Based on the long-time location exeriments,accumulation and distribution of available sulfur in soil of different cropping systerms under the condition of 22 years continuous application of NP chemical fertilizer in Loess Plateau were studied.The results showed that there are two peaks of available sulfur in soil profiles.The first peak occurred in 60-80 cm soil depth with the values of 27.07 mg/kg,25.42 mg/kg,24.23 mg/kg,22.61 mg/kg,16.56 mg/kg and 15.14 mg/kg in maize-wheat(2 a)+millet rotation,pea-wheat...
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