MANAGEMENT INFLUENCES ON ARBUSCULAR MYCORRHIZAL FUNGAL SPECIES COMPOSITION IN A CORN-SOYBEAN ROTATION

Crop and edaphic factors influence arbuscular mycorrhizal (ARI) fungal species composition and populations, This study was conducted to dete rmine the effect of management history, crop, and input system on spec ies composition of AM fungal spore populations. Corn (Zen mays L.)-soy bean [Glycine max (L.) Merr.] sequences receiving no inputs (NI), orga nic inputs (OI), minimum inputs CMD, and conventional inputs (CI) were established in two adjacent areas with differing management histories : one area, the Koch Farm, had received no fertilizer or herbicide inp uts for the past 25 yr; the other area, the experiment station, receiv ed recommended herbicide and fertilizer inputs, Fifteen AM fungal spec ies were found in a survey of mycorrhizal fungal spore populations, Gl omus aggregatum populations were positively correlated with Setaria sp p. populations (r = 0.56), pH (r = 0.47), and K (r = 0.25) and negativ ely correlated with soil P (r = -0.57), Populations of GI. geosporum, Gl. leptotichum, Gl. macrocarpum, and Gl. occultum were also positivel y correlated with soil pH and negatively correlated with soil P Gigasp ora margarita spore populations were positively correlated with soil P level (r = 0.272). Although species richness was greater (13 species vs, 10), species diversity (H-w) was lower at the Koch Farm than the e xperiment station (0.57 vs. 0.64) because of large Gl. aggregatum spor e populations. The correlation of AM fungal spore populations with Set aria spp. and P, K, and pH indicates that management practices influen ce AM fungal species composition through both biotic and abiotic facto rs.