Author: D. B. Cohen

Publisher:

Published: 1977

Total Pages: 152

ISBN-13:

Lysimeter experiments in which crops were grown on agricultural soils treated with anaerobically digested sewage sludges (from plants where phosphorus removal was being practised using metal salts) were initiated in 1972 and 1973. Alum, iron and lime treated fluid sludges were added to loamy sand and silt loam soils vegetated with orchard grass. Similarly, alum, iron and lime treated air-dried sludges were added to sand and clay soils and wheat crops were grown. The high application rates of fluid and air-dried sludges ranged From 32 to 76 and 47 to 144 tons dry wt/ha/yr, respectively. The metal loadings approximated the recommended maxima for Ontario agricultural land. The lower rates were one-third and two-thirds of the high rates. The results of these experiments are presented and compared to results from field and greenhouse studies. There was no evidence that the aluminum, iron or lime in the digested sludges was detrimental to crop production or plant tissue quality. Orchard grass yields from the f1uid sludge experiment appeared to be related to nitrogen avai1abi1ity. Ìn general t land application of sewage sludges at rates sufficient to supply the crop uptake of N and P would limit soil heavy metal loadings to acceptable levels for the sludges used in these lysimeter studies.