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A field experiment established in 1962 on a luvisol derived from loess was chosen to investigate the effect of long-term application of farmyard manure, compost and sewage sludge, respectively, in two increments on inorganic and organic S fractions in bulk soil. Compared with mineral fertilizer, the high application rates of the different organic fertilizers (10 t farmyard manure (FYM2), 29 t compost (COM2), 7.44 t sewage sludge (SS2)/ha/year, respectively), resulted in an increase of the total S content in the bulk soil: 220 mg/kg (FYM2), 298 mg/kg (COM2), 277 mg/kg soil (SS2) as compared to the control (MIN) with 158 mg/kg soil. The sum of water soluble plus adsorbed S was significantly higher in the treatments with the high amount of compost (17.9 mg/kg soil) and sewage sludge (16.4 mg/kg) soil as compared to all the other treatments (10.0 to 13.1 mg/kg soil). The treatments with the high amounts of organic manures contained lower contents of ester sulfate and higher contents of C-bonded S as compared to the treatments with the low amounts, and vice versa.
Forster et al. (Tue,) studied this question.