Impact of crops and fertilizers on soil respiration in a long-term field experiment

Field experiments enable researchers to investigate the impacts of both natural and anthropogenic crop production factors on soil respiration (SR), the largest contributor of CO 2 emissions from terrestrial ecosystems to the atmosphere. The hypothesis of this study was that the influence of two key anthropogenic factors — applied fertilizers and cultivated crops — on the respiration rate of arable soils could be separated in a field experiment. The objective was therefore to quantify the influence of these factors on SR and assess its dependence on soil characteristics. The study was conducted on the territory of the long-term field experiment at the Timiryazev Academy (Moscow, Russia), where use of plots of crop rotation involving rye, barley, potatoes, and fallow, with liming and various fertilizer types applied, was considered. Measurements were taken using the closed chamber technique and a portable infrared gas analyzer from May 2023 to November 2024. During the vegetation periods SR varied significantly and was not statistically different for most plots (0.063‒0.276 g C/(m 2 ·h)), except for the NPK+manure variant (0.371‒0.430 g C/(m 2 ·h)). During the bare soil period SR was similar between fertilizer variants and 10‒20 times lower under snow cover than during the vegetation period (0.006‒0.018 g C/(m 2 ·h)). A direct dependence of respiration on soil organic carbon and particulate organic matter content was observed ( R =0.552‒0.650). Two-way PERMANOVA revealed significant effects of fertilizers (17.2‒24.0% of the variance) and crops (6.5‒7.1%) on SR, although their interaction was insignificant. Our research could form the basis for developing carbon sequestration compensation measures in response to specific fertilizer doses.