Successive cultivation of maize and agricultural practices on root colonization, number of spores and species of arbuscular mycorrhizal fungi

RESUMO

A large number of propagules and a broad spectrum of species are two important components of ecosystem (including agroecosystem) sustainability. Previous studies carried out in temperate areas showed that repeated monoculture leads to a decrease in the species abundance of arbuscular mycorrhizal fungi (AMF). This study evaluated the influence of maize monoculture and its agricultural practices on AMF during three consecutive cropping years in a Brazilian field. At the end of each cycle, soil and root samples were evaluated for species composition, spore populations and root colonization by AMF. The AMF community present during this period was scored according to the Spearman rank correlation and Principal Components Analysis. The mean percent root colonization values for the three cultivation values for the three cultivation periods were 66.9,60.7 and 70.5, respectively. Seven species were detected in the first year, Scutellospora persica being the most abundant 24.1 (per cent of spores) and Glomus macrocarpum the most observed 100 (per cent of samples). In the second year, Glomus etunicatum was the species with the greatest number of spores 24.7 (per cente and, like G. macrocarpum, the mostfrequently observed 90 per cente in a community of thirteen. In the third year, twenty-three AMF species were identified, Scutellospora sp.1 being the most abundant 17.4(per cent), and Gigaspora decipiens and Glomus claroideum the most frequent (both with a relative frequency of 70 (per cente). The main soil factors influencing root colonization and sporulation by AMF were pH (and related properties), phosphorus and organic matter contents.