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Incorporating crop residues into the soil is an effective method for improving soil carbon sequestration, fertility, and crop productivity. Such potential benefits, however, may be offset if residue addition leads to a substantial increase in soil greenhouse gas (GHG) emissions. This study aimed to quantify the effect of different crop residues with varying C/N ratios and different nitrogen (N) fertilizers on GHG emissions, yield, and yield-scaled emissions (GHGI) in winter wheat. The field experiment was conducted during the 2018–2019 winter wheat season, comprising of four residue treatments (no residue, maize residue, soybean residue, and maize-soybean mixed residue) and four fertilizer treatments (control, urea, manure, and manure + urea). The experiment followed a randomized split-plot design, with N treatments as the main plot factor and crop residue treatments as the sub-plot factor. Except for the control, all N treatments received 150 kg N ha−1 season−1. The results showed that soils from all treatments acted as a net source of N2O and CO2 fluxes but as a net sink of CH4 fluxes. Soybean residue significantly increased soil N2O emissions, while mixed residue had the lowest N2O emissions among the three residues. However, all residue amendments significantly increased soil CO2 emissions. Furthermore, soybean and mixed residues significantly increased grain yield by 24% and 21%, respectively, compared to no residue amendment. Both soybean and mixed residues reduced GHGI by 25% compared to maize residue. Additionally, the urea and manure + urea treatments exhibited higher N2O emissions among the N treatments, but they contributed to significantly higher grain yields and resulted in lower GHGI. Moreover, crop residue incorporation significantly altered soil N dynamics. In soybean residue-amended soil, both NH4+ and NO3− concentrations were significantly higher (p < 0.05). Conversely, soil NO3− content was notably lower in the maize-soybean mixed residue amendment. Overall, our findings contribute to a comprehensive understanding of how different residue additions from different cropping systems influence soil N dynamics and GHG emissions, offering valuable insights into effective agroecosystems management for long-term food security and soil sustainability while mitigating GHG emissions. [ABSTRACT FROM AUTHOR]

Purpose: The key environmentally beneficial process that substantially removes reactive nitrogen from biosphere is a complete denitrification. The science of measuring and constraining nitrous oxide (N2O) emissions has advanced significantly; however, despite several attempts, in situ dinitrogen (N2) measurement is still a great challenge and is poorly understood due to the high atmospheric N2 background. This study aimed at estimating field-scale inferred N2 emissions using data of field N2O emissions and laboratory-measured N2O/(N2O + N2) ratios and correlating those emissions with the soil-environmental factors. Materials and methods: Closed static chamber and He/O2 direct measurement methods were used at field and laboratory scale, respectively. For each treatment (varying N fertilizer rates), on each sampling date, N2O and N2 emissions were measured at laboratory and N2O emissions at field-scale, allowing the calculation of field-scale inferred N2 emissions. Results: The results demonstrate that field-scale inferred cumulative N2 emissions were 1.35, 1.48 and 1.60 times greater than laboratory-measured cumulative N2 emissions in low nitrogen level (LNL), medium nitrogen level (MNL) and high nitrogen level (HNL) treatments, respectively. This suggests that estimating N2 emissions at the field-scale in agricultural soil could give more insight on N cycling processes. Moreover, N fertilizer application rates increased linearly both field and laboratory cumulative N2O and N2 emissions. Both positive and negative relationships between soil-environmental parameters and N2O, N2 and their N2O/(N2O + N2) ratios at field and laboratory-based indicate their heterogeneous roles in N2O formation and reduction processes. Conclusion: The results provide complementary insights into field-scale N2 emissions in agricultural soil and help in closing the knowledge gap in the N balance. Linear relationships between the emissions (N2O and N2) and N fertilizer rates observed suggest that climate change mitigation options could be achieved by optimizing the N fertilization rates since N2O and N2 emissions are enhanced by increasing N inputs. As our results present the field-scale inferred N2 emissions, there is still a need to design a robust methodological approach that will enable researchers to directly quantify field N2 emissions. [ABSTRACT FROM AUTHOR]

Micro sensors have large potential to measure soil nitrous oxide (N2O) emissions. However, because of its low sensitivity to get the electrical signals on soil with low moisture content, little research has been conducted in semi-arid agro-ecosystem. Moreover, the use of N2O microelectrode studies were largely focused on the marshy fields, paddy fields and waste waters with high soil moisture content. In order to characterize the boundary of the sensor signal (upper and lower), purified water without N2O is usually used as the calibration medium to calibrate the electrode. However, the physical and chemical properties of purified water and soil leaching solutions are very different. In this study, we improved and verified a microelectrode calibration method based on selecting appropriate media and optimal electrolyte concentration. In addition, we applied the improved microelectrode calibration method to continuously observe N2O flux from the soil column in a 30-day-long incubation experiment. The results pointed to noteworthy improvement of the microelectrode calibration compared to the current method, with soil solution validated as a calibration medium at optimal electrolytic concentration of 7:1-8:1, expressed as water/soil ratio. The emission of N2O from soil with different soil fertility were also significantly different. Our research is beneficial to establish the microelectrode calibration method of N2O emission under low moisture conditions from soil microenvironment, and also points on management practices of agro-ecosystem for N2O mitigation strategies. [ABSTRACT FROM AUTHOR]

Optimum grafting time and grafting methods were found out through grafting research on Vietnamese lacquer tree for three years. The results showed that the survival rate was 48% in summer by side grafting and it was 88% in autumn, which was higher than the survival rate according to the corresponding literature. Thus, the survival rate of Vietnamese lacquer tree by side grafting could be greatly increased at autumn. [ABSTRACT FROM AUTHOR]