Plant availability of phosphorus and cadmium in soil amended with waste materials

The aim of fertilisation is to improve the quantity and quality of crops while preservingthe used soil. Several products from waste materials are believed to meet these necessities.To verify this statement, Biosolids, Biosolid ashes and mixtures of Biosolidswith fly ash from incineration processes are investigated. Especially their influence onplant available phosphorus and cadmium are of interest.A laboratory-scale plant experiment was carried out. The scope was to determine theinfluence of different waste materials on certain properties: the quality and quantityof the vegetation and the chemistry of the soil and the soil pore water. Excludingthe control samples, 55 pots were amended with 20 different fertilisers. In all potsgrass was used as vegetation. At both the beginning and the end of the experimentwere pore water samples taken. Afterwards, the plant shoots were cut and several soilsamples collected. The chemical composition of all these materials was investigated.Additionally the dry matter of the plant shoots was determined.The results for the proposed fertilisers vary. Changes found in most of the pore watersamples were rather positive: slightly increased pH-values and increased contents ofphosphates. However, this did not reflect on the plant growth. The plants grown in soilcontaining Biosolids developed low biomass, a maximum of approx. 9.0 g/m². Whereasplants grown in pots with Biosolid ashes produced the highest biomass: > 20.0 g/m².Considerable changes of the assessed parameters were only displayed by the mixtureof Biosoldis and fly ash from waste incineration. The amount of cadmium in the plants,the soil and its pore water was very high.All in all, only several Biosolid ashes should be further regarded as potential fertilisers.Biosolids are suggested for an alternative way of application, concerning theirmostly positive influence on the soil pore water. The usage of the leftover ashes fromBiosolids and the mixtures of Biosolids and fly ashes need further studies to clarifytheir potential to be used as fertilisers.Validerat; 20130827 (global_studentproject_submitter