Tillage and farming system affect AM fungus populations, mycorrhizal formation, and nutrient uptake by winter wheat in a high-P soil

Abstract

AbstractWe conducted a field study at the Rodale Institute Experimental Farm, Kutztown, Pennsylvania, in a high-P soil to examine the interaction of farming system and tillage on the potential functioning of arbuscular mycorrhizal (AM) fungi. Plots under conventional and low-input systems were either chisel-disked or no-tilled. Winter wheat was planted following the harvest of soybean, and shoots and roots were collected at tillering, jointing, heading, and ripening. Spores of AM fungi were isolated from soil collected at the beginning and end of the growing season. Spore populations and colonization of winter wheat roots by AM fungi were higher under low-input than conventional agriculture. Mycorrhizal fungus colonization occurred at low levels in the tillering stage and increased with plant development. Colonization during the jointing stage was higher in the low-input, no-tilled than in low-input, chisel-disked plots. Spore populations of theGlomus occultum-type group were more numerous in no-tilled than in tilled soil. The nutrient-use efficiency (g of plant biomass per g of plant N or P) of winter wheat depended on plant developmental stage, with a tendency for higher efficiency of the low-input plants at early growth stages, and of conventionally managed plants at more mature stages. Overall, plants grown in chisel-disked plots had higher N and P utilization efficiencies than plants grown in no-tilled plots. Final yield of grain was significantly greater in conventional than low-input plots, especially for no-till, despite the larger population of AM fungi.