Variation of inorganic sulfur forms under long-term fertilization in purple soil

【Objectives】 A field experiment was established in 1991 in the Long-term Monitoring Network of Purple Soil to investigate effects of long-term fertilization on sulfur (S) with different forms in the soil. The soil samples were collected from the topsoil(0-20 cm) that were treated with no fertilizers (CK), nitrogen, phosphorus and potassium fertilizers(NPK), organic manures(M), NPK plus organic manures (NPKM) and no cultivation (F). 【Methods】 The samples were successively extracted to determine the contents of H2O-S, absorbed-S, HCl-S and total S which were analyzed by the barium turbidity method. 【Results】 The contents of soil total S was increased by 65.42 mg/kg in NPKM compared with the origin samples, while the ratio of available S in NPKM was lower than that in NPK. The content of soil adsorbed-S was improved by 177.4% and 93.3% in NPKM and M compared with the origin samples. Compared with the origin samples, the H2O-S contents of all treatments were decreased by in a range of 0.87-1.38 mg/kg. The content of HCl-S was increased by 161.7% in NPK. 【Conclusions】 The long-term NPK fertilization and NPK plus manure fertilization could significantly increase the availability of S in purple soil, and the NPKM treatment is in favour of S accumulation in soil. In addition, the results from the long-term experiment indicate that the decrease of S input from atmospheric deposition should be concerned.