A meta-analysis of the agronomic benefits of silicate rock powders in Brazil in the context of a novel classification

Philipp Swoboda, Eder de Souza Martins, Gisele Freitas Vilela, Luis Ferreira, Carlos Augusto Posser Silveira, Giuliano Marchi, Mariane Chiapini, Marcella Daubermann, Mayra Maniero Rodrigues, Matthew Oliver Clarkson, Junyao Kang, Veronica Furey, David Manning, Christina Larkin

Brazil has emerged as a global leader in the use of silicate agrominerals (ASi), silicate-rich rock powders that supply plant nutrients and improve soil properties. These materials could advance low-cost soil-sustaining crop production, particularly in the deeply weathered and nutrient-depleted soils of the tropics. However, the research landscape remains fragmented, and there is currently no quantitative synthesis of tropical ASi  assessments. We address this gap by synthesising 54 Brazilian crop trials through a meta-analysis structured around a recently proposed ASi classification. Pooled across all classes, ASi delivered significant (p<0.01) gains in grain yield (+33%), aboveground biomass (+42%), exchangeable Ca (+38%), Mg (+35%) and K (+19%), soil pH (+4%), and P (+80%), confirming ASi as a robust multi-nutrient amendment for highly weathered tropical soils. The novel classification could empirically discriminate among the agronomic effects of the ASi classes. A conservative single-season economic analysis shows that basalt and phonolite powder can achieve a breakeven under real field conditions at moderate doses. We recommend minimum requirements for standardised methodologies and suggest real-world research designs to support broader ASi adoption. Our findings offer valuable insights for scaling the usage of ASi across tropical agricultural systems worldwide, contributing to sustainable food production and climate resilience.