Overestimation of nitrogen（N） uptake requirement is one of the driving forces of the overuse of N fertilization and the low efficiency of N use in China. In this study, we collected data from 1 844 site-years of ric...Overestimation of nitrogen（N） uptake requirement is one of the driving forces of the overuse of N fertilization and the low efficiency of N use in China. In this study, we collected data from 1 844 site-years of rice（Oryza sativa L.） under various rotation cropping systems across the Yangtze River Valley. Selected treatments included without（N0 treatment） and with N application（N treatment） which were recommended by local technicians, with a wide grain range of 1.5–11.9 t ha–1. Across the 1 844 site-years, over 96% of the sites showed yield increase（relative yield〉105%） with N fertilization, and the increase rates decreased from 78.9 to 16.2% within the lowest range 〈4.0 to the highest 〉6.5 t ha–1. To produce one ton of grain, the rice absorbed approximately 17.8 kg N in the N0 treatment and 20.4 kg N in the N treatment. The value of partial factor productivity by N（PFP N） reached a range of 35.2–51.4 kg grain kg–1 with N application under the current recommended N rate. Averaged recovery rate of N（RE N） was above 36.0% in yields below 6.0 t ha–1 and lower than 31.7% in those above 6.0 t ha–1. Soil properties only affected yield increments within low rice yield levels（〈5.5 t ha–1）. There is a poor relationship between N application rates and indigenous nitrogen supply（INS）. From these observations and considering the local INS, we concluded there was a great potential for improvement in regional grain yield and N efficiency.展开更多
目的评价典型重金属污染地区学龄前儿童镉(Cadmium,Cd)暴露健康风险。方法采集某典型重金属污染地区土壤样本和蔬菜可食用部位并检测其Cd浓度,查阅当地空气、小麦、水稻和水的Cd浓度,通过美国国家环境保护局推荐的健康风险评价模型评价...目的评价典型重金属污染地区学龄前儿童镉(Cadmium,Cd)暴露健康风险。方法采集某典型重金属污染地区土壤样本和蔬菜可食用部位并检测其Cd浓度,查阅当地空气、小麦、水稻和水的Cd浓度,通过美国国家环境保护局推荐的健康风险评价模型评价当地学龄前儿童的Cd暴露健康风险,分别采用危险系数(hazard quotient,HQ)和终生增量致癌风险(incremental lifetime cancer risk,ILCR)评估非致癌风险和致癌风险。结果该地区学龄前儿童总的非致癌风险HQ_(总)为4.14,HQ_(经口)为4.10,HQ_(小麦)为2.77,其他途径和介质HQ均<1.00。该地区学龄前儿童总的致癌风险ILCR_(总)为1.54×10^(-3)。各途径中ILCR_(经口)为1.53×10^(-3),各媒介中ILCR_(小麦)>ILCR_(蔬菜)>ILCR_(水稻)>1.00×10^(-4)。结论该典型重金属污染地区学龄前儿童存在Cd暴露的非致癌风险和致癌风险。经口是Cd暴露的主要途径,小麦是非致癌风险的主要贡献者,小麦、蔬菜和水稻是致癌风险的主要贡献者。展开更多
基金the Special Fund for Agro-Scientific Research in the Public Interest in China (201103039)the Fundamental Research Funds for the Central Universities Key Projects, China (2013PY113)+1 种基金the Natural Science Foundation of Hubei Province, China (2013CFB203)the Research Funds of Huazhong Agricultural University, China (52209814032) for providing financial support
文摘Overestimation of nitrogen（N） uptake requirement is one of the driving forces of the overuse of N fertilization and the low efficiency of N use in China. In this study, we collected data from 1 844 site-years of rice（Oryza sativa L.） under various rotation cropping systems across the Yangtze River Valley. Selected treatments included without（N0 treatment） and with N application（N treatment） which were recommended by local technicians, with a wide grain range of 1.5–11.9 t ha–1. Across the 1 844 site-years, over 96% of the sites showed yield increase（relative yield〉105%） with N fertilization, and the increase rates decreased from 78.9 to 16.2% within the lowest range 〈4.0 to the highest 〉6.5 t ha–1. To produce one ton of grain, the rice absorbed approximately 17.8 kg N in the N0 treatment and 20.4 kg N in the N treatment. The value of partial factor productivity by N（PFP N） reached a range of 35.2–51.4 kg grain kg–1 with N application under the current recommended N rate. Averaged recovery rate of N（RE N） was above 36.0% in yields below 6.0 t ha–1 and lower than 31.7% in those above 6.0 t ha–1. Soil properties only affected yield increments within low rice yield levels（〈5.5 t ha–1）. There is a poor relationship between N application rates and indigenous nitrogen supply（INS）. From these observations and considering the local INS, we concluded there was a great potential for improvement in regional grain yield and N efficiency.
文摘目的评价典型重金属污染地区学龄前儿童镉(Cadmium,Cd)暴露健康风险。方法采集某典型重金属污染地区土壤样本和蔬菜可食用部位并检测其Cd浓度,查阅当地空气、小麦、水稻和水的Cd浓度,通过美国国家环境保护局推荐的健康风险评价模型评价当地学龄前儿童的Cd暴露健康风险,分别采用危险系数(hazard quotient,HQ)和终生增量致癌风险(incremental lifetime cancer risk,ILCR)评估非致癌风险和致癌风险。结果该地区学龄前儿童总的非致癌风险HQ_(总)为4.14,HQ_(经口)为4.10,HQ_(小麦)为2.77,其他途径和介质HQ均<1.00。该地区学龄前儿童总的致癌风险ILCR_(总)为1.54×10^(-3)。各途径中ILCR_(经口)为1.53×10^(-3),各媒介中ILCR_(小麦)>ILCR_(蔬菜)>ILCR_(水稻)>1.00×10^(-4)。结论该典型重金属污染地区学龄前儿童存在Cd暴露的非致癌风险和致癌风险。经口是Cd暴露的主要途径,小麦是非致癌风险的主要贡献者,小麦、蔬菜和水稻是致癌风险的主要贡献者。
