Mycorrhizal activity and diversity in a long-term organic Mediterranean agroecosystem

Arbuscular mycorrhizal (AM) fungi (AMF), fundamental microorganisms for soil fertility, plant nutrition and agroecosystem functioning, may be negatively affected by conventional agriculture. AM fungal activity and diversity following conversion from conventional to organic farming is poorly investigated. Here we studied the effects of short- and long-term organic vs. conventional managements on AM fungal populations of a Mediterranean arable site. Our results shows that AMF activity, as assessed by soil mycorrhizal potential, improved in the activity of the resident AMF, which , even in YngO - 6 years after conversion - was higher than in conventionally cultivated soils and GRSP content are higher under organic farming and increase with time since transition to organic farming, and that AM fungal diversity is affected by the different farming managements. Our results show that soil mycorrhizal inoculum potential, AMF colonisation of maize roots and glomalin-related soil protein (GRSP) content are higher under organic managements and increase over time since transition to organic farming. AM fungal spore populations were different in the diverse farming managements. A progressive enhancement of AM fungal activity and GRSP content from conventionally to organically managed soils shows that organic agriculture is effective in improving biological soil fertility and quality.