A mycorrhizal fungus grows on biochar and captures phosphorus from its surfaces Edith C. Hammer a, b, c, * , Zsuzsanna Balogh-Brunstad d, e, f , Iver Jakobsen a , Pål Axel Olsson b , Susan L.S. Stipp f , Matthias C. Rillig c a Department of Chemical and Biochemical Engineering, ECO, Technical University of Denmark, Frederiksborgvej 399, 4000 Roskilde, Denmark b Department of Biology, Microbial Ecology/Biodiversity, Lund University, S€ olvegatan 37, 22362 Lund, Sweden c Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB),14195 Berlin, Germany d Department of Chemistry, Hartwick College, One Hartwick Drive, Oneonta, NY 13820, USA e Department of Geological and Environmental Sciences, Hartwick College, One Hartwick Drive, Oneonta, NY 13820, USA f Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, OE, Denmark article info Article history: Received 23 January 2014 Received in revised form 7 June 2014 Accepted 13 June 2014 Available online 3 July 2014 Keywords: Adsorption Charcoal Fertilizer Glomus intraradices Phosphate Slow release abstract Biochar application to soils has potential to simultaneously improve soil fertility and store carbon to aid climate change mitigation. While many studies have shown positive effects on plant yields, much less is known about the synergies between biochar and plant growth promoting microbes, such as mycorrhizal fungi. We present the first evidence that arbuscular mycorrhizal (AM) fungi can use biochar as a physical growth matrix and nutrient source. We used monoxenic cultures of the AM fungus Rhizophagus irreg- ularis in symbiosis with carrot roots. Using scanning electron microscopy we observed that AM fungal hyphae grow on and into two contrasting types of biochar particles, strongly attaching to inner and outer surfaces. Loading a nutrient-poor biochar surface with nutrients stimulated hyphal colonization. We labeled biochar surfaces with 33 P radiotracer and found that hyphal contact to the biochar surfaces permitted uptake of 33 P and its subsequent translocation to the associated host roots. Direct access of fungal hyphae to biochar surfaces resulted in six times more 33 P translocation to the host roots than in systems where a mesh prevented hyphal contact with the biochar. We conclude that AM fungal hyphae access microsites within biochar, that are too small for most plant roots to enter (<10 mm), and can hence mediate plant phosphorus uptake from the biochar. Thus, combined management of biochar and AM fungi could contribute to sustainable soil and climate man- agement by providing both a carbon-stable nutrient reservoir and a symbiont that facilitates nutrient uptake from it. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Biochar is a carbon rich residue of pyrolyzed biomass (com- busted under low oxygen conditions) that as a soil amendment can improve soil fertility. Many governments have recently become interested in investigation of biochar because of its potential in climate change mitigation (Laird, 2008; Sohi, 2012) because char- coal decomposes very slowly in the soil (estimates range from 1000 to 10,000 years; Skjemstad et al., 1998; Krull and Skjemstad, 2003). Soil organic carbon is globally the largest organic carbon reservoir, even when both the biosphere and the atmosphere are included (Lal, 2008). Transfer of carbon from the atmosphere to soil could thus have a large impact on the global carbon balance. Combining biochar production with bioenergy production could even result in a CO 2 -negative balance (Lehmann, 2007a). There are sites in South America where charcoal mixed with feces and bones has been added to soils over a period of several thousand years, resulting in e.g. the Amazonian Dark Earth, or terra preta soils. These soils have significantly higher fertility compared with nearby soils that lack charcoal, and the charcoal is considered at least partly responsible for this (Glaser et al., 2001). Both in field observations and controlled experiments, plant yield has been observed to respond positively to biochar addition, especially in acidic and coarse textured soils (Jeffery et al., 2011). * Corresponding author. Institute of Biology, Plant Ecology of Freie Universit€ at Berlin, Altensteinstr. 6, 14195 Berlin, Germany. E-mail addresses: ehammer@zedat.fu-berlin.de, edith.hammer@gmail.com, edith.hammer@biol.lu.se (E.C. Hammer). Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio http://dx.doi.org/10.1016/j.soilbio.2014.06.012 0038-0717/© 2014 Elsevier Ltd. All rights reserved. Soil Biology & Biochemistry 77 (2014) 252e260