Deep-Rooted Tropical Grasses as Preceding Crops Boost Soil Health and Soybean Yield in Brazil—A Meta-Analysis

Tropical grasses are increasingly present in farming systems in Brazil. However, a national-scale assessment of this practice’s impact on soil health (SH) and soybean yield has been lacking. In this study, we conducted a meta-analysis of 55 studies published until February 2026, comprising field trials run in 33 locations in Brazil, aiming to assess the effects of deep-rooted tropical grasses as preceding crops on biological indicators of SH and soybean yield. Results showed that grasses (Urochloa spp. and Megathyrsus maximus) promote soybean yield by 15%, representing an average increase of 515 kg ha−1 and an additional revenue of US$198 ha−1. The analysis of forage grass species used, management system (single or intercropped), soybean cultivar (growth habit, life cycle, genetic modification), and edaphoclimatic controlling factors revealed positive effects of tropical grasses on soybean yield under all the study conditions and yield ranges. SH indicators also showed sizeable increment, notably the activity of arylsulfatase (+35%) and β-glucosidase (+31%), followed by acid phosphatase activity (+20%), microbial biomass carbon (+24%), and organic carbon (+11%). The results confirmed the beneficial effects of deep-rooted tropical grasses, highlighting their contribution to sustainable intensification in tropical farming systems due to their ability to enhance SH. This, in turn, leads to increased soybean yield under most agronomic and environmental conditions.