INFLUENCE OF A CHANGE FROM TALL FESCUE TO PEARL-MILLET OR CRABGRASS ON THE MYCORRHIZAL FUNGAL COMMUNITY

Crop rotation is a major factor in maintenance of soil productivity in cropping systems, but the role of mycorrhizal fungi has been little c onsidered. A tall fescue (Festuca arundinacea Schreb.) sod heavily inf ected with the Acremonium coenophialum endophyte was plowed, and pearl millet (Pennisetum americanum Leeke) or crabgrass (Digitaria sanguina lis (L.) Scop.) was grown. Pearl millet produced more shoot dry matter and was more heavily colonized than crabgrass, and soil populations o f mycorrhizal fungi were usually higher with pearl millet. Associated with the production of pearl millet and crabgrass were radical changes in the mycorrhizal fungal community. Populations of eight of 19 speci es decreased, four of them not detected at the end of the season. Popu lations of nine increased, five of them not detected at the beginning of the season. Field host and time affected species richness, dominanc e, and diversity; but only time affected equitability. This study sugg ests that crop rotation may be used to manage the mycorrhizal fungal c ommunity. Managing these fungi may be important if individual species or biotypes are found to be pathogenic or mutualistic.