[Objective] The aim was to explore effects of application postponing of N fertilizer and the mechanism of yield increase in order to provide references for N fertilizer application in a rational way. [Method] In a sup...[Objective] The aim was to explore effects of application postponing of N fertilizer and the mechanism of yield increase in order to provide references for N fertilizer application in a rational way. [Method] In a super-high yielded region of summer maize, field experiment was conducted to research effects of N fertilizer postponing on key enzymes of N metabolism, yield of maize and N fertilizer use. [Result] After application of N fertilizer was postponed, NR, SPS and GS activities of ear-leaf of summer maize increased by 11.99%-34.87%, 8.25%-10.64% and 10.00%- 16.81% on the 28^th d of silking; content of soluble sugar in leaves enhanced signifi- cantly and accumulated nitrogen increased by 5.00%-9.74% in mature stage. The postponing fertilization of ＂30% of fertilizer in seedling stage＋30% of fertilizer in flare- opening stage＋40% of fertilizer in silking stage meets N demands of summer maize in late growth period. Compared with conventional fertilization, the maize yield, agro- nomic efficiency and use of N fertilizer all improved by 5.05%, 1.75 kg/kg and 6.87%, respectively, after application postponed. [Conclusion] Application postponing of N fertilizer maintains activity of NR, GS and SPS higher and coordinates metabolism of C and N in late growth period, to further improve yield of maize.展开更多
Nitrogen(N)fertilization increases rice yield,but inappropriate N fertilizer application increases N loss and the risk of environmental pollution.Short-term fertilizer postponing(FP)generally reduces N apparent surplu...Nitrogen(N)fertilization increases rice yield,but inappropriate N fertilizer application increases N loss and the risk of environmental pollution.Short-term fertilizer postponing(FP)generally reduces N apparent surplus and increases rice yields,but the effects of long-term FP on N surplus and rice yields remain unknown.Our study was the first to investigate the impacts of long-term FP(11 years)on N apparent surplus and rice yields.FP effects in the short term(≤6 years)did not affect rice yields,whereas FP effects in the long term(>6 years)increased rice yields by 13.9%compared with conventional fertilization(CF).FP did not affect panicles per unit area,1000-kernel weight,and filled-kernel rate,but spikelets per panicle increased over time due to spikelet formation stimulation.FP also reduced the N apparent surplus over time more strongly than CF owing to higher N accumulation and N utilization efficiency.FP effects in the long term also significantly increased soil organic matter,total N,and NH4_(+)^(-)N content.Our results were supported by a pot experiment,showing that rice yields in soils with a history of FP were significantly higher than those for soils without a history of FP,indicating that FP increased rice yields more strongly in later years mainly because of soil quality improvement.Our findings suggest that longterm FP can reduce N loss while increasing rice yields by improving soil quality.展开更多
Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.Aft...Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.After using the decomposition technique to isolate the effects of parity composition and childbearing schedule in each of the three countries,the article presents a quantitative examination of the factors that underlie dynamic changes and cross-national differences of MACs.Results indicate that the MAC of China experienced a decrease between 1990 and 1995,followed by sustained growth afterwards.The increase of MAC in China has been driven by the postponement of childbearing and changes in parity composition,with the former playing a larger role.The mechanisms underlying the patterns since 2010 deserve special attention.Compared with Japan and South Korea,China has had relatively lower MAC during the last 25 years;the three countries demonstrate different patterns in terms of the roles of parity composition and birth timing.The accuracy of MAC in identifying the timing of period fertility and the policy implications of timing on upturning fertility level are discussed.展开更多
基金Crop Harvest Technology and Engineering in the Twelfth Five-year Plan (2011BAD16B15-2)Special Foundation of National Modern Maize Industrial Technology System(nycytx-02-17)Cooperation Project of China-International Plant Nutrition Research Institute (NMBF-HenanAU-2009)~~
文摘[Objective] The aim was to explore effects of application postponing of N fertilizer and the mechanism of yield increase in order to provide references for N fertilizer application in a rational way. [Method] In a super-high yielded region of summer maize, field experiment was conducted to research effects of N fertilizer postponing on key enzymes of N metabolism, yield of maize and N fertilizer use. [Result] After application of N fertilizer was postponed, NR, SPS and GS activities of ear-leaf of summer maize increased by 11.99%-34.87%, 8.25%-10.64% and 10.00%- 16.81% on the 28^th d of silking; content of soluble sugar in leaves enhanced signifi- cantly and accumulated nitrogen increased by 5.00%-9.74% in mature stage. The postponing fertilization of ＂30% of fertilizer in seedling stage＋30% of fertilizer in flare- opening stage＋40% of fertilizer in silking stage meets N demands of summer maize in late growth period. Compared with conventional fertilization, the maize yield, agro- nomic efficiency and use of N fertilizer all improved by 5.05%, 1.75 kg/kg and 6.87%, respectively, after application postponed. [Conclusion] Application postponing of N fertilizer maintains activity of NR, GS and SPS higher and coordinates metabolism of C and N in late growth period, to further improve yield of maize.
基金Funding was provided by the National Key Research and Development Program of China(2017YFD0301203,2017YFD0300100,and 2018YFD0300803)Jiangsu Agriculture Science and Technology Innovation Fund(CX(18)1002).
文摘Nitrogen(N)fertilization increases rice yield,but inappropriate N fertilizer application increases N loss and the risk of environmental pollution.Short-term fertilizer postponing(FP)generally reduces N apparent surplus and increases rice yields,but the effects of long-term FP on N surplus and rice yields remain unknown.Our study was the first to investigate the impacts of long-term FP(11 years)on N apparent surplus and rice yields.FP effects in the short term(≤6 years)did not affect rice yields,whereas FP effects in the long term(>6 years)increased rice yields by 13.9%compared with conventional fertilization(CF).FP did not affect panicles per unit area,1000-kernel weight,and filled-kernel rate,but spikelets per panicle increased over time due to spikelet formation stimulation.FP also reduced the N apparent surplus over time more strongly than CF owing to higher N accumulation and N utilization efficiency.FP effects in the long term also significantly increased soil organic matter,total N,and NH4_(+)^(-)N content.Our results were supported by a pot experiment,showing that rice yields in soils with a history of FP were significantly higher than those for soils without a history of FP,indicating that FP increased rice yields more strongly in later years mainly because of soil quality improvement.Our findings suggest that longterm FP can reduce N loss while increasing rice yields by improving soil quality.
基金supported by the Project Study on Family Transition in China(16JJD840013)of the Key Research Centers of Minister of Education.
文摘Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.After using the decomposition technique to isolate the effects of parity composition and childbearing schedule in each of the three countries,the article presents a quantitative examination of the factors that underlie dynamic changes and cross-national differences of MACs.Results indicate that the MAC of China experienced a decrease between 1990 and 1995,followed by sustained growth afterwards.The increase of MAC in China has been driven by the postponement of childbearing and changes in parity composition,with the former playing a larger role.The mechanisms underlying the patterns since 2010 deserve special attention.Compared with Japan and South Korea,China has had relatively lower MAC during the last 25 years;the three countries demonstrate different patterns in terms of the roles of parity composition and birth timing.The accuracy of MAC in identifying the timing of period fertility and the policy implications of timing on upturning fertility level are discussed.
