Biostimulant Applications Improve Crop Root Morphology in Agricultural Systems: A Global Meta-Analysis

Biostimulant applications may alleviate various stresses and improve the yield of crops, thus contributing to the promotion of crop growth and development in agricultural systems. Despite these potential benefits, the effects of biostimulants on root morphological traits remain poorly understood. In the present study, a global meta-analysis of 111 peer-reviewed publications was conducted to quantify the effects of biostimulant applications on various root morphological traits and identify the determining factors. Compared to untreated controls, biostimulant applications significantly increased the primary root length by 14.7%, total root length by 17.7%, root biomass by 24.5%, root activity by 21.7%, root diameter by 4.0%, root-to-shoot ratio by 2.4%, root volume by 25.7%, root surface area by 15.6%, root tips by 15.4%, and root forks by 15.6%. The biostimulant type and crop species were identified as the main moderators of root morphological responses. Among various biostimulants, humic acid showed the most consistent and pronounced positive effects. Additionally, orchard and vegetable crops exhibited greater responsiveness than grain crops. These findings provide quantitative evidence that biostimulants promote root system development across diverse crop species. They also underscore the potential of biostimulants to enhance nutrient acquisition and support more sustainable agricultural production.