Background: Antibiotics are widely used to treat animals from infections. After fertilizing, antibacterials can remain in the soil while adversely affecting the soil microorganisms. The concentration of oxytetracycline (OTC) in the soil and its effect on the soil microbial community was assessed. To assess the impact of OTC on the soil microbial community, it was added to the soil at concentrations of 50, 150, and 300 mg kg^–1 and incubated for 35 days. Results: The concentration of OTC added to the soil decreased from 150 to 7.6 mg kg^–1 during 30 days of incubation, as revealed by LC-MS. The deviations from the control values in the level of substrate-induced respiration on the 5th day of the experiment were, on average, 26, 68, and 90%, with OTC concentrations at 50, 150, and 300 mg kg^–1, respectively. In samples with 150 and 300 mg kg^–1 of OTC, the number of bacteria from the 3rd to 14th day was 2–3 orders of magnitude lower than in the control. The addition of OTC did not affect the fungal counts in samples except on the 7th and 14th days for the 150 and 300 mg kg^–1 contaminated samples. Genes tet(M) and tet(X) were found in samples containing 50, 150, and 300 mg kg^–1 OTC, with no significant differences in the number of copies of tet(M) and tet(X) genes from the OTC concentration. Conclusions: Our results showed that even after a decrease in antibiotic availability, its influence on the soil microbial community remains.

Antibiotics enter the soil with compost prepared from livestock manures and other sources. There is concern that they may influence plant growth and cause antibiotic resistance in soil and plant endospheric microbiomes. In the present work, lettuce plants were cultivated in soil and hydroponics spiked with oxytetracycline (0, 15, and 300 mg × kg⁻¹ and 0, 15, and 50 mg × L^–1, respectively) during a 28-day greenhouse experiment. It was revealed that the antibiotic reduced the chlorophyll content, the biomass, and the length of the roots and stems by 1.4–4.7, 1.8–39, 2.5–3.2, and 1.8–6.3 times in soil and in hydroponics. The copy numbers of the tet(A) and tet(X) genes were revealed to be 4.51 × 10³–1.58 × 10⁵ and 8.36 × 10⁶–1.07 × 10⁸ copies × g^–1, respectively, suggesting the potential migration of these genes from soil/hydroponics to plant roots and leaves. According to a non-metric multidimensional scaling (NMDS) analysis of the 16S rRNA amplicon sequencing data, endospheric bacterial communities were similar in leaves and roots independent of the growing substrate and antibiotic concentration. While soil bacterial communities were unaffected by the presence of antibiotics, hydroponic communities exhibited dependency, likely attributable to the absence of the mitigating effect of soil particle absorption.

One way to increase yields in agriculture using organic alternative methods is the introduction of manure-based composts into the soil. However, the use of such composts carries a risk of soil contamination with antibiotic resistance genes (ARG) from the gut and manure of the livestock. The contamination of the composts with heavy metals or antibiotics can increase this risk, while the addition of porous materials, such as biochar, to the composts has the potential to decrease it. This study is devoted to revealing the fate of ARGs in bedding chicken manure composted with the addition of oxytetracycline (OTC), heavy metals, and chicken manure biochar. It was revealed that the additives did not affect the physicochemical parameters of the compost. The bacterial communities in different composting mixtures had similar structures and dynamics. It was revealed that the shifts of the bacterial compositions of the composting mixtures were mainly determined by the duration of the process. However, some minor differences in the OTU (operational taxonomic unit) levels were observed between the variants. The addition of biochar and metals led to 26.7% and 34.5% decreases, respectively, in the number of tet(A) gene copies, while the addition of oxytetracycline led to a 43.7% increase. The number of copies of the int1 gene increased by 45.9% after the addition of oxytetracycline. The correlation between the abundance levels of different bacterial OTU and ARG contents was estimated, and biochar’s impact on those OTUs was analyzed. It was assumed that some OTUs might be carriers of ARGs (such as Natronobacillus, Luteimonas, and Trichococcus), and their abundance in the presence of the biochar decreased due to competitive exclusion by noncarriers (such as Corynebacterium, Clostridia, and Halorhodospira). The use of biochar in composting can be considered a way to reduce the contamination of the final composts with ARGs.

The aim of the research is to evaluate the impact of cover crops on CO2 emissions into the atmosphere by calculating the carbon footprint during the cultivation of white mustard (Sinapis alba L.) and oilseed radish (Raphanus sativus var. oleiferus), followed by incorporating the biomass into the soil. The study was conducted at the experimental field of the Agrobiotechnology park of Kazan State Agrarian University in the village of Narmonka, Laishevsky District, Kazan, from May to September 2023. The soil at the experimental site is gray forest soil, sandy loam in texture. The field experiment included growing cover crops followed by incorporating the biomass into the soil using three methods: traditional plowing, disking, and mowing without soil treatment. The total CO2 emissions from soil respiratory activity in plots with white mustard during mowing, disking, and plowing over the growing season amounted to 361, 469, and 674 kg CO2/ha, respectively; while for oilseed radish under the same treatments, emissions were 368, 501, and 684 kg CO2/ha. The total CO2 emissions from agricultural practices ranged from 93 to 130 kg CO2/ha depending on the last treatment method used. The CO2 captured in plant biomass significantly differed depending on the crop type: for white mustard, it was 18.605 kg CO2/ha; for oilseed radish, it was 10.560 kg CO2/ha. The calculated carbon balance showed that the difference in carbon dioxide emissions (∆CO2) when mowing white mustard was -18.145 kg/ha; for disking -18.004 kg/ha; and for plowing -17.791 kg/ha. For oilseed radish, lower values were established: -10.107 kg/ha; -9.991 kg/ha; and -9.756 kg/ha, respectively. Growing white mustard is an effective method for capturing carbon from atmospheric air. The carbon balance is most influenced by the amount of carbon captured in plant biomass and the agricultural practices applied.