CO2 Emission from Soil as a Result of Short-Term Green Manuring of Fallow Fields in the Cis-Baikal Forest-Steppe Zone

摘要

The focus of modern agricultural production on reducing greenhouse gas emissions requires attention to newly introduced farming practices, in particular from the standpoint of their influence on CO2 fluxes. Specific features of CO2 emission from soil as a result of short-term summer green manuring of fallow fields (during 35-40 days from sowing to plowing into the soil of Raphanus sativus var. oleifera Metzg) have been studied. This is a non-standard farming practice used in the forest-steppe zone of the Cis-Baikal Region. Changes in the seasonal dynamics of the CO2 emission relative to the traditional black fallow were studied in three-year (2015-2017) field experiments on gray forest silt loamy soil. An increase in the intensity of CO2 emission from the soil surface after the green mass is plowed into the soil was shown for two crop rotations. The total (May-September) CO2 efflux from the soil in the variant with green manure was 1.3-1.6 times higher than that from the traditionally cultivated soil in all years of the experiment. The intensity of mineralization processes on the plots with green manure enhanced by 38-131 in comparison with that in the black fallow. The loss of carbon reached 19-79 of the amount accumulated in the net primary production. The range of fluctuations in the total CO2 efflux from the soil depended on a combination of factors: hydrothermic conditions, the C-org and N-tot content in soil; the C-to-N ratio, the N and water contents in tissues of green manure, and the carbon stock in root and aboveground residues of the precursor. The correlation between the CO2 efflux and the studied factors weakened in the following sequence: qualitative characteristics of the green mass of oil radish > initial soil fertility > carbon pool in residues of the precursor. The results obtained indicate that the application of green manure to the fallow field increases the CO2 emission from gray forest soil during the warm season.