Response of Plant Root Growth to Biochar Amendment: A Meta-Analysis

Abstract

Biochar is widely used in agriculture to improve soil fertility and plant growth. However, a comprehensive assessment of how biochar amendment affects plant root growth is lacking. This study investigated the change in plant root biomass in response to biochar application, including impact factors such as the biochar feedstock and application rate, plant type, and soil pH. The Science Direct, Web Of Science, and Scopus databases were employed to search for literature published before 2021. The published papers with at least three replicates of biochar-amended treatments and a control at the same site were selected for meta-analysis. Our results showed that 165 (81.3%) of 203 datasets from 47 published studies indicated positive effects of biochar amendment on root growth with a mean relative increase of 32%. The feedstocks of biochar and its rate of application were the main factors that determined its effects on plant root growth. The increment of root biomass following biochar amendment was the greatest for trees (+101.6%), followed by grasses (+66.0%), vegetables (+26.9%), and cereals (+12.7%). The positive effects mainly depended on feedstock sources, with the highest positive effect (+46.2%) for gramineous, followed by woody plants (+25.8%) and green wastes (+21.1%). Linear regression analysis and SEM (Structural equation modeling) analysis showed that total nitrogen (TN) and available phosphorus (AK) are one of the most important factors affecting the increase of root biomass. These results suggest that biochar can be considered an effective amendment to improve root growth and soil fertility. Biochar feedstock sources, application rates, and plant types should be considered to assess the potential benefits of biochar for root growth and soil quality.