The development of reduced tillage in cropping systems raises the question of adaptation of N fertilization of crops in response to changes in the chemical, physical and biological soil caused by the cessation of ploughing. The purpose of the work was to investigate the fate of fertilizer (15)N applied in spring to a winter wheat crop (Triticum aestivum L) under minimum tillage (MT) and conventional tillage (CT) and to examine the hypothesis that in MT systems plants face stronger microbial competition for N. The experiment was conducted in Northern France on a silt loam in two different rotations [sugar beet (Beta vulgaris L)-winter wheat-maize (Zea mays L)-winter wheat and seed flax (Linum usitatissimum L.)-winter wheat-pea (Pisum sativum L)-winter wheat] from which we selected two crop sequences, pea-wheat and maize-wheat. At the beginning of stem elongation, (15)N labelled fertilizer was applied at the rates of 100 kg N ha(-1) for wheat after pea and 120 kg N ha(-1) for wheat after maize. The dynamics of fertilizer (15)N in soil and plant was assessed at six dates between N application and wheat harvest. In addition, soil respiration was monitored continuously on the maize-wheat CT and MT plots as a way of assessing heterotrophic microbial activity. The type of tillage (MT vs CT) had little effect on fertilizer N dynamics in the soil. The amount of labelled N immobilized was low with values ranging from 3.5 to 11.9% of applied (15)N. Plant (15)N recovery (above ground biomass + roots) amounted to 59-63% at flowering and harvest. The (15)N balance at harvest time (i.e. the sum of (15)N recovered from all plant and soil compartments) indicates that approximately 29% of the fertilizer N applied was lost whichever the tillage considered. The type of rotation (i.e. the nature of the preceding crop) had more influence on wheat N uptake than the type of tillage. The lack of observed effect of tillage on the dynamics of nitrogen fertilizer and plant recovery is in agreement with most published results obtained in other soil and climate conditions.