1 Risø National Laboratory for Sustainable Energy, Technical University of Denmark2 unknown3 Department of Chemical and Biochemical Engineering, Technical University of Denmark
An experiment was set up to investigate the role of arbuscular mycorrhiza (AM) in utilization of P from organic matter during mineralization in soil. Cucumber (Cucumis sativus L.) inoculated with one of two AM fungi or left uninoculated were grown for 30 days in cross-shaped PVC pots. One of two horizontal compartments contained 100 g soil (quartz sand : clay loam, 1:1) with 0.5 g ground clover leaves labelled with P-32. The labelled soil received microbial inoculum without AM fungi to ensure mineralization of the added organic matter. The labelling compartment was separated from a central root compartment by either 37 mu m or 700 mu m nylon mesh giving only hyphae or both roots and hyphae, respectively, access to the labelled soil. The recovery of P-32 from the hyphal compartment was 5.5 and 8.6 % for plants colonized with Glomus sp. and G. caledonium, respectively, but only 0.6 % for the non-mycorrhizal controls. Interfungal differences were not related to root colonization or hyphal length densities, which were lowest for G. caledonium. Both fungi depleted the labelled soil of NaHCO3-extractable P and P-32 compared to controls. A 15-25 % recovery of P-32 by roots was not enhanced in the presence of mycorrhizas, probably due to high root densities in the labelled soil. The experiment confirms that AM fungi differ in P uptake characteristics, and that mycorrhizal hyphae can intercept some P immobilization by other microorganisms and P-sorbing clay minerals.
Plant and Soil, 1994, Vol 163, Issue 2, p. 203-209