【目的】明确京津冀地区农牧系统氮素流动及平衡特征,解析化学氮肥减施潜力,从而为该地区化肥零增长和农业绿色发展提供依据。【方法】通过收集文献数据及2017年统计数据,采用Nufer(nutrient flows in food chain,environment and resou...【目的】明确京津冀地区农牧系统氮素流动及平衡特征,解析化学氮肥减施潜力,从而为该地区化肥零增长和农业绿色发展提供依据。【方法】通过收集文献数据及2017年统计数据,采用Nufer(nutrient flows in food chain,environment and resources use)模型,以“农田–畜牧”系统为研究对象,量化京津冀地区农牧系统氮素流动特征及利用效率,并针对输入输出平衡施氮和增加畜禽粪便还田量替代化肥两种措施,通过情景分析评估该地区化学氮肥减施潜力。【结果】京津冀地区农田系统和畜牧系统氮素输入量分别为296.1万t和133.6万t,农牧系统氮素总体输入量为306.6万t,其中化学氮肥是最大的输入项,占总输入量的62.5%。农田系统、畜牧系统氮素利用率分别为40.6%和25.0%,农牧系统整体氮素利用率为33.8%,农牧系统氮素循环再利用率为55.2%,生产单位氮含量食物产品所需氮素投入量为3.0 kg/kg。在该地区,土壤氮素累积量为51.2万t(占总输入量的16.7%),环境排放总量为140.4万t(占总输入量的45.8%)。环境排放中,氨挥发(包括农田和畜禽粪便氨挥发)和畜禽粪便水体排放与堆置为占比最大的两种损失途径,分别占总氮投入量的21.0%和9.5%。氮素土壤累积和畜禽粪便水体排放与堆置为两种最易调控的损失途径。通过输入输出平衡降低氮素土壤累积量,此地区有40%的氮肥减施潜力,此时,农牧系统氮素总投入量为230.0万t,农田和农牧系统氮素利用率分别较当前增加14.1和11.3个百分点;继续优化氮素管理,增加部分畜禽粪便还田量(减少水体排放与堆置部分)以替代化肥,则该地区有50%的氮肥减施潜力,且在此状态下,农牧系统氮素总投入量为210.8万t,较当前降低31.2%,农田系统和农牧系统氮素利用率分别增加15.3和15.4个百分点,氮素环境排放量降低36.2%,氮素循环再利用率增加20.0%,食物氮代价降低33.3%。【结论】化学氮肥施用量大,农牧分离是京津冀地区农牧系统氮素利用效率低的主要原因。在农牧系统氮素管理中,通过平衡作物生产中的氮素投入,系统氮素投入的减少潜力为40%。如果能进一步合理利用有机资源,增加畜禽粪便还田率,化学氮肥减施的总潜力可达50%,并可提高氮素利用效率,有效降低氮素的环境排放总量。展开更多
Quantification of currently attainable yield and fertilizer requirements can provide detailed information for assessing the food supply capacity and offer data support for agricultural decision-making.Datasets from a ...Quantification of currently attainable yield and fertilizer requirements can provide detailed information for assessing the food supply capacity and offer data support for agricultural decision-making.Datasets from a total of 5408 field experiments were collected from 2000 to 2015 across the major wheat production regions in China to analyze the spatial distribution of wheat yield,the soil nutrient supply capacity(represented by relative yield,defined as the ratio of the yield under the omission of one of nitrogen(N),phosphorus(P)and potassium(K)to the yield under the full NPK fertilizer application),and N,P and K fertilizer requirements by combining the kriging interpolation method with the Nutrient Expert Decision Support System for Wheat.The results indicated that the average attainable yield was 6.4 t ha^(−1),with a coefficient of variation(CV)of 24.9% across all sites.The yields in North-central China(NCC)and the northern part of the Middle and Lower reaches of the Yangtze River(MLYR)were generally higher than 7 t ha^(−1),whereas the yields in Southwest China(SWC),Northeast China(NEC),and the eastern part of Northwest China(NWC)were usually less than 6 t ha^(−1).The precentage of area having a relative yield above 0.70,0.85,and 0.85 for N,P,and K fertilizers accounted for 52.3,74.7,and 95.9%,respectively.Variation existed in N,P,and K fertilizer requirements,with a CV of 24.8,23.9,and 29.9%,respectively,across all sites.More fertilizer was needed in NCC and the northern part of the MLYR than in other regions.The average fertilizer requirement was 162,72,and 57 kg ha^(−1) for N,P2O5,and K2O fertilizers,respectively,across all sites.The incorporation of the spatial variation of attainable yield and fertilizer requirements into wheat production practices would benefit sustainable wheat production and environmental safety.展开更多
【目的】探讨肺保护通气策略对ARDS患者的疗效及对右心功能的影响。【方法】选取2016年1月至2017年6月在我院重症医学科住院的ARDS患者共52例,年龄(48±7)岁。将所有患者随机分为对照组(24例)和肺保护组(28例),其中对照组采用潮气量...【目的】探讨肺保护通气策略对ARDS患者的疗效及对右心功能的影响。【方法】选取2016年1月至2017年6月在我院重症医学科住院的ARDS患者共52例,年龄(48±7)岁。将所有患者随机分为对照组(24例)和肺保护组(28例),其中对照组采用潮气量8~15 m L/kg标准体质量,PEEP 4~8 cm H2O,平台压30~35 cm H2O;肺保护组采用潮气量6 m L/kg标准体质量,PEEP采用ARDSNET滴定法(PEEP-Fi O2表)进行设置,平台压<30cm H2O。收集患者不同通气时段Pa O2、PCO2、OI、乳酸、TAPSE、RVarea/LVarea、E/A、E/e、PASP、IVC等指标并进行统计分析。【结果】通气24 h肺保护组TAPSE、E/e高于对照组,PASP低于对照组(P<0.05);通气48 h肺保护组OI、Pa O2、PCO2、乳酸均高于对照组(P<0.05),肺保护组TAPSE高于对照组,PASP和IVC低于对照组(P<0.05)。肺保护组机械通气时间、总住院时间短于对照组(P<0.01)。【结论】肺保护通气策略在改善ARDS患者氧合方面明显比常规通气策略更有优势,且对右心功能的影响小。展开更多
Understanding the spatial-temporal dynamics of crop nitrogen(N)use efficiency(NUE)and the relationship with explanatory environmental variables can support land-use management and policymaking.Nevertheless,the applica...Understanding the spatial-temporal dynamics of crop nitrogen(N)use efficiency(NUE)and the relationship with explanatory environmental variables can support land-use management and policymaking.Nevertheless,the application of statistical models for evaluating the explanatory variables of space-time variation in crop NUE is still under-researched.In this study,stepwise multiple linear regression(SMLR)and Random Forest(RF)were used to evaluate the spatial and temporal variation of NUE indicators(i.e.,partial factor productivity of N(PFPN);partial nutrient balance of N(PNBN))at county scale in Northeast China(Heilongjiang,Liaoning and Jilin provinces)from 1990 to 2015.Explanatory variables included agricultural management practices,topography,climate,economy,soil and crop types.Results revealed that the PFPN was higher in the northern parts and lower in the center of the Northeast China and PNBN increased from southern to northern parts during the 1990–2015 period.The NUE indicators decreased with time in most counties during the study period.The model efficiency coefficients of the SMLR and RF models were 0.44 and 0.84 for PFPN,and 0.67 and 0.89 for PNBN,respectively.The RF model had higher relative importance of soil and climatic covariates and lower relative importance of crop covariates compared to the SMLR model.The planting area index of vegetables and beans,soil clay content,saturated water content,enhanced vegetation index in November&December,soil bulk density,and annual minimum temperature were the main explanatory variables for both NUE indicators.This is the first study to show the quantitative relative importance of explanatory variables for NUE at a county level in Northeast China using RF and SMLR.This novel study gives reference measurements to improve crop NUE which is one of the most effective means of managing N for sustainable development,ensuring food security,alleviating environmental degradation and increasing farmer’s profitability.展开更多
文摘【目的】明确京津冀地区农牧系统氮素流动及平衡特征,解析化学氮肥减施潜力,从而为该地区化肥零增长和农业绿色发展提供依据。【方法】通过收集文献数据及2017年统计数据,采用Nufer(nutrient flows in food chain,environment and resources use)模型,以“农田–畜牧”系统为研究对象,量化京津冀地区农牧系统氮素流动特征及利用效率,并针对输入输出平衡施氮和增加畜禽粪便还田量替代化肥两种措施,通过情景分析评估该地区化学氮肥减施潜力。【结果】京津冀地区农田系统和畜牧系统氮素输入量分别为296.1万t和133.6万t,农牧系统氮素总体输入量为306.6万t,其中化学氮肥是最大的输入项,占总输入量的62.5%。农田系统、畜牧系统氮素利用率分别为40.6%和25.0%,农牧系统整体氮素利用率为33.8%,农牧系统氮素循环再利用率为55.2%,生产单位氮含量食物产品所需氮素投入量为3.0 kg/kg。在该地区,土壤氮素累积量为51.2万t(占总输入量的16.7%),环境排放总量为140.4万t(占总输入量的45.8%)。环境排放中,氨挥发(包括农田和畜禽粪便氨挥发)和畜禽粪便水体排放与堆置为占比最大的两种损失途径,分别占总氮投入量的21.0%和9.5%。氮素土壤累积和畜禽粪便水体排放与堆置为两种最易调控的损失途径。通过输入输出平衡降低氮素土壤累积量,此地区有40%的氮肥减施潜力,此时,农牧系统氮素总投入量为230.0万t,农田和农牧系统氮素利用率分别较当前增加14.1和11.3个百分点;继续优化氮素管理,增加部分畜禽粪便还田量(减少水体排放与堆置部分)以替代化肥,则该地区有50%的氮肥减施潜力,且在此状态下,农牧系统氮素总投入量为210.8万t,较当前降低31.2%,农田系统和农牧系统氮素利用率分别增加15.3和15.4个百分点,氮素环境排放量降低36.2%,氮素循环再利用率增加20.0%,食物氮代价降低33.3%。【结论】化学氮肥施用量大,农牧分离是京津冀地区农牧系统氮素利用效率低的主要原因。在农牧系统氮素管理中,通过平衡作物生产中的氮素投入,系统氮素投入的减少潜力为40%。如果能进一步合理利用有机资源,增加畜禽粪便还田率,化学氮肥减施的总潜力可达50%,并可提高氮素利用效率,有效降低氮素的环境排放总量。
基金This research was supported by the National Key R&D Program of China(2016YFD0200101)the National Natural Science Foundation of China(31801938).
文摘Quantification of currently attainable yield and fertilizer requirements can provide detailed information for assessing the food supply capacity and offer data support for agricultural decision-making.Datasets from a total of 5408 field experiments were collected from 2000 to 2015 across the major wheat production regions in China to analyze the spatial distribution of wheat yield,the soil nutrient supply capacity(represented by relative yield,defined as the ratio of the yield under the omission of one of nitrogen(N),phosphorus(P)and potassium(K)to the yield under the full NPK fertilizer application),and N,P and K fertilizer requirements by combining the kriging interpolation method with the Nutrient Expert Decision Support System for Wheat.The results indicated that the average attainable yield was 6.4 t ha^(−1),with a coefficient of variation(CV)of 24.9% across all sites.The yields in North-central China(NCC)and the northern part of the Middle and Lower reaches of the Yangtze River(MLYR)were generally higher than 7 t ha^(−1),whereas the yields in Southwest China(SWC),Northeast China(NEC),and the eastern part of Northwest China(NWC)were usually less than 6 t ha^(−1).The precentage of area having a relative yield above 0.70,0.85,and 0.85 for N,P,and K fertilizers accounted for 52.3,74.7,and 95.9%,respectively.Variation existed in N,P,and K fertilizer requirements,with a CV of 24.8,23.9,and 29.9%,respectively,across all sites.More fertilizer was needed in NCC and the northern part of the MLYR than in other regions.The average fertilizer requirement was 162,72,and 57 kg ha^(−1) for N,P2O5,and K2O fertilizers,respectively,across all sites.The incorporation of the spatial variation of attainable yield and fertilizer requirements into wheat production practices would benefit sustainable wheat production and environmental safety.
文摘【目的】探讨肺保护通气策略对ARDS患者的疗效及对右心功能的影响。【方法】选取2016年1月至2017年6月在我院重症医学科住院的ARDS患者共52例,年龄(48±7)岁。将所有患者随机分为对照组(24例)和肺保护组(28例),其中对照组采用潮气量8~15 m L/kg标准体质量,PEEP 4~8 cm H2O,平台压30~35 cm H2O;肺保护组采用潮气量6 m L/kg标准体质量,PEEP采用ARDSNET滴定法(PEEP-Fi O2表)进行设置,平台压<30cm H2O。收集患者不同通气时段Pa O2、PCO2、OI、乳酸、TAPSE、RVarea/LVarea、E/A、E/e、PASP、IVC等指标并进行统计分析。【结果】通气24 h肺保护组TAPSE、E/e高于对照组,PASP低于对照组(P<0.05);通气48 h肺保护组OI、Pa O2、PCO2、乳酸均高于对照组(P<0.05),肺保护组TAPSE高于对照组,PASP和IVC低于对照组(P<0.05)。肺保护组机械通气时间、总住院时间短于对照组(P<0.01)。【结论】肺保护通气策略在改善ARDS患者氧合方面明显比常规通气策略更有优势,且对右心功能的影响小。
基金the China Scholarship Council(CSC)(201903250115)the National Natural Science Foundation of China(31972515)the China Agriculture Research System of MOF and MARA(CARS-09-P31).
文摘Understanding the spatial-temporal dynamics of crop nitrogen(N)use efficiency(NUE)and the relationship with explanatory environmental variables can support land-use management and policymaking.Nevertheless,the application of statistical models for evaluating the explanatory variables of space-time variation in crop NUE is still under-researched.In this study,stepwise multiple linear regression(SMLR)and Random Forest(RF)were used to evaluate the spatial and temporal variation of NUE indicators(i.e.,partial factor productivity of N(PFPN);partial nutrient balance of N(PNBN))at county scale in Northeast China(Heilongjiang,Liaoning and Jilin provinces)from 1990 to 2015.Explanatory variables included agricultural management practices,topography,climate,economy,soil and crop types.Results revealed that the PFPN was higher in the northern parts and lower in the center of the Northeast China and PNBN increased from southern to northern parts during the 1990–2015 period.The NUE indicators decreased with time in most counties during the study period.The model efficiency coefficients of the SMLR and RF models were 0.44 and 0.84 for PFPN,and 0.67 and 0.89 for PNBN,respectively.The RF model had higher relative importance of soil and climatic covariates and lower relative importance of crop covariates compared to the SMLR model.The planting area index of vegetables and beans,soil clay content,saturated water content,enhanced vegetation index in November&December,soil bulk density,and annual minimum temperature were the main explanatory variables for both NUE indicators.This is the first study to show the quantitative relative importance of explanatory variables for NUE at a county level in Northeast China using RF and SMLR.This novel study gives reference measurements to improve crop NUE which is one of the most effective means of managing N for sustainable development,ensuring food security,alleviating environmental degradation and increasing farmer’s profitability.
