ANALYSIS OF THE GROWTH AND METABOLIC ACTIVITY OF MICROORGANISMS IN SUBSTRATES PREPARED ON THE BASE OF SEWAGE SLUDGES AND THEIR IMPACT ON GROWTH AND FLOWERING OF GARDEN VERBENA

摘要

The study presents the microbiological and biochemical characterisation of peat substrates supplemented with composts manufactured from sewage sludge, maize, lupine and wheat straw under cultivation of garden verbena. At three successive plant developmental stages, substrate samples were collected and subsequently analysed micro-biologically and biochemically. The performed microbiological analyses involved determination, using the Koch plate method, of total numbers of heterotrophic bacteria, actinomycetes and molds. The experimental substrates were also subjected to biochemical analyses which involved spectrophotometric determination of levels of dehydrogenase activity. In addition, the following plant morphological analyses were performed: plant height, shoot number and length, number of buds, inflorescences and leaf greenness index (SPAD). It was found that the plants cultivated on peat substrate, with addition of various composts, grew properly and their appearance did not differ from plants grown on a traditional peat substrate. It was further found that the addition of some composts (especially K3 made up of sewage sludge, rape straw and sawdust) to the peat made it possible to obtain higher plants, and stimulated the development of inflorescence buds. On the other hand, majority of the employed composts failed to exert a stimulatory effect on the greenness index of plants, or the number of developed inflorescences. It was observed that, irrespective of the kind and dose, the applied composts following their addition into peat contributed most to the stimulation of actinomycetes, molds development and dehydrogenases activity, but to a lesser degree, the development of heterotrophic bacteria. Among major factors determining substrate enzymatic activity as well as changes in numbers of the investigated microorganisms were substrate pH value as well as the developmental phase of garden verbena.