Characteristics of Wheat Grown with Sewage Sludge Placed at Different Soil Depths
1980
Kirkham, M. B.
This study was done to determine the effect on plant growth and elemental uptake when sludge was applied in a layer below the surface rather than on the surface. Sludge was placed at different depths in columns of a clay loam soil (Udertic Paleustolls). Winter wheat (Triticum aestivum L. em. Thell. ‘Ponca’) was grown in the columns. When sludge was placed at the 0- to 2-cm depth (surface application), dry weight of shoots was 2.4 times more than when sludge was placed at the 18- to 20-cm depth. Root growth was prolific in the vicinity of sludge layers at the 18- to 20-cm depth, but total root weight in columns was about the same with sludge placed at either depth. Soil water content was lower in columns with better plant growth, probably because of greater transpiration. Dilute-acid (0.05N HCl + 0.25N H₂SO₄) extractable concentrations of heavy metals (Zn, Cu, Cd) in soil were lower when sludge was at the 18- to 20-cm depth than when sludge was at the 0- to 2-cm depth. Concentrations of Cu and Cd were highest in shoots of plants in columns with surface-applied sludge. Highest concentrations of Cu and Cd in the roots occurred when sludge was at the 18- to 20-cm depth rather than at the surface. Relatively small concentrations of Cu and Cd in roots were transferred to the shoots. The results showed that for maximum dry matter production, sludge should be surface-applied. For minimal transfer of heavy metals from roots to shoots, sludge should be layered below the surface of the soil.
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