Impact of long-term conventional and organic farming on the diversity of arbuscular mycorrhizal fungi

F. Oehl¹, E. Sieverding², P. Mäder³, D. Dubois⁴, K. Ineichen¹, T. Boller¹ and A. Wiemken¹

Abstract
Previous work has shown considerably enhanced soil fertility in agroecosystems managed by organic farming as compared to conventional farming. Arbuscular mycorrhizal fungi (AMF) play a crucial role in nutrient acquisition and soil fertility.

The objective of this study was to investigate the diversity of AMF in the context of a long-term study in which replicated field plots, at a single site in Central Europe, had been cultivated for 22 years according to two organic and two conventional farming systems. In the 23rd year, the field plots, carrying an 18-month-old grass-clover stand, were examined in two ways with respect to AMF diversity.

Firstly, AMF spores were isolated and morphologically identified from soil samples. The study revealed that the AMF spore abundance and species diversity was significantly higher in the organic than in the conventional systems. Furthermore, the AMF community differed in the conventional and organic systems: Glomus species were similarly abundant in all systems but spores of Acaulospora and Scutellospora species were more abundant in the organic systems.

Secondly, the soils were used to establish AMF-trap cultures using a consortium of Plantago lanceolata, Trifolium pratense and Lolium perenne as host plants. The AMF spore community developing in the trap cultures differed: after 12 months, two species of the Acaulosporaceae (A. paulinae and A. longula) were consistently found to account for a large part of the spore community in the trap cultures from the organic systems but were found rarely in the ones from the conventional systems.

The findings show that some AMF species present in natural ecosystems are maintained under organic farming but severely depressed under conventional farming, indicating a potentially severe loss of ecosystem function under conventional farming.


Source
Oecologia (2004) 138: 575-583


Author Locations & Affiliations
(1) Botanisches Institut, Universität Basel, Hebelstrasse 1, 4056 Basel, Switzerland
(2) Institute of Plant Production and Agroecology in the Tropics and Subtropics, University of Stuttgart Hohenheim, Garbenstrasse 13, 70593 Stuttgart-Hohenheim, Germany
(3) Research Institute of Organic Agriculture, Ackerstrasse, 5070 Frick, Switzerland
(4) Swiss Federal Research Station for Agroecology and Agriculture (FAL), Reckenholzstrasse 191, 8042 Zürich-Reckenholz, Switzerland


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Posted March 2010