Effect of tillage and farming system upon VAM fungus populations and mycorrhizas and nutrient uptake of maize

Low-input agricultural systems that do not rely on fertilizers may be more dependent on vesicular-arbuscular mycorrhizal [VAM] fungi than conventional ly managed systems. We studied populations of spores of VAM fungi, mycorrhi za formation and nutrient utilization of maize (Zea mays L.) grown in moldb oard plowed, chisel-disked or no-tilled soil under conventional and low-inp ut agricultural systems. Maize shoots and roots were collected at four grow th stages. Soils under low-input management had higher VAM fungus spore pop ulations than soils under conventional management. Spore populations and co lonization of maize roots by VAM fungi were higher in no-tilled than in mol dboard plowed or chisel-disked soil. The inoculum potential of soil collect ed in the autumn was greater for no-till and chisel-disked soils than for m oldboard plowed soils and greater for low-input than conventionally farmed soil. The effects of tillage and farming system on N uptake and utilization varied with growth stage of the maize plants. The effect of farming system on P use efficiency was significant at the vegetative stages only, with hi gher efficiencies in plants under low-input management. The effect of tilla ge was consistent through all growth stages, with higher P use efficiencies in plants under moldboard plow and chisel-disk than under no-till. Plants grown in no-tilled soils had the highest shoot P concentrations throughout the experiment. This benefit of enhanced VAM fungus colonization, particula rly in the low-input system in the absence of effective weed control and wi th likely lower soil temperatures, did not translate into enhanced growth a nd yield.