The use of aerobic and anaerobic sewage sludges as organic fertilisers in lettuce (Lactuca sativa L.) var. vanity.

摘要

The objective of this work is to study aerobic (SSa) and anaerobic sewage sludges application (SSan) in lettuce (Lactuca sativa L.) production. Experimental pots were placed in randomized design and filled with Calcic Luvisol (LVk), according to theFAO-UNESCO Soil Classification; its pH was 8.7; organic matter content was 2.43; total N, available P and available K soil contents were, respectively, 3100 mg kg-1; 200 mg kg-1; and 400 mg kg-1. Increasing amounts of SSa, SSan and an inorganic fertilisers (IF) were added in the pots, according to four nitrogen (N) fertilisation: X/2; X; 2X; and 4X, where X=0.338 g N. Yield and plant heights were evaluated. Several plant nutrients were determined: nitrogen (N), phosphorous (P), calcium (Ca) and zinc (Zn). Heavy metals, such as cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb) were also analysed. Several parameters were determined after the experiment: pH, electrical conductivity (EC), organic matter content (OM), nitrogen (N), available phosphorous (P2O5), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb). Spores of Clostridia were analysed in soil samples. They were not detected in lettuce, but they were present in soil samples fertilised with both sewage sludge andthe inorganic fertiliser. The data were statistically analysed by ANOVA and comparative analyses of the means were performed by Duncan test using the SPSS Programme.