Effect of biochar addition on soil respiration partitioning and root dynamics in an apple orchard

Summary Biochar addition to soil has been suggested as a promising strategy to increase soil carbon storage with important side‐effects on soil fertility and crop productivity. Understanding the effect of biochar on soil respiration partitioning into rhizosphere‐derived ( F r ) and soil organic carbon‐derived ( F soc ) components and on plant root dynamics and microbial activity is a crucial issue in the prediction of the impact of biochar on soil organic carbon and nutrient cycles. Within this framework, an experiment was carried out in an apple ( Malus domestica B ork) orchard located in the experimental farm of the B ologna U niversity ( I taly). In spring 2009, 10 t of biochar per hectare were incorporated into the surface 20‐cm soil layer by soil ploughing. The trenching method was used in order to partition total soil respiration ( F s ) into F r and F soc components in both biochar‐treated and control soil. Soil respiration measurements were performed from J une 2009 to M arch 2011. To study root dynamics, polycarbonate boxes were built and buried into the soil. Soil profile pictures were collected fortnightly with a CCD sensor scanner inserted in the boxes and analysed with the WinRHIZO T ron MF software. Biochar addition increased F soc and reduced F r , even if the root length intensity ( L a ) increased in biochar‐treated soils relative to that in the control. A decrease in root metabolic activity was postulated to explain these contrasting results.