Effect of soil supplementation with mineral-organic mixtures on the amount of maize biomass and the mobility of trace elements in soil

Abstract

The application of calcium fertilisers and organic fertilisers or materials is an alternative allowing to reduce soil acidification and increase the organic matter content. Under Polish conditions, where soils belonging to the agronomic category of light and acidic soils predominate, such an approach can bring measurable benefits in improving physical, chemical, and biological properties of soils. However, it should be noted that until now these treatments have usually been applied separately; therefore, the aim of this study was to determine the effect of the combined application of calcium carbonate fertiliser with leonardite (CaLO) and with poultry litter (CaPL) on the amount of maize biomass, the content of trace elements in the biomass, and selected soil properties, including the mobility of trace elements in soil. The study was conducted as a pot experiment. The experimental design included 4 treatments: soil with no fertilisers (Control), soil with mineral fertilisers (NPKS), and soil with mineral fertilisers and the addition of a mixture of CaCO3 and leonardite (NPKS+CaLO) as well as CaCO3 and poultry litter (NPKS+CaPL). The study showed a substantial increase in the amount of mainly aboveground parts of maize biomass after applying mixtures of CaCO3 and organic materials. Despite the lack of significant differences, the relative increase in the chlorophyll a content in NPKS+CaLO and NPKS+CaPL treatments was over 7 % compared to NPKS treatment. The obtained results are inconclusive as to the effect of the applied mixtures on the trace element content in maize biomass. Soil supplementation with CaLO mixture significantly reduced cadmium, copper, and lead contents in maize aboveground parts, while the zinc content was higher compared to the NPKS-fertilised treatment. Soil supplementation with CaPL mixture decreased the zinc content in maize aboveground parts, while the cadmium, copper, and lead contents were higher compared to the NPKS-fertilised treatment. Soil pH significantly improved after applying CaLO and CaPL mixtures. Soil supplementation with CaLO and CaPL was vital for reducing the content of water-soluble forms of Cd and Zn, while for Pb and Cu, we observed an increase in these forms of trace elements in the soil. The treatments with CaLO and CaPL had lower content of NH4EDTA-extracted elements compared to the control.