Changes in root traits explain the variability of biochar effects on fruit production in eight agronomic species

Abstract

Biochar (BC) application to soil could increase soil C sequestration, soil fertility, and crop production, which makes it an interesting soil amendment for organic agriculture. However, studies to date show a great variability in their results, depending on the plant species studied. Our hypothesis is that the different root responses of the species to the addition of BC may explain the high variability of BC effects on yield. We investigated the effects of addition of olive-tree pruning BC applied to soil at 5% w/w on soil properties, root morphology, and crop yield in a greenhouse pot experiment. We used eight species of agronomic interest: Brassica napus L., Capsicum annuum L., Cicer arietinum L., Glycine max L., Gossypium herbaceum L., Solanum lycopersicum L., Solanum melongena L., and Zea mays L. Addition of BC reduced soil bulk density and increased both soil water content and nutrient availability. BC addition had an influence on many plant traits as it increased the specific root length, specific leaf area, and leaf relative water content. Also, the BC addition increased aboveground biomass and fruit production. Interestingly, the increase in fruit production was positively correlated with the changes in specific root length. Our results support the hypothesis that the most responsive species to BC addition through changes in root traits may be those that increase more fruit production.