Biochar-soil-plant interfaces: a systematic review of the crop performance in tropical climate

Biochar is increasingly being assessed as a promising solution to address the challenges faced by tropical soils, as it can help mitigate land degradation, replenish nutrients, and enhance soil structure, increasing fertility and promoting the development of crops. This paper provides a systematic literature review towards an evaluation of the current knowledge on the influence of biochar addition in tropical soils on the development of plants. A total of 97 publications on the development of various species, particularly maize (Zea mays) and rice (Oryza), were chosen. The evaluation involved various parameters, which identified positive and negative effects and no significant differences from the control. Some of them also evaluated the contribution of biochar to the development of trees in degraded soils. Tropical soils from 24 different countries, with specific focus on Brazil and Malaysia, were studied. Most biochars were derived from agricultural biomass or wood and produced at temperatures close to 500 degrees C and with alkaline pH (8.3 average value). Subsequently, 25 articles that combined the most studied plant (Z. mays) with the most adopted test type (field) were selected-in this case, the main endpoints evaluated were grain yield and biomass, which generally showed a positive effect or no significant variation in relation to the control. Although the number of studies on biochars has increased in recent years, scientific knowledge shows several gaps, given the variety of physical and chemical characteristics of biochars and the complexity of natural ecosystems. Future research can potentially yield promising results by exploring a wider range of plant species, soil types, and climatic conditions in long-term trials. Appropriate indicators must be considered for assessments of the reduction in negative effects from the addition of biochar on soil health and quality of ecosystem services.