A field experiment was conducted at Agrinio, West Greece, to compare the impacts of organic vs. conventional farming practices on yield, N nutrition and greenhouse gas emissions in common bean (Phaseolus
vulgaris cv. ‘contender’). In both farming systems, irrigation water containing 0.5 or 10 mM NaCl was
used. The conventionally treated plots were fertilized with an inorganic fertilizer, whereas the organically treated plots received organic compost. Conventional farming resulted in significantly higher fresh
weight of green bean pods than organic farming (5.50 kg m−2
vs. 3.67 kg m−2
, respectively). However, the
cropping system had no impact on dry pod biomass, because the dry matter content of the organically
produced bean pods was higher than that of pods originating from conventional farming (9.88% vs. 7.20%,
respectively). The presence of 10 mM NaCl in the irrigation water restricted significantly the total plant
biomass and fresh pod yield (−22.8%), without any interaction with the farming system. The decrease in
fresh pod yield by organic farming was due to a shortage in soil mineral N (NO3
−
and NH4
+
) at the early
growth stage, which reduced the tissue N levels. Organic farming increased significantly the number or
root nodules at the stage of early pod filling in comparison with conventional farming. However, at both
systems the total soil N increased appreciably at this developmental stage, although no N was supplied
to the crop, thereby pointing to intensive symbiotic N2-fixation by bean. Organic farming resulted in
significantly lower N2O emissions than conventional farming in terms of the overall Global Warming
Potential of the treatments (363 kg ha
−1
vs. 455 kg ha
−1
, respectively). However, the N2O emission intensities did not differ significantly between organic and conventional systems, highlighting the importance
of maximizing yield within organic systems in order to reduce their environmental impac