Composition of Organic Fertilizers Containing Microorganisms and Their Effect on Soil Microbiological Activity and Plant Growth

The conversion of livestock manure and peat into value-added fertilizers provides an environmentally sustainable approach to nutrient recycling and waste management. In this study, organic fertilizers were formulated from poultry, pig, and cattle manure mixed with peat and wood ash, with or without inoculation of the phosphate-solubilizing bacterium Priestia megaterium. Their efficiency was evaluated through plant growth and soil microbiological experiments involving conifer seedlings, herbaceous crops, and ornamental plants. Germination and growth trials with Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) revealed clear species-specific responses: spruce seedlings performed best in substrates containing poultry or cattle manure, while pine showed enhanced growth with pig manure combined with bacterial inoculant. In pansies (Viola × wittrockiana), growth responses varied by cultivar; cattle manure enriched with bacteria increased leaf projection area, whereas poultry manure markedly suppressed growth. For cucumbers, basil, barley, radish, and garden beans, yields were lower than with mineral fertilizers, yet bacterial inoculation significantly influenced soil microbial activity by modifying respiration rates and hydrolytic enzyme intensity in plant- and manure-specific ways. The results demonstrate that microbial supplementation can alter soil biological processes and nutrient turnover, though its effects on plant productivity remain inconsistent. Further research is required to assess long-term performance under field conditions, as practical application will depend on achieving stable and reproducible results.