Influence of dried digested sewage sludge on yield and element composition of lucerne

Open Access
Publisher Website
Google Scholar
Abstract
Pot trials, in which dried digested sewage sludge from the Levin Treatment Station was applied to two soils, have shown that the treatments improved the growth of lucerne and induced changes in its element composition. Topsoils used in the trial were a horticultural soil, Levin silt loam (integrade between yellow-brown earth and yellow-brown loam), and a soil under exotic forest, Waitarere sand (yellow-brown sand). Sludge was applied in two ways, either mixed in with the soil or spread as a surface layer. Mixing in showed more statistically significant relationships than layering, and only the mixing in treatment is reported. Analysis of the dried digested sludge from Levin for 27 elements showed that its heavy metal content was much lower than that of sludges from highly industrial cities. The effect noted in element composition of lucerne was potassium deficiency and not toxicity by heavy metals. Histograms and statistical appraisal show the patterns of element uptake over seven harvest cuts for different proportions of sludge added to the soils.