Nitrogen efficiency component analysis in wheat under rainfed Mediterranean conditions: effects of crop rotation and nitrogen fertilization

The research was carried out in 1999-01 in a typical Sicilian semi-arid area to evaluate the effect of crop rotation and N fertilization on the nitrogen use efficiency (NUE) in wheat. Crop rotation were: wheat-faba bean, wheat-chickpea, wheat-pea and continuous wheat; nitrogen fertilizer rates were: 0, 40, 80 and 120 kg N/ha. A split-plot design with three replications were used. Analysis of nitrogen efficiency components was performed according to the procedure of Higgins and Pan (1993) using grain yield, aboveground plant N, grain N and post-harvest inorganic soil N. Continuous wheat (WW) recorder the lowest grain yields while no differences were found in wheat grown after the three legumes crops (LW); the yield benefits of LW vs WW declines as fertilizer rates increased. The differences in wheat grain yields were due mainly to N supply component at low N fertilization rates and to NUE at high N rates.