cation exchange capacity, and nutrient availability, while green manure/cover crops provide advantages through the increase of carbon input into the soil and increased nitrogen administration with lower costs in terms of input. However contradictory results appear in regard to optimum rates of application of amendments, amendment-specific characteristics across soil pH values, and certain unintended risks, such as heavy metal content, spreading of genes related to antibiotic resistance, or microplastic pollution originating from compost or manure sources.

Research gaps: The review highlights the lack of long-running (>5-year) multi-site field experiments, the lack of standardized soil health indicators to facilitate cross-study comparisons, the dearth of information on the tropical smallholder systems, as well as the inadequacy of contaminant risk trade-offs with the use of by-product amendments.

Conclusion: In terms of the restoration of soil health, the usage of integrated and context-specific organic amendment approaches rests on solid scientific foundations and can be successfully implemented in practical terms.