XVI International Botanical Congess

Soil organic matter (SOM), water-stable aggregate (WSA) formation and AM fungal activity are important indicators of soil quality. Conventional agriculture, pasture, modified milpa and forest sites were evaluated for the above parameters. AM activity was assessed using spore counts and root colonization bioassays. Conventional sites exhibited degraded SOM and loss of largest WSA. AM populations were maintained, but species compositional changes merit study. The slash-mulch milpa system conserved SOM and structure. Recent shortening of the rotation cycle may negatively impact these parameters. Spore counts indicated that AM activity is maintained in the milpa system. Cropped site infectivity is low, but increases in soil from regenerating sites. Mycorrhizae may be more important for the regenerating vegetation than the maize crop.