Contribution of arbuscular mycorrhiza to soil quality in contrasting cropping systems Helena Kahiluoto a, *, Elise Ketoja b , Mauritz Vestberg c a MTT Agrifood Research Finland, Plant Production Research, Lo ¨nnrotinkatu 5, 50100 Mikkeli, Finland b MTT Agrifood Research Finland, Services Unit, 31600 Jokioinen, Finland c MTT Agrifood Research Finland, Plant Production Research, Antinniementie 1, 41330 Vihtavuori, Finland 1. Introduction Arbuscular mycorrhiza (AM) represents an important ecosys- tem service in the capacity of soil to function as a vital system to sustain biological productivity and environmental quality (Karlen et al., 1997; Letey et al., 2003). AM has the potential to promote plant nutrition and growth, and reduce nutrient leaching. Enhanced plant phosphorus (P) uptake is generally considered the main benefit of AM to plants (Abbott and Robson, 1984). AM is a ubiquitous symbiosis in all terrestrial systems and on most plant species, including most agricultural crops. In managed ecosystems, AM is always manipulated – whether intentionally or not – through the plant, soil and/or fungal partner of the tripartite symbiosis. The demand for intentional AM promotion in agricul- ture is increasing due to the scarcity of P deposits, the energy- dependence of their utilisation and concerns about environmental emissions and change. The impact of management systems is of great practical significance to the contribution of AM to crop nutrition and growth and to the environment. As an example, the management benefit, i.e., the increase in AM contribution by omitting the annual P fertilisation of 45 kg ha 1 for 20 years for flax, was 30% of seed dry weight and 35% of seed P content and of total P uptake at harvest (Kahiluoto et al., 2001), while the P emissions to waters were reduced till 11–19% (Kahiluoto, 2000). Understanding manage- ment impact is crucial not only for promoting the functions of field AM fungal (AMF) communities or introduced superior, external AMF, but also for suppressing them in circumstances where they Agriculture, Ecosystems and Environment 134 (2009) 36–45 ARTICLE INFO Article history: Received 4 July 2008 Received in revised form 13 May 2009 Accepted 20 May 2009 Available online 30 June 2009 Keywords: Cropping system Crop rotation Fertilisation rate Green manure Composting Soil quality Arbuscular mycorrhiza (AM) AM effectiveness Ecosystem services ABSTRACT The aim of this study was to determine how the potential to rely on arbuscular mycorrhiza (AM) for plant nutrition differs between a conventional and a low-input cropping system in the long term. The roles of fertilisation rate, composting of recycled plant residues and stage of the rotations in the overall impact of the cropping systems on soil quality and AM were also identified. The conventional cropping system with a non-leguminous crop rotation (barley–barley–rye–oat–potato–oat) was fertilised at either full or half the recommended rate. In the low-input cropping system, one year with barley was replaced by clover, and oat was cultivated mixed with pea. Straw and clover were returned to the soil either with or without composting. In the low-input system, biotite and rock phosphate were used to compensate for K and P in the harvested yield, while animal manure was applied at the start only. After 15 years, crop growth and nutrition, AMF colonisation and soil quality were assessed in the field, while the AM contribution to growth and nutrient uptake were determined in a bioassay in a growth chamber. AM functioning made a higher contribution to soil quality in terms of crop performance and environmental benefits in the low-input cropping system than at either fertilisation rate in the conventional system. Halving fertilisation in the conventional system prevented some costs and enhanced some of the benefits of AM in comparison with full fertilisation. However, only the low-input system with composting conclusively favoured AM in comparison with the conventional system. It resulted in the highest percentage colonisation and, in a bioassay with flax and clover, gave a relative average contribution to growth of 27% and to P uptake of 68% in comparison with 4 and 36%, respectively, for the conventional cropping system with full fertilisation. Rye yield was in the low-input system without composting similar to that in the conventional system with full fertilisation, and with composting 87% of the latter one. Incorporation of clover green manure without composting inhibited AM functioning, leading to a temporary loss of AM contribution to crop performance. This effect draws attention to the impact of the form of recycled organic matter on supporting ecosystem services such as nutrient cycling. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +358 405118335; fax: +358 15226578. E-mail address: helena.kahiluoto@mtt.fi (H. Kahiluoto). Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee 0167-8809/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2009.05.016