Changes in soil nutrient availability explain biochar's impact on wheat root development

Biochar is a carbon-rich product obtained from the pyrolysis of organic materials. Its use, combined with fertilizers, can modify soil properties and affect root morphology and functioning. The main objective of this study was to evaluate the impact of biochar and fertilizer addition on root development and morphology. Durum wheat was pot-grown for 2 months using two types of biochar (produced from wheat straw and olive-tree pruning) applied at four rates (0, 0.5, 1 and 2.5 % w/w) and combined with three fertilization levels (0, 40 %-low and 100 %-complete). Biochar addition at high rates increased the specific root length and decreased both root diameter and root tissue mass density, indicating a fine root proliferation, regardless of the fertilization level. This may have favoured the resource acquisition by increasing biochar-root interactions, soil exploration and the fertilizer efficacy. Biochar addition reduced N and Mn availability but increased P availability, which also influenced root growth. Changes in root morphology may therefore serve as an important indicator of soil changes induced by biochar and its study can contribute to a better understanding of the effects of the combined application of biochar and fertilizers on plant growth.