Effects of cropping systems under no-till agriculture on arbuscular mycorrhizal fungi in Argentinean Pampas

Here, we compare arbuscular mycorrhizal fungi (AMF) communities and fatty acids in soils under different no-till (NT) agricultural managements over two seasons in two consecutive years. Two NT practices with different agricultural managements were compared: crop rotation (CR) and soya bean monoculture (MC). Soils of natural grasslands (NGs) were used as a reference. Treatments were tested along a regional gradient (four geographical locations) across a 400-km transect of the Argentinean Pampas. We identified 46 morphospecies. Several morphospecies occurred abundantly at all soils; others appeared to be restricted to specific situations. At the regional scale, CR maintained the same richness levels of AMF spores, whereas MC showed less richness, when compared with the NG. Although AMF spore density was clearly affected by cropping practices in the four locations, we could observe some changes in AMF species richness, and similar diversity under agricultural and natural soils. Fatty acid concentrations (whole-cell, phospholipid and neutral lipid fatty acids) revealed differences between soil managements and showed similar patterns of variation in all locations. Spore density positively correlated with all soil lipids fractions. The results suggest that AMF spore communities and fatty acids in soils are suitable indicators of soil management involving different levels of crop rotation. Spore richness measured at a regional scale proved to be sensitive to different NT agricultural managements. Moreover, certain morphospecies could be good bioindicators for NT practices based on cropping systems on the Argentinean Pampas.