Various methods have been applied to utilize semicoke -a by-product of oil shale production -harmless for environment. Use of compost, manufactured with semicoke, as agricultural soil improvement substance, would be one of the options available. This paper is an attempt to assess the economic effect obtained by applying different compost mixtures to several horticultural crops: swede (Brassica napus), beetroot (Beta vulgaris) and strawberry (Fragaria x ananassa), using the gross margin calculation method. The following compost mixtures were used: recultivation substance and solid fraction of pig manure (1:2); recultivation substance and sewage sludge (1:2) and sewage sludge alone. Composts applied increased the yield of swede, beetroot and strawberry; positive after-effect of composts was notable also in the second year. Positive effect on gross margin became obvious only during the second year. Sewage sludge and compost mixed with recultivation substance was economically more expedient for swede cultivation while sewage sludge compost was more efficient for beetroot cultivation. As for strawberry cultivation, use of mixture of re-cultivation substance and solid fraction of pig manure seemed to be most effective.
In industrialized society, large amounts of oily sediments from contaminated sites as well as oily sludge from industrial processes need to be treated in sustainable way. Nowadays biological treatment is becoming more important. The purpose of biotreatment is to decrease the concentration of organic pollutants (e.g. oil) in soil or compost by mineralizing hazardous chemicals into harmless compounds such as carbon dioxide or some other gas or inorganic substance, water, and cell material. Whereas hydrocarbons are generally well degradable, some organic compounds (e.g. PAH) are less degradable; and some (heavy metals) can not be degraded. However, resistant compounds can be transformed through sorption, methylation, and complexation, and change in valence state, which affect mobility and bioavailability. The use of oil-compost depends on legislative limits, and response of vegetation. Oil-content may have a negative effect on plant root system even in low concentrations. Heavy metals may inhibit the growth, but in the other hand, the plants are also known in uptaking heavy metals and other contaminants, known as phytoremediation. This may create a situation, where vegetation cover acts as additional treatment system for matured oil-composts. The objective of this study was to examine the effect of hydrocarbon residues in different substances (compost and soil mixtures) on soil model plants (Raphanus sativus) germination and phytomass production. The germination study demonstrated that the plants germination and biomass production was highly dependent on compost decomposition degree, nutrient content and biological properties of soil. On less matured compost, the germination and growth was suppressed. The phytomass production experiment showed that plants in oil compost had decreased height, taproot mass and above ground phytomass. The application of complex mineral fertilizers increased the volume of abovementioned parameters.
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