Soil quality assessments in integrated crop-livestock-forest systems: A review

Integrated crop-livestock-forest is a promising strategy to improve soil quality. It comprises four different integrated farming systems: crop-livestock, crop-forest, forest-livestock and crop-livestock-forest. This work systematically reviewed studies about integrated crop-livestock-forest systems and soil quality. A total of 92 papers were retrieved from the Web of Science-Clarivate Analytics platform, and the following information was analysed: publication year, institution, region of the studied site, type of integrated system, soil type, tillage system, maximum soil depth and the soil quality indicators assessed. Most studies were published in the second half of the 2010s. Brazil is a prominent focus of research about soil quality and integrated crop-livestock-forest systems, with significant contribution from its central and southern regions. The Embrapa was the main publishing institution, present in over one-third of the studies. Crop-livestock was the most common integrated system, Ferralsols was the most common soil group, and most of the studied soils were clayey. No tillage was the main tillage system. Most studies focused on the topsoil, assessing physical and/or chemical soil quality indicators. More emphasis on biological indicators of soil quality is required, as well as assessments integrating biological, physical and chemical indicators of soil quality. Future works should compare different integrated systems, including assessments deeper in the soil profile, especially in systems with the forest component, and also in sandy and silty soils. Soil quality indicators that have been rarely used should be further tested. Novel indicators should be added to better understand the promotion of soil quality by integrated crop-livestock-forest systems.