Influence of Direct Seeding Technology on Respiration of Chernozem-Like Soils of Amur Region

Soil CO emission was measured by the field chamber method in the experiment on application of no-till technology (without tillage) on chernozem soils of the Amur region of Russia, where 30% of the country’s soybeans are grown. One-factor and two-factor models for estimation of soil respiration per year were constructed based on the data of field measurements for 2022-2024. Soil temperature is a reasonably good predictor of emission (R = 0.8, p < 0.001), which allows us to use continuous soil temperature series from loggers to calculate seasonal fluxes at a frequency of 6 times per day. Total annual flux in the experimental plot (no-till) was 0.69 t C/ha or 23.6% lower than in the control plot (conventional tillage). The contribution of the summer period to the annual flux was 59%. The two-factor T&P-model (temperature and precipitation) showed an overestimation of annual flux by 40%. Application of air temperature from the nearest weather station for modeling gave an underestimation of total flux by 13-20%. The no-till plot showed higher water-soluble carbon (2.5 and 3.8%, p = 0.055) and nitrogen (0.3 and 0.6%, p = 0.0025) relative to the conventional plot. Switching to no-till technology increases the density of the upper soil horizons by 8-12%, but the density remains within the optimum for soybean. In the no-till plot, soil volumetric moisture is also consistently higher (by 38% on average in the 0-5 cm layer), which is a strategically important advantage due to frequent periods of moisture deficiency.