CO2 Emissions from Soils under Different Tillage Practices and Weather Conditions

CO2 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 CO2 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 CO2 and for water loss from soils, would contribute to the mitigation of CO2 emissions that is required by the European Union. The aim of this research was to contribute to the specification of CO2 emission factors, following different soil tillage practices in the summer period under variations in weather. Gentler tillage practices were defined in terms of reducing CO2 emissions from the soil. This research was carried out as a long-term field experiment. The effects of soil tillage practices on CO2 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. CO2 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 CO2 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 CO2 emissions by a 6-year average of 45% and 51%, respectively. The mean CO2 emissions were 6.1, 3.1, and 2.9 mu mol CO2 m(-2) s(-1) for CT, RT, and NT. The highest CO2 emissions and the largest differences among different tillage practices were measured in 2019, with high temperatures and repeated rainfall. CO2 emissions under CT reached 22 mu mol CO2 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 CO2 emissions. The hot and dry weather in 2018 decreased overall CO2 emissions, with CO2 emissions, even under conventional tillage, reaching only 2.5 mu mol CO2 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 CO2 emissions from soils being expected as a result.