Soil available sulfur accumulation in a long–term N, P and organic fertilizer experiment under the different cropping systems

Available sulfur accumulation and distribution in soil profile were studied based on the 22 years’ location experiments under the different cropping systems with continuous application of NPM fertilizer. The results show that there are two peaks of available sulfur in soil profiles. The first peak is at 60–80 cm soil depth with the values of 31.3, 29.2，27.9, 25.6 and 24.0 mg/kg under the grain–forage rotation, maize succession, wheat succession, grain–legume rotation and alfalfa succession systems, respectively. The second peak is at 140–180 cm soil depth, and the values in the grain–forage rotation, grain–legume rotation, wheat succession, maize succession and alfalfa succession are 44.7, 43.1, 41.0, 39.7and 36.5 mg/kg, respectively, which are higher than those of the first peak. The accumulation of available sulfur in soil profiles (0–200 cm) under the grain–forage rotation, maize succession, grain–legume rotation, wheat succession and alfalfa succession are 746.3, 640.6, 638.3, 622.4 and 557.3 kg/ha, respectively. The results also indicate that long–time application of P and M fertilizer is the principal factor of influencing the distribution of available sulfur in soil profile under the different cropping systems, and soil available sulfur is transported to deep soils. The results suggest that the differences of sulfur uptake and utilization caused by the different crops and cropping systems have effects on accumulation and distribution of available sulfur in soil profile.