Speciation distribution of soil inorganic sulfur in three black soil areas of Northeast China

Using field sampling and step-extraction method, this paper analyzed the distribution and fraction characteristics of soil inorganic sulfur in three black soil zones in Northeast China. The results showed that inorganic sulfur in the top 0~20 cm black soil accounted for 22% of total sulfur. Then of the total inorganic sulfur, H₂O-S accounted for 6%, adsorbed-S for 3% and HCl-S accounted 13%. The order of H₂O-S and adsorbed-S content in the black soil zones was Hailun > Bei’an > Gongzhuling. That of HCl-S was Gongzhuling > Hailun > Bei’an. Soil H₂O-S and adsorbed-S changed little with increasing soil profile depth. Below 115 cm soil depth, HCl-S began to accumulate. Soil H₂O-S and adsorbed-S exhibited significant positive correlations with organic matter, CEC (cation exchange capacity) and content of clay smaller than 0.002 mm. Soil H₂O-S and adsorbed-S correlated with pH negatively. A significant positive correlation was noted between soil HCl-S and soil electrical conductivity. Total inorganic sulfur and HCl-S contents decreased with increasing period of land cultivation in Hailun black soil zones.