CO
2 emissions are one of the greenhouse gases that significantly contribute to climate change. The use of reduced soil tillage practices could contribute to the mitigation of CO
2 emissions from soils under ongoing climate change conditions. The use of reduced and no-tillage practices in the summer period, the most critical period for CO
2 and for water loss from soils, would contribute to the mitigation of CO
2 emissions that is required by the European Union. The aim of this research was to contribute to the specification of CO
2 emission factors, following different soil tillage practices in the summer period under variations in weather. Gentler tillage practices were defined in terms of reducing CO
2 emissions from the soil. This research was carried out as a long-term field experiment. The effects of soil tillage practices on CO
2 emissions were studied over a six-year period as a long-term field experiment and concerned the use of different soil tillage practices for over 20 years (established in 1995), with these including conventional tillage (CT; plowing to 20–22 cm), reduced tillage (RT; chiseling to 10 cm), and no-tillage (NT; without tillage). The crop rotation was winter wheat–winter oilseed rape–winter wheat–pea. CO
2 emissions were measured at least 7–10 times during the summer–autumn period in the years 2017–2022 after agrotechnical operations following the winter wheat harvest. Soil moisture was determined in all the treatments. Weather conditions were measured by means of the meteorological station of the Crop Research Institute. The CO
2 emissions were the highest in the summer period under CT in comparison with RT and NT. Reduced tillage and no-tillage practices, with mulch on the surface of the soil, decreased CO
2 emissions by a 6-year average of 45% and 51%, respectively. The mean CO
2 emissions were 6.1, 3.1, and 2.9 μmol CO
2 m
−2 s
−1 for CT, RT, and NT. The highest CO
2 emissions and the largest differences among different tillage practices were measured in 2019, with high temperatures and repeated rainfall. CO
2 emissions under CT reached 22 μmol CO
2 m
−2 s
−1, which was 7.5 and 5.8 times higher than under RT and NT, respectively. Current weather conditions, mainly temperature and precipitation, played an important role in CO
2 emissions. The hot and dry weather in 2018 decreased overall CO
2 emissions, with CO
2 emissions, even under conventional tillage, reaching only 2.5 μmol CO
2 m
−2 s
−1 on average. As a result of climate change, the temperatures also gradually increased in the later stages of the year, with more summer days being expected during autumn and higher CO
2 emissions from soils being expected as a result.
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