The functioning of arbuscular mycorrhizal fungi in land under different agricultural management intensities.

In recent decades the proportion of agricultural land in the UK and Europe under organic management, or other low-input forms of agriculture, has risen sharply. Conventional, intensive, agriculture employs techniques which have been shown to be detrimental to arbuscular mycorrhizal fungi, such as ploughing, fertilisation, pesticide application, and the growth of non-host crops. The impacts of low-input agriculture on arbuscular mycorrhiza and their functioning have been little studied, and this thesis examines the functioning of arbuscular mycorrhizal fungi (AMF) from land under different agricultural management regimes.
Using radioisotope labelling, it was found that phosphorus transfer through AMF hyphae to plants was far higher in turfs from organic pasture than from conventional pasture, integrated wheat fields or conventional wheat fields: 60 days after labelling the mean hyphal uptake of 33p was over 14 times greater in shoots from the organic pasture than in any of the other management treatments. Further experiments using turfs from organic and conventional fields and their margins showed a trend of decreased AMF hyphal phosphorus transfer to plants in conventional than organic farmland, and in fields compared to field margins. This trend was reversed for the 14C-carbon transfer from shoots to AMF hyphal compartments. Hyphal respiration of 14CO2 was 25 % greater in turfs from conventional than organic fields. Using the ratio of hyphaI carbon transfer to hyphal phosphorus transfer to infer the degree of mutualism of the AMF present, it was shown that AMF in land under organic management were significantly more mutualistic than those in land under conventional management, but that there was no significant effect of whether the turf was from a field or a field margin.
These results confirm the major detrimental impacts of conventional farming practices upon AMF, and that organic management has a lower impact upon AMF functioning.