Relationship of plant available sulphur with soil characteristics,rainfall and yield levels of oilseed crops in Pothwar Pakistan

A study was carried out in order to assess the status of plant available s in the 15 rain-fed arable soils of pothwar,pakistan and to evaluate its relationships with soil characteristics,rainfall distribution and yield levels of oilseed crops in the region. the contents of plant available s (0.01 m cacl2 extractable so4 -2-s) in the soils varied from 5.7 to 21.7 μg g-1 soil (mean 11.7 μg g-1 soil) and corresponded to 7.0 to 13.8% of the total s in the soils. the adsorbed s contents ranged from 1.9 to 7.8 μg g-1 soil (mean 4.8μg g-1 soil) forming 2.0 to 7.3% of the total s in the soils. the organic s contents ranged from 68.4 to 140.4 μg g-1 soil (mean 97.0 μg g-1 soil) accounting for 81.5 to 89.3% of the total s in the soils. the 0.01 m cacl2 extractable so4 -2-s was highly significant positive correlated with total s and organic s in the soils. significant positive relationships also existed between 0.01 m cacl2 extractable so4 -2-s and the clay,ece,organic c,total n,and extractable p contents in the soils. significant negative relationships of 0.01 m cacl2 extractable so4 -2-s were observed with the caco3 and phs of the soils. among the climatic factors,0.01 m cacl2 extractable so4 -2-s showed significant positive correlation with the mean annual temperature,while the significant negative relationships with rainfall from july to august,total annual rainfall and the rainfall from september to june. a strong positive relationship existed between 0.01 m cacl2 extractable so4 -2-s contents and the average yield level of oilseed crops (r = 0.80**). among different crops,groundnut yield had highly significant correlation (r = 0.90**) with the cacl2 extractable so4 -2-s followed by the sunflower (r = 0.70**),while the rapeseed/ mustard yield had the lowest (r = 0.59*).