Soil N2O emission intensity under different crop fertilization systems and the use of PGPR

Introduction This study evaluated the intensity of N 2 O emissions from a leached light-loam Chernozem (Phaeozem Chernic) during crop cultivation within a crop rotation potato -> spring barley -> pea -> winter wheat under various fertilization systems and the use of PGPR for pre-sowing seed treatment. The fertilization systems included: application of 5 t/ha of winter wheat straw; post-harvest cultivation of lupine green manure followed by biomass soil incorporation; combined application of straw and green manure; annual application of mineral fertilizers at low, medium, and high rates (N 40 P 40 K 40 , N 80 P 80 K 80 , and N 120 P 120 K 120 for potatoes; N 30 P 30 K 30 , N 60 P 60 K 60 , and N 90 P 90 K 90 for barley, peas, and wheat, respectively); and the application of corresponding fertilizer rates against backgrounds of direct action (under potato cultivation) and the residual effects of straw and green manure (under barley, pea, and wheat cultivation). Azospirillum brasilense IMV B-7222 was used to inoculate potato tubers and barley seeds; Rhizobium leguminosarum 348a was used for peas; and Paenibacillus polymyxa IMV B-8059 was used for wheat. Methods The study was conducted as part of a long-term field experiment established in 2009. The N2O flux was measured during 2019–2021 three times per growing season for each crop at different key developmental stages using closed static chambers and gas chromatography. Results Sole use of mineral fertilizers increased N 2 O emissions, which rose proportionally with increasing nitrogen rates. However, N 2 O emission intensity decreased by 7-12%, subject to the fertilizer application rate and potato growth stages, when mineral fertilizers were applied against the background of straw and lupine green manure. In the first year of the residual effect of these organic amendments (under barley cultivation), N 2 O loss intensity decreased by 6-13%; in the second year of the residual effect of straw and green manure (under pea cultivation), nitrous oxide emissions decreased by 10-18% across developmental stages compared to treatments where mineral fertilizers were applied alone. By the third year of the residual effect of straw and green manure (under winter wheat cultivation), their efficacy in mitigating nitrous oxide emissions diminished – differences compared to mineral-only treatments were either statistically non-significant or marginal. PGPR inoculation contributed to lower N 2 O emissions across all studied crops, including organo-mineral fertilization treatments. The most pronounced emission reduction, coupled with the highest crop yields, occurred in treatments combining mineral fertilizers, organic matter, and PGPR inoculation. Overall, integrating mineral fertilizers with wheat straw and lupine green manure, through both direct and residual effects, reduced N 2 O emission intensity compared to mineral fertilization used alone, while PGPR inoculation enhanced this mitigation. These findings confirm the viability of integrated nutrient management strategies that balance environmental sustainability with agricultural productivity.