Response of arbuscular mycorrhizal fungi infectiveness to soil nitrogen supply

Arbuscular mycorrhizal fungi (AMF) as important root symbionts should be regarded as a vital component of the terrestrial ecosystems. The most of higher plants including the great majority of economically important crops, vegetables, fruits and ornamentals are able to form symbiosis with AM fungi. AMF mainly help plants in mineral nutrient acquisition from soil, but other beneficial effect of these fungi have been described (Takacs & V6r6s, 2003). AMF can significantly enhance water and macro-, microelement uptake and health of host plants and even their tolerance to environmental stresses (drought-, salt-, toxic element etc.) is increased by the presence of symbiosis. Numerous publications have investigated the relationship between the AMF root colonization, mycorrhizal dependency of host plants and phosphate supply of the soil. However the effect of nitrogen fertilization on the infectiveness of AMF is not clear yet. Nitrogen (N) is the main limiting element in plant developing and nutrition (Csathb et al. 2005). In high-input agricultural soils ploughing, fertilisation and fungicide application may reduce the colonization of AMF that results in the decrease of their efficiency on host growth and nutrient uptake. Developing a new soil management technology for sustainable agriculture the role and functions of soil microbial community should be considered. The aim of this study was to investigate the effect of various nitrogen treatments (0, 50, 100, 150 mg NH4NO3 kg"') on the rate of Glomus mosseae colonization (infectiveness) using bean (Phaseolus vulgaris L.) test plants in a pot trial on a calcareous chernozem soil from NagyhorcsOk (Hungary).