Nutrient Management Drives the Direction and Magnitude of Nitrous Oxide Flux in Crop Residue-Returned Soil Under Different Soil Moisture

• Published in: Frontiers in environmental science 2022-03, Vol.10
• Main Authors: Lenka, Sangeeta, Choudhary, Rajesh, Lenka, Narendra Kumar, Saha, Jayant Kumar, Amat, Dolamani, Patra, Ashok Kumar, Gami, Vijay, Singh, Dharmendra
• Format: Article
• Language: English
• Subjects: C:N ratio; climate change; CO2 flux; greenhouse gas; residue quality; soil respiration
• ISSN: 2296-665X; 2296-665X
• DOI: 10.3389/fenvs.2022.857233

Crop residues as key organic carbon inputs have the potential for soil carbon sequestration. However, previous studies have shown an inconsistent effect of residue return on the direction and magnitude of soil nitrous oxide (N 2 O) emission. We used a laboratory-based soil incubation study to test the response of N 2 O emission to crop residue type, soil moisture, and how nutrient management modulates these responses. In this study, we incorporated crop residues with different qualities (wheat, rice, soybean, and maize) at two soil moisture contents {80% field capacity (FC) and 60% FC} and under seven nutrient levels: N0P0K0 (no nutrients), N0PK, N100PK, N150PK, N100PK + manure@ 5 Mg ha −1 , N100PK + biochar@ 5 Mg ha −1 , and N150PK + biochar@ 5 Mg ha −1 . The results demonstrated significant ( p < 0.01) differences in the magnitude of N 2 O emissions among treatments. However, only the interaction effect of residue × nutrient and nutrient × moisture was significant ( p < 0.05). N100PK and N150PK at 80% FC mitigated N 2 O emission by approximately 20% in wheat residue-amended soil ( cf . control soil without residue). In contrast, maize residue amendment ( cf. control soil) increased N 2 O emission by 130% under N0P0K0 and 80% FC. Residue effects were negatively correlated with the C:N ratio, and a strong positive correlation ( p < 0.01) was obtained between N 2 O emission and CO 2 respiration, labile carbon, mineral N, and residue total nitrogen (TN). When no nutrients were added, N 2 O emission was higher in residue returned soil. However, cumulative fluxes of N 2 O decreased by 6–17% when maize and wheat residues ( cf. control soil) were applied with nutrients. Negative fluxes of N 2 O indicating consumption were observed in every treatment after 57 days of incubation and were most pronounced in control soil without residue and nutrients. Decreasing the soil moisture from 80% FC to 60% FC, the N 2 O consumption rate increased by 6.6 times across residue types and nutrient management. The regression analysis and structural equation modeling (SEM) results showed that residue TN, soil CO 2 emission, NO 3 -N, and labile SOC were the key predictor variables and could explain 82% variability in the soil N 2 O emission in the Vertisols of Central India. The results suggested that nutrient addition (NPK) could alter the magnitude and direction of soil N 2 O flux by residue type and soil moisture by influencing the underlying soil microbial processes of the C an