Growth of tulips treated with sludge containing dewatering chemicals

Abstract

Tulips were grown for 56 days in pots with a greenhouse medium containing a ferric chloride-lime treated, dewatered sludge called chemical sludge. Growth was compared with that of tulips receiving dried organic sludge, liquid organic sludge, primary effluent or tap water, to make a total of five treatments. The organic sludge, dried and liquid, had no chemicals added. It was either incorporated in a dried form into the medium or added in a liquid form to the surface. Average height of plants, in millimetres, at the end of the experiment for the five treatments was chemical sludge, 120; dried organic sludge, 192; liquid organic sludge, 466; effluent, 463 and water, 460. Extractable concentrations of Fe and Cl were no higher in the medium treated with the chemical sludge than in that treated with dried or liquid organic sludge. Electrical conductivities and extractable concentrations of Ca were 1·4 and 1·6 times higher, respectively, and extractable concentrations of Cu, Fe, K, P and Zn, 5·9, 2·6, 3·3, 2·8 and 1·8 times lower, respectively, in the medium treated with the chemical sludge than in that treated with the dried organic sludge. The results showed that the lime added to condition sludge at the sewage treatment plant reduced trace element, K and P availability.