Availability of Sulfur in Sewage Sludge to Plants: A Comparative Study1
- Ahmed A. Elseewi,
- A. L. Page and
- F. T. Bingham2
Alfalfa (Medicago saliva L.), white clover (Trifolium repens L.), and turnip (Brassica rapa L.) were grown on calcareous and acid soils low in available sulfur amended with sewage sludge and gypsum (CaSO4-2H2O) at rates equivalent to 0 and 80 ppm S for alfalfa and 0, 25, 50, and 100 ppm S for white clover and turnip. The availability of S from the two sources was evaluated through measurements of yield, total-S concentration in the plant tissue, S uptake expressed in mg/pot, S recovery, and SO4-S concentration in the soil. Addition of either sludge or gypsum corrected the S deficiency in the plants and significantly increased the dry matter yields. Improvements in yields were associated with increased S concentrations in the plant from deficiency levels (0.010 to 0.088%) to levels ≥ 0.2%. The average ratio of total S concentration in the sludge-treated plants to that in the gypsum-treated plants was 0.83, and the average S uptake and S recovery ratios were 1.09 and 0.95, respectively, indicating comparable availability of S in the two sources. Initial concentrations of NH4-OAc-extractable SO4-S in the soil were increased twofold to sevenfold by application of sludge to the soil. The ratio of post-harvest SO4-S in sludge- and gypsum-treated soils ranged from 0.39 to 2.27 with a mean of 0.95. The results demonstrate that sewage sludge is a potential source of available S to plants.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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