Associations between eating alone, its transition and depressive symptoms among Chinese middle-aged and older adults: evidence from two national cohorts.

BACKGROUND: Few studies have explored the longitudinal association between eating alone and depressive symptoms, and have focused on the effect of eating alone transition. This study aims to explore the longitudinal association between eating alone, its transition and depressive symptoms among two national surveys using a cohort study design. METHODS: The participants aged ≥ 45 years were recruited for the 2016 to 2018 waves China Family Panel Data (CFPS) and 2015 to 2018 waves China Health and Retirement Longitudinal Study (CHARLS). Eating alone was assessed by self-reported. Depressive symptoms were evaluated by Center for Epidemiologic Studies Depression Scale. Cox hazard regression was used to explore the associations between eating alone, its transition and depressive symptoms after adjusting for covariates. RESULTS: A total of 21,476 participants were included in this study. The Cox model showed that compared with commensality, eating alone was associated with a higher risk of depressive symptoms, both in the CFPS, CHARLS and pooled analysis. In addition, compared with commensality consistently, the transition from commensality to alone and eating alone consistently were associated with a higher risk of depressive symptoms. The sensitivity analyses showed that the association remained robust. CONCLUSIONS: Eating alone and a change from commensality to eating alone were associated with higher risks of depressive symptoms among Chinese middle-aged and older adults in two cohorts. This study suggested that providing eating partners may be an effective intervention method to prevent depressive symptoms in middle-aged and older adults.

The effect of biochar types on carbon cycles in farmland soils: A meta analysis.

Application of biochar has been demonstrated to be a successful strategy for boosting soil carbon sequestration and altering the agricultural soil carbon cycle. However, in the studies involving biochar worldwide, the effects of different types of biochar on the soil carbon component response direction and increase are not consistent. Therefore, to assess the effects of applying four types of biochar during the soil carbon cycle on carbon components on a farmland, we performed a meta-analysis of 1150 comparisons from 86 peer-reviewed publications. Generally speaking, the types of biochar raw materials have a significant impact on soil carbon cycle. The application of chaff biochar significantly inhibited (10.0 %) soil respiration, while the application of manure biochar (47.0 %), straw biochar (11.2 %) and wood biochar (8.7 %) showed a strong promotion effect on CO2 emission. In addition, although the soil organic C, microbial biomass C and dissolved organic C all had positive responses to the application of the four biochar types, the degree and increase in their response varied greatly due to the differences in biomass raw materials. Moreover, by increasing the biochar rates applied to coarse-textured soils with low average annual rainfall and an average temperature under controlled circumstances, the relative increase in SOC was encouraged. Meanwhile, applying low temperature pyrolytic biochar (≤400 °C) at a lower rate (<25 t/ha) in the long-term experiment (>3 years) is more beneficial to soil C sequestration and emission reduction. Hence, climatic conditions, agricultural management practices, and initial soil properties jointly constrained and influenced the ability of biochar to alter the soil C cycle. Based on this, our research offers a fresh viewpoint for making a profound study biochar-enhanced soil C cycle.

Organic fertilizer substitutions maintain maize yield and mitigate ammonia emissions but increase nitrous oxide emissions.

Organic fertilizer can improve soil structure and enhance the nutrient content in soil and is beneficial to sustainable agricultural development. However, the influence of organic fertilizer substitutions on NH3 and N2O emissions from farmland is unclear. Thus, we set up an organic substitution field experiment in Northeast China. The experiment included six treatments: single application of chemical fertilizers (NPK: 250 kg N ha-1); NO10, 10% reduction in chemical nitrogen fertilizers (225 kg N ha-1) + chicken manure (25 kg N ha-1); NO20, 20% reduction in chemical nitrogen fertilizers (200 kg N ha-1) + chicken manure (50 kg N ha-1); NO30, 30% reduction in chemical nitrogen fertilizers (175 kg N ha-1) + chicken manure (75 kg N ha-1); NO40, 40% reduction in chemical nitrogen fertilizers (150 kg N ha-1) + chicken manure (100 kg N ha-1); and no-nitrogen fertilizer (CK). This experiment investigated the effects of partial substitution of chemical nitrogen fertilizer with organic fertilizer on NH3 and N2O emissions and nitrogen use efficiency in a maize field. The results showed that, compared with chemical N, organic fertilizer mitigated NH3 volatilization but promoted the soil N2O total emissions during the whole growth stage. NH3 cumulative volatilization decreased with the increase in the substitution rate of organic fertilizer. Compared with the NPK treatment, the cumulative volatilization of NH3 in the NO30 and NO40 treatments decreased by 15.24 and 17.92%, respectively. The NO40 treatment had the highest N2O emission in the whole growth stage, and the N2O emission of the NO40 treatment increased by 10.72% compared to the NPK treatment. Moreover, the yield, partial factor productivity (PFP), nitrogen harvest index (NHI), and apparent nitrogen recovery efficiency (NRE) of NO30 treatment were the highest of all treatments, and the yields, PFP, plant N accumulation, grain N accumulation, and the cumulative emissions of NH3 and N2O were similar to N20 treatment. In conclusion, nitrogen fertilizer use efficiency was enhanced, decreasing environmental pollution from livestock under organic fertilizer substitution conditions. We suggested 20% or 30% substitution rates of organic fertilizer were proper.

Response of Wheat, Maize, and Rice to Changes in Temperature, Precipitation, CO2 Concentration, and Uncertainty Based on Crop Simulation Approaches.

The influence of global climate change on agricultural productivity is an essential issue of ongoing concern. The growth and development of wheat, maize, and rice are influenced by elevated atmospheric CO2 concentrations, increased temperatures, and seasonal rainfall patterns. However, due to differences in research methodologies (e.g., crop models, climate models, and climate scenarios), there is uncertainty in the existing studies regarding the magnitude and direction of future climate change impacts on crop yields. In order to completely assess the possible consequences of climate change and adaptation measures on crop production and to analyze the associated uncertainties, a database of future crop yield changes was developed using 68 published studies (including 1842 samples). A local polynomial approach was used with the full dataset to investigate the response of crop yield changes to variations in maximum and minimum temperatures, mean temperature, precipitation, and CO2 concentrations. Then, a linear mixed-effects regression model was utilized with the limited dataset to explore the quantitative relationships between them. It was found that maximum temperature, precipitation, adaptation measure, study area, and climate model had significant effects on changes in crop yield. Crop yield will decline by 4.21% for each 1 °C rise in maximum temperature and increase by 0.43% for each 1% rise in precipitation. While higher CO2 concentrations and suitable management strategies could mitigate the negative effects of warming temperatures, crop yield with adaptation measures increased by 64.09% compared to crop yield without adaptation measures. Moreover, the uncertainty of simulations can be decreased by using numerous climate models. The results may be utilized to guide policy regarding the influence of climate change and to promote the creation of adaptation plans that will increase crop systems' resilience in the future.

Agricultural diversification promotes sustainable and resilient global rice production.

Rice is a staple food for half of the human population, but the effects of diversification on yields, economy, biodiversity and ecosystem services have not been synthesized. Here we quantify diversification effects on environmental and socio-economic aspects of global rice production. We performed a second-order meta-analysis based on 25 first-order meta-analyses covering four decades of research, showing that diversification can maintain soil fertility, nutrient cycling, carbon sequestration and yield. We used three individual first-order meta-analyses based on 39 articles to close major research gaps on the effects of diversification on economy, biodiversity and pest control, showing that agricultural diversification can increase biodiversity by 40%, improve economy by 26% and reduce crop damage by 31%. Trade-off analysis showed that agricultural diversification in rice production promotes win-win scenarios between yield and other ecosystem services in 81% of all cases. Knowledge gaps remain in understanding the spatial and temporal effects of specific diversification practices and trade-offs.

Effects of Different Types of Water and Nitrogen Fertilizer Management on Greenhouse Gas Emissions, Yield, and Water Consumption of Paddy Fields in Cold Region of China.

Water management and nitrogen (N) fertilizers are the two main driving factors of greenhouse gas emissions. In this paper, two irrigation modes, controlled irrigation (CI) and flood irrigation (FI), and four nitrogen fertilizer levels (N0: 0, N1:,85, N2:,110, and N3:,135 kg·hm-2) were set to study the effect of different irrigation modes and N fertilizer amount on greenhouse-gas emissions of paddy fields in cold region by using the static chamber-gas chromatograph method; yield and water consumption were also analyzed. The results showed that, compared with FI, CI significantly reduced CH4 emissions by 19.42~46.94%, but increased N2O emissions by 5.66~11.85%. Under the two irrigation modes, N fertilizers could significantly increase N2O emissions, but the CH4 emissions of each N treatment showed few differences. Compared with FI, appropriate N application under CI could significantly increase grain number per spike, seed-setting rate, and 1000-grain weight, thus increasing yield. Under the two irrigation modes, water consumption increased with the increase of N application rate, and the total water consumption of CI was significantly lower than that of FI. The global warming potential (GWP) of CI was significantly smaller than that of FI. The trend of GWP in each treatment was similar to that of CH4. Through comprehensive comparison and analysis of water productivity (WP), gas emission intensity (GHGI), and the yield of each treatment, we found that CI+N2 treatment had the highest WP (2.05 kg·m-3) and lowest GHGI (0.37 kg CO2-eq·kg-1), while maintaining high yield (10224.4 kg·hm-2). The results of this study provide an important basis for guiding high yield, water-savings, and emission reduction of paddy fields in cold regions.

Characterizing Spatiotemporal Dynamics of CH4 Fluxes from Rice Paddies of Cold Region in Heilongjiang Province under Climate Change.

Paddy fields have become a major global anthropogenic CH4 emission source, and climate change affects CH4 emissions from paddy ecosystems by changing crop growth and the soil environment. It has been recognized that Heilongjiang Province has become an important source of CH4 emission due to its dramatically increased rice planting area, while less attention has been paid to characterize the effects of climate change on the spatiotemporal dynamics of CH4 fluxes. In this study, we used the calibrated and validated Long Ashton Research Station Weather Generator (LARS-WG) model and DeNitrification-DeComposition (DNDC) model to simulate historical and future CH4 fluxes under RCP 4.5 and RCP 8.5 of four global climate models (GCMs) in Heilongjiang Province. During 1960⁻2015, the average CH4 fluxes and climatic tendencies were 145.56 kg C/ha and 11.88 kg C/ha/(10a), respectively. Spatially, the CH4 fluxes showed a decreasing trend from west to east, and the climatic tendencies in the northern and western parts were higher. During 2021⁻2080, the annual average CH4 fluxes under RCP 4.5 and RCP 8.5 were predicted to be 213.46 kg C/ha and 252.19 kg C/ha, respectively, and their spatial distributions were similar to the historical distribution. The average climatic tendencies were 13.40 kg C/ha/(10a) and 29.86 kg C/ha/(10a), respectively, which decreased from west to east. The simulation scenario analysis showed that atmospheric CO2 concentration and temperature affected CH4 fluxes by changing soil organic carbon (SOC) content and plant biomass. This study indicated that a paddy ecosystem in a cold region is an important part of China's greenhouse gas emission inventory in future scenarios.