Movement of S35 Tagged Sulfate Through Soil Columns
1962
Chao, Tsun Tien | Harward, M. E. | Fang, S. C.
Soil columns were used to study the movement of S³⁵ tagged sulfate applied as gypsum (CaSO₄ · 2H₂O) through soil systems as influenced by different rates of water and sulfur applications, and of fertilizer treatments. With different rates of water, the distribution of the surface-applied sulfate showed a well-defined pattern of gradual downward movement. Increasing the rate of sulfate applied in conjunction with a given amount of water resulted in a greater total amount of sulfate moving through the columns. The distribution of sulfate on a percentage basis, however, was independent of the amount of sulfate applied. The data suggest that the retained sulfate ions were in kinetic equilibrium with those in solution. Both lime and phosphate treatments were shown to increase the movement of sulfate in column studies. The effect of lime was much greater, however, than the effect of phosphate. The results of equilibration studies were in good qualitative agreement with those from column studies. Differences caused by fertilizer treatments with respect to degree of sulfate movement in columns were dependent on the nature of the soils used. Of the 15 soils examined, one Reddish Brown Lateritic, two Brown Latosols and an Ando soil showed appreciable ability to hold sulfate ions against leaching. These soils also contained a much higher content of free aluminum and iron oxides, and higher levels of exchangeable aluminum than other soils.
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