|Abstract or Summary
- Field and greenhouse experiments were conducted to determine the suitability of using incinerated sewage sludge ash as a soil amendment for sweet corn production on Willamette silt loam. In 1977, field plots were treated with 0, 11, 22, and 43 mt/ha of ash containing lime, in factorial combination with a P fertilizer variable (0 or 90 kg/ha P). In 1978, additional ash containing alum was applied to P fertilized plots only, resulting in cumulative ash rates of 27, 53, and 106 mt/ha. Sweet corn was grown both years and NH₄NO₃ and NH₄ SO₄ fertilizer was applied to provide N. Ash samples contained between 9 and 18% P₂0₅ and from 2 to 34% CaCO₃ equivalence. Elements assayed for in the waste and found in excess of 1% included Ca, P, Fe, and Al. Metals found in concentrations ranging from 0.1 to 1% were Mg, K, Na, Zn, Pb, Mn, Cu, and Cr; while Ni, B, Cd, and Mo concentrations were less than 300 µg/g. Soil pH increased from 5.3 to 6.0 with the highest ash application. Exchangeable Ca and available P; total P, Zn, Cd, Cu, Ni, Pb, and Cr; and DTPA-extractable Zn, Cd, Cu, and Pb content of the surface soil (0-15 cm) increased with ash applications. DTPA-extractable Mn decreased with waste addition while extractable Ni and Cr, and exchangeable Mg, K, and Na were not measurably affected. Water extracted a small portion (<0.5%) of the total Zn, Cd, Cu, Ni, Cr, and Pb in the surface soil and no trace metal movement below the 30 cm soil depth was detected, suggesting trace metal enrichment in the soil did not represent a source of groundwater contamination. Silage and mature ear yield increased in 1978 from 65 and 13 mt/ha, respectively, on the P fertilized control soil, to 78 and 17 mt/ha, respectively, when 106 mt/ha of ash was applied. Mature ear yield and leaf P content increased both with ash application and with P fertilizer treatments, suggesting a P response from the ash additions. The corn tissues contained a normal content of the elements assayed on both control and waste-treated soil. The Zn, Ca, Mg, P, B, and possibly Mo concentration in the leaves increased, while K and Mn contents decreased, with waste application. The Cd content of the leaves increased slightly with ash application in 1977 (from 0.26 to 0.35 µg/g) but not in 1978. The Cu, Cr, Pb, Na, and Ni concentration in the leaves and most elements assayed in the kernels and silage were largely unaffected by ash applications. In a greenhouse experiment, corn was grown on two pure ashes (low and high in water extractable Cr) and on Willamette soil amended with the ashes at rates which applied 0, 280, 560, 1120, and 2240 kg/ha of Zn. All pots received 56 kg/ha/week of N applied as NH₄NO₃ and NH₄SO₄. Corn grown on the ash which contained 12.5 µg/g of water extractable Cr was severely stunted and chlorotic, while corn plants grown on pure ash with only 0.054 µg/g of extractable Cr grew comparably to plants grown on control soils. If Cr toxicity was the cause of poor growth on the ash high in water extractable Cr, the problem was ameliorated when ash was mixed with soil, since corn plant yield on soil amended with either ash exceeded plant yield on the P fertilized control soil. Plant yields were greatest when ash was applied at rates which approximated the maximum allowable Zn addition (560 kg/ha), suggesting that for optimum corn growth, ash applications could be regulated by the USEPA (1977) guidelines for Zn addition. Utilization of incinerated sewage sludge ash as a soil amendment for sweet corn production on Willamette silt loam was a feasible waste management alternative.