Soil Organic Carbon Sequestration and Distribution, Soil Biological Characteristics, and Winter Wheat Yields Under Different Tillage Practices in Long-Term Field Experiment

The organic carbon content of soil (SOC) is considered a key factor for soil health and plays an important role in climate change. Conservation tillage systems promote carbon sequestration and reduce greenhouse gas emissions. A long-term field experiment with different soil tillage practices (conventional tillage—CT; reduced tillage—RT; and no tillage—NT) has been conducted in Prague-Ruzyně (Czech Republic) since 1995. The soil’s organic carbon content, microbial biomass (Cmic), and enzymatic characteristics were evaluated in four-year crop rotation periods from 2005 to 2024. The crop rotation was as follows: winter oil seed rape, winter wheat, pea, and winter wheat. The following soil layers were studied: 0–10, 10–20, and 20–30 cm. Crop residues remained in the field and were incorporated into the soil according to the used tillage—completely under CT, partly under RT, and the remaining mulch under NT. Under RT and NT, the SOC, Cmic, and enzymatic activity were concentrated in the top soil layer and decreased in deeper layers, whereas all these characteristics were evenly distributed across the soil layers under the CT practice. The SOC content increased gradually in the whole soil profile (0–30 cm) from 51.0 t ha−1 on average in 2005–2008 to 56.0 t ha−1 in 2021–2024 under CT. An SOC increase from 57.4 to 63.1 t ha−1 under RT and from 61.1 to 65.7 t ha−1 under NT was noted in 2017–2020, after which the stagnation in SOC content was observed in the years of 2021–2024. Similarly, a lower Cmic and enzymatic activity were found in the same period. The highest C sequestration was found under NT; an increase of 571 kg C ha−1 year−1 was recorded from the establishment of the experiment in 1995 to 2024. This was followed by the RT and CT practices (462 and 221 kg C ha−1 year−1, respectively). The average winter wheat yields and nitrogen content in grain were higher under CT (8.67 t ha−1, 2.16% N) and RT (8.97 t ha−1, 2.13% N) than under NT (8.23 t ha−1, 2.03% N). The weather conditions during the year (abundance of precipitation) influenced crop yields significantly more than the tillage practices. Conservation tillage practices increase the organic carbon and microbial activity in soils, but climate change associated with higher average temperatures can affect these processes.