Global integrative meta-analysis of the responses in soil organic carbon stock to biochar amendment.

Applying biochar to soil has been recognized as a promising practice of climate-smart agriculture, with considerable potential in enhancing soil organic carbon (SOC) sequestration. Previous studies showed that biochar-induced increases in SOC stock varied substantially among experiments, while the explanatory factors responsible for such variability are still not well assessed. Here, we conducted an integrative meta-analysis of the magnitude and efficiency of biochar-induced change in SOC stock, using a database including 476 field measurements at 101 sites across the globe. Biochar amendment increased SOC stock by 6.13 ± 1.62 (95% confidence interval, CI) and 7.01 ± 1.11 (95% CI) Mg C ha-1, respectively, compared to their unfertilized (R0) and mineral nitrogen (N) fertilized (Rn) references. Of which approx. 52% (R0) and 50% (Rn) were contributed directly by biochar-C input. Corresponding biochar carbon efficiencies in R0 and Rn datasets were estimated as 58.20 ± 10.37% and 65.58 ± 9.26% (95% CI), respectively. The change magnitude of SOC stock increased significantly (p < 0.01) with the increasing amount of biochar-C input, while carbon efficiency of biochar showed an opposite trend. Biochar amendment sequestered larger amounts of SOC with higher efficiency in acidic and loamy soils than in alkaline and sandy soils. Biochar amendments with higher C/N ratio caused higher SOC increase than those with lower C/N ratio. Random forest (RF) algorithm showed that accumulative biochar-C input, soil pH, and biochar C/N ratio were the three most-important factors regulating the SOC stock responses. Overall, these results suggest that applying high C/N ratio biochar in acidic soils is a recommendable agricultural practice from the perspective of enhancing organic carbon.

Understanding the viral shedding time of Omicron variant BA.2 infection in Shanghai: A population-based observational study.

Objectives: To explore the multifactorial causality of prolonged viral shedding time and identify different viral shedding trajectories in Omicron BA.2 variant infections. Methods: The Kaplan-Meier method was used to estimate the survivor function, and the Cox proportional hazards model was fitted to identify factors associated with viral shedding time. Group-based trajectory model (GBTM) was used to identify different viral shedding trajectories. Ordinal logistic regression was used to identify factors that significantly impacted the trajectory membership. Results: The overall median viral shedding time was 12 days (interquartile range [IQR]: 8-15). Viral shedding time was longer for female cases, cases who were incompletely vaccinated, cases with comorbidities, cases with severe or critical infections and cases who had not taken Paxlovid within 5 days after diagnosis. Compared to the 3 to 17-year-old group, all older groups had significantly longer viral shedding times. The GBTMs based on the N gene and the ORF1ab gene were consistent. Three viral shedding trajectories were identified and age group, comorbidities, vaccination status, disease state, Paxlovid treatment were significantly associated with the trajectory membership. Conclusion: Increased age, comorbidities, incomplete vaccination, severe or critical infections, and delayed Paxlovid treatment were the risk factors for prolonged viral shedding time.

Magnitude and efficiency of straw return in building up soil organic carbon: A global synthesis integrating the impacts of agricultural managements and environmental conditions.

Enhancing soil organic carbon (SOC) through straw return (SR) has been widely recommended as a promising practice of climate-smart agriculture. Many studies have investigated the relative effect of straw return on SOC content, while the magnitude and efficiency of straw return in building up SOC stock remain uncertain. Here, we present an integrative synthesis of the magnitude and efficiency of SR-induced SOC changes, using a database comprising 327 observations at 115 sites globally. Straw return increased SOC by 3.68 ± 0.69 (95 % Confidence Interval, CI) Mg C ha-1, with a corresponding C efficiency of 20.51 ± 9.58 % (95 % CI), of which <30 % was contributed directly by straw-C input. The magnitude of SR-induced SOC changes increased (P < 0.05) with increasing straw-C input and experiment duration. However, the C efficiency decreased significantly (P < 0.01) with these two explanatory factors. No-tillage and crop rotation were found to enhance the SR-induced SOC increase, in both magnitude and efficiency. Straw return sequestrated larger amount of C in acidic and organic-rich soils than in alkaline and organic-poor soils. A machine learning random forest (RF) algorithm showed that the amount of straw-C input was the most important single factor governing the magnitude and efficiency of straw return. However, local agricultural managements and environmental conditions were together the dominant explanatory factors determining the spatial differences in SR-induced SOC stock changes. This entails that by optimizing agricultural managements in regions with favorable environmental conditions the farmer can accumulate more C with minor negative impacts. By clarifying the significance and relative importance of multiple local factors, our findings may aid the development of tailored region-specific straw return policies integrating the SOC increment and its environmental side costs.

Responses of soil organic carbon stock to animal manure application: A new global synthesis integrating the impacts of agricultural managements and environmental conditions.

Enhancing soil organic carbon (SOC) through applying animal manure is of interest for both sustaining cereal production and mitigating greenhouse gas (GHG) emissions. Previous syntheses showed that manuring-induced SOC changes varied substantially with agricultural managements and environmental conditions, while their significance and relative importance to such variability are still largely uncertain. Here, we presented a new synthesis using an updated and balanced database integrating the manuring-induced SOC stock changes and their plausible explanatory factors in 250 observations at global 120 sites. Manure application increased SOC stock by 7.41 ± 1.14 (95% confidence interval, CI) and 8.96 ± 1.83 (95% CI) Mg C ha-1 , respectively, compared to their mineral fertilized (REF-min) and unfertilized (REF-zero) references. Of which approx. 72% and 34% were directly contributed by manure-C input, respectively. Following the IPCC (Intergovernmental Panel on Climate Change) approach, these changes corresponded to the manuring-induced SOC change factors of 1.27 ± 0.04 (95% CI) and 1.40 ± 0.08 (95% CI), respectively. Basing on a balanced database, we identified the amount of manure-C input as the most important factor to the global variations in the resultant SOC stock changes. More importantly, our integrative analysis distinguished the significance of soil properties (e.g., soil pH and initial SOC content) in regulating the efficiency of manure application in enhancing SOC stock. These results indicate that, at the similar rate, applying manure could sequestrate much more carbon in alkaline soils than in neutral and acidic soils. By integrating the impacts of agricultural managements and environmental conditions, our findings would help to develop region-specific tailor-made manure application measures in agriculture and to refine the SOC change factors for regional GHG inventories.