Sulphur demand, uptake and fertilization of Vicia faba L. under field conditions

Under the given environmental conditions, fertilizing the faba bean did not influence seed yields. S accumulation in the shoots of plants from different sites only ranged from 9 to 11 kg S ha−1, whereas the seeds accumulated the bulk of the absorbed S (average S harvest index: 0.65). Optimal growth in the youngest open leaf at flowering was achieved with a N:S ratio of about 20.5 and a corresponding S concentration at 0.29% in the leaves' dry mass. Obviously, the content of plant-available S in the soil combined with the atmospheric S deposition at the testing environments fulfilled the beans' S requirement as the additional S fertilization did not produce any effects in yield. The apparent S recovery from the kieserite, gypsum and epsom salt fertilizers - which generally provide plant-available S - was comparatively low, exhibiting values of 3.16%, 5.35% and 8.94%. However, these three fertilizers still generated noticeable increases in S accumulation in parts of the plant. Kieserite and gypsum significantly increased the S concentration in the seeds and straw while narrowing the crop's N:S ratios. Foliar fertilization with epsom salt exhibited the most apparent S recovery among the tested fertilizers. This analysis deems it unlikely that Elemental S will increase S concentration in faba bean in the year of application or narrow the plant's N:S ratio. These results show that fertilizing faba bean with S does not currently appear to be necessary when cultivated under conditions similar to the tested environments.