The roles of mycorrhiza and Penicillium inoculants in phosphorus uptake by biochar-amended wheat

Biochar (BC) application to soil can potentially replace mineral P fertilizers and its effectiveness as fertilizer can be improved by plant inoculation with the phosphate-solubilizing microorganism Penicillium aculeatum (Pa). Arbuscular mycorrhiza (AM) fungi are important in plant P nutrition and may possibly act synergistically with Pa to improve the uptake of BC-P. Responses in wheat to inoculation with Pa and the AM fungus Rhizophagus irregularis were studied in a pot experiment at two levels of BC fertilization. Pots contained a mesh-enclosed, root free compartment with 33P-labelled soil for assessment of the AM contribution to P uptake and for studying if Pa would affect P uptake by the AM fungal hyphae. AM application suppressed wheat growth, albeit AM pathway had a major role in total P uptake at the two lowest P levels (nil or 20 mg BC-P kg−1 soil). Moreover, AM contribution had similar magnitudes in the presence and absence of Pa. Rhizosphere and bulk soil were actively colonized by Pa, both in the presence and absence of AM. The application of Pa or BC at a low rate increased AM-colonized root lengths. Although this was not translated to increased P uptake by wheat, the results suggest that AM and Pa can be combined without showing antagonistic interactions. However, more work is needed to understand how AM and Pa can be combined to increase plant growth.