6 Australian Journal of Crop Science     3(1):6-12 (2009)  ISSN: 1835-2707 Impact of olive pomace wastes and fungicide treatment on indigenous arbuscular mycorrhizal fungi associated with chickpea (Cicer arietinum L.) under field conditions 1* Assaf TA, 2 Turk MA and 2 Hameed KM 1* Department of Grassland Science, Georg August University, Germany 2 Department of Plant Production, Jordan University of Science and Technology, Jordan *Corresponding author: tassaf@gwdg.de Abstract The effect of soil amendment with olive pomace wastes (OPW) on population and root infection of indigenous arbuscular mycorrhizal (AM) fungi associated with chickpea has been studied under field conditions. Yield components, phosphorus (P) percentage, AM spore density and root length colonization of AM fungi were recorded. We found that OPW increased biomass, seed yield, and shoot phosphorus concentration of chickpea plants. Our results also indicated that AM fungal spore population and colonization levels were substantially enhanced by the application of OPW. Fungicide applications significantly decreased both spore population and colonization length of AM fungi. We concluded that organic matter amendments potentially increased AM fungal association and hence might increase growth and yield of chickpea plants in the field. Key words: Microorganisms; Organic matter; Olive pomace; Soil amendment; Spore populations. Abbreviations: AM fungi- arbuscular mycorrhizal fungi; OPW- olive pomace wastes. Introduction Most legumes are symbiotically associated with Arbuscular mycorrhizal (AM) fungi and rhizobia. The beneficial effect of these symbiotic relationships on plant growth is well documented. However, in cultivated soils, the populations as well as the infectivity of AM fungi may be affected by cultural practices such as soil amendment with organic matter. It was reported that AM fungi usually increase as a result of soil amendment with organic matter which leads often to the benefit of plant from this relationship (Ryan et al., 1994; Douds et al., 1997). This result might be explained by the effect of organic matter on soil structure, water retention capacity, microbial activity, or chemicals released from organic matter (Ryan et al., 1994). Olive pomace wastes (OPW) are produced in large quantities in many Mediterranean countries during November-February (Mechri et al., 2008). Once the olives have been ground into a paste, the paste is separated into three components; vegetable water, oil, and the husk. The husk (pomace) contains the skins, pulp and pit fragments. Olive pomace could be applied to the soil, either intentionally as soil amendment or unintentionally as a disposal method. Al-Sakit and Al-Momani (1989) found that OPW treatment improved the growth of olive seedlings when applied as a fertilizer. However, it has been found that the yields of wheat and barley were decreased as a response to soil amendment with OPW and this was attributed to the presence of phytotoxic