Effects of season and soil conditions on the mycorrhizal status and colonization of seven grass species. Mahmood Ghorbani*, Jalil Khara and Nasser Abbaspour

In this study seven plant species were collected from the forest of Arasbaran located in the northwest of Iran. Sampling was conducted in May and August and roots were used for calculating vesicular arbuscular mycorrhizal colonization percentage during the same period. Fine roots were separated, washed and put in FAA solution as a fixative. Through the time, root colonization of all plant species increased significantly. Soil collected from rhizosphere of each plant species was physico-chemically analyzed and spore number was determined. Similar to VAM colonization of roots, spore population per 1 gram rhizosphere soil of all plants except Melilotus officinalis increased through the time. Rhizosphere soils were used for analysis of EC, pH and soil available N, P and K. Soil texture also was analyzed. Soil EC had very high correlation (r = 0.923, p < 0.05) with spore number and pH had high but negative correlation with both spore number and vesicular arbuscular mycorrhizal root colonization. Among the soil available nutrients, N showed high correlation with root colonization and specially spore populations.