Energy and Environmental Assessment of Bacteria-Inoculated Mineral Fertilizer Used in Spring Barley Cultivation Technologies

In the scientific literature there is a lack of information on the integrated effect of bioenriched complex mineral fertilizers in the energy and environmental aspects of spring barley production technology. The aim of this study was to validate the type of phosphorus-releasing bacteria and to carry out an energy and environmental assessment of the use of mineral fertilizers enriched with them for barley fertilization. The experimental field studies (2020-2022) were carried out in open ground on sandy loam soil in southern Lithuania. Four barley cultivation technologies (SC) were applied. Control (SC-1) did not use complex mineral fertilizers; in SC-2, 300 kg ha-1 of N5P20.5K36 fertilizer was applied. In SC-3, the same fertilizer was enriched with a bacterial inoculant (Paenibacillus azotofixans, Bacillus megaterium, Bacillus mucilaginosus, and Bacillus mycoides) at a rate of 150 kg ha-1, and in SC-4, 300 kg ha-1 of N5P20.5K36 fertilizer were applied and the same enrichment with the bacterial inoculant was carried out. The results confirmed the hypothesis that spring barley cultivation technologies using bacterial inoculants (SC-3 and SC-4) have higher mineral fertilizer efficiency than SC-2. In all three years, the bacterial inoculant had a positive effect on phosphorus fertilizer efficiency. In SC-4 (2020) it was 8%, in 2021-7%, and in 2022-even 17% higher compared to SC-2. In terms of energy balance, a significant influence of the bacterial inoculant was found. In 2020 and 2021, the energy balance of SC-4 was 10%, and in 2022, 22.8% higher compared to SC-2. The increase in fertilizer use efficiency resulted in a positive environmental impact, with greenhouse gas (GHG) emissions decreasing by 10% in 2020, 15% in 2021, and 19% in 2022 when comparing SC-4 and SC-2. The use of the tested bacterial formulations, without changing the mineral fertilizer rate, can lead to an average reduction in GHG emissions of about 15%. This study demonstrates that enriching mineral fertilizers with specific bacterial inoculants for spring barley cultivation significantly enhances phosphorus efficiency, improves energy balance, and reduces greenhouse gas emissions, underscoring the potential for bioaugmented fertilizers to optimize agricultural sustainability.