Global nitrogen （N） emission and deposition have been increased rapidly due to massive mobilization of N which may have long- reaching impacts on ecosystems. Many agricultural and forest ecosystems have been identif...Global nitrogen （N） emission and deposition have been increased rapidly due to massive mobilization of N which may have long- reaching impacts on ecosystems. Many agricultural and forest ecosystems have been identified as secondary N sources. In the present study, the input-output budget of inorganic N in a small forested watershed of subtropical China was investigated. Inorganic N wet deposition and discharge by stream water were monitored from March, 2007 to February, 2009. The concentrations and fluxes of inorganic N in wet precipitation and stream water and net retention of N were calculated. Global N input by dry deposition and biological fixation and N output by denitrification for forested watersheds elsewhere were reported as references to evaluate whether the studied forested watershed is a source or a sink for N. The results show that the inorganic N output by the stream water is mainly caused by NO3-N even though the input is dominated by NH4＋-N. The mean flux of inorganic N input by wet precipitation and output by stream water is 1.672 and 0.537 g N/（m2.yr）, respectively, which indicates that most of inorganic N input is retained in the forested watershed. Net retention of inorganic N reaches 1.135 g N/（m2.yr） considering wet precipitation as the main input and stream water as the main output, ff N input by dry deposition and biological fixation and output by denitlification are taken into account, this subtropical forested watershed currently acts as a considerable sink for N, with a net sink ranging from 1.309 to 1.913 g N/（m2-yr） which may enhance carbon sequestration of the terrestrial ecosystem.展开更多
The photosynthetic characteristics of flag leaf and the accumulation and remobilization of pre-anthesis dry mass（DM） and nitrogen（N） in vegetable organs in nine wheat cultivars under different source-sink manipula...The photosynthetic characteristics of flag leaf and the accumulation and remobilization of pre-anthesis dry mass（DM） and nitrogen（N） in vegetable organs in nine wheat cultivars under different source-sink manipulation treatments including defoliation（DF）, spike shading（SS） and half spikelets removal（SR） were investigated. Results showed that the SS treatment increased the photosynthetic rate（Pn） of flag leaf in source limited cultivar, but had no significant effect on sink limited cultivar. The SR treatment decreased the Pn of flag leaf. Grain DM accumulation was limited by source in some cultivars, in other cultivars, it was limited by sink. Grain N accumulation was mainly limited by source supply. The contribution of pre-anthesis dry mass to grain yield from high to low was stem, leaf and chaff, while the contribution of pre-anthesis N to grain N from high to low was leaf, stem and chaff. Cultivars S7221 and TA9818 can increase the contribution of remobilization of DM and N to grain at the maximum ratio under reducing source treatments, which may be the major reason for these cultivars having lower decrease in grain yield and N content under reducing source treatments.展开更多
Non-point-source pollution has become a major threat to the water quality of the Three Gorges Reservoir(TGR);however,nutrient loadings from terrestrial sources are unclear due to a lack of in situ monitoring.A represe...Non-point-source pollution has become a major threat to the water quality of the Three Gorges Reservoir(TGR);however,nutrient loadings from terrestrial sources are unclear due to a lack of in situ monitoring.A representative small watershed in the central part of the TGR area was selected to monitor the loss of nitrogen(N) and phosphorous(P) continuously along with the runoff from 2007 through 2009 to understand the exact sources and loadings.Results show that the non-point-source nitrogen and phosphorus comes mainly from the storm runoff from residential areas,citrus orchards and sloping croplands,which contributes up to 76% of the loadings in this watershed.Thus,a crucial measure for controlling non-point-source pollution is to intercept storm runoff from the three sources.Paddy fields provide a sink for non-point-source N and P by intercepting the runoff and sediment along with their different forms of nitrogen and phosphorus.The N and P removal efficiency by paddy fields from residential areas is within the range of 56% to 98%.Paddy fields are an important land-use option for reducing the non-point-source loading of N and P in the TGR area.展开更多
By removing panicles and spikelets, the effects of nitrogen supply-demand balance(NSDB)on nitrogen translocation and senescence of leaves at different positions of the same stem in rice plant were studied. The results...By removing panicles and spikelets, the effects of nitrogen supply-demand balance(NSDB)on nitrogen translocation and senescence of leaves at different positions of the same stem in rice plant were studied. The results showed that under NSDB<0(CK), nitrogen translocation and senescence of the top 4 leaves was normal. Nitrogen exported from the top leaves(LFT)especially the top 4 leaves decreased remarkably with increase of NSDB. thus, their MDA contents and differences in color(SPAD value)decreased, while the activities of SOD and CAT increased. Under NSDB>0(panicle removal), N accumulation of the top 4 leaves increased significantly, and the leaf senescence process was delayed. The results also indicated that the color of the 4th LFT was mainly affected by NSDB among the top 4 leaves and was lighter than the 3rd LFT when nitrogen supply was insufficient for the sink need.展开更多
To study whether integrative fertilization [growing milk vetch in winter and reducing the dose of chemical nitrogen(N) fertilizer] can improve rice yield, and to reveal the underlying regulatory mechanisms for integra...To study whether integrative fertilization [growing milk vetch in winter and reducing the dose of chemical nitrogen(N) fertilizer] can improve rice yield, and to reveal the underlying regulatory mechanisms for integrative fertilization, a three-year field trial including two treatments, milk vetch-rice-rice(MRR) and winter fallow-rice-rice(FRR), was conducted in 2010, 2011 and 2012.Our results demonstrated that the MRR treatment could significantly improve rice yield compared with the FRR treatment, especially when the application ratio of milk vetch and chemical fertilizer was 1:2.MRR treatment increased the effective panicle number and the spikelet number per panicle.In addition, a higher tillering number, leaf area index, photosynthetic-potential and photosynthetic-potential to grain ratio were observed in MRR treatment, which could provide enough dry matter for yield formation.Moreover, in MRR treatment, we discovered a higher transportation ratio and transformation ratio of dry matter in culm and leaves, and a stronger total sink capacity and spikelet-root bleeding intensity at the heading stage and 15 d after heading.Furthermore, the MRR treatment showed higher total N, phosphorus and potassium uptakes than FRR treatment, which was associated with the higher root dry weight in each soil layers.These results suggest that growing milk vetch in winter can improve rice yield under less chemical N fertilizer application, which is due to the improvement of soil nutrient status and the increased of rice root growth and development.展开更多
Grain filling, a crucial stage of grain yield formation in rice, is usually affected by the panicle nitrogen （N） fertilization. Field and pot culture experiments were conducted to explore the underlying mechanisms o...Grain filling, a crucial stage of grain yield formation in rice, is usually affected by the panicle nitrogen （N） fertilization. Field and pot culture experiments were conducted to explore the underlying mechanisms of N effect. Two rice cultivars with high lodging resistance were grown in the field and pot. Four panicle N fertilization treatments were conducted in 2006 and repeated in 2007. The result showed that medium level of panicle N fertilization treatment （NM） enhanced the accumulation and translocation of non-structural carbohydrate （NSC） in the stem and sheath. Compared with non-nitrogen treatment （NO）, NM promoted the translocation of labeled ^13C from stem and sheath to grain. But, low level of panicle N fertilization treatment （NL） and high level of panicle N fertilization treatment （NH） showed the negative effect. The endosperm cell, grain length, and grain width of NM increased more quickly than that of NO from 4 to 10 d after anthesis. During the early period of grain filling, sucrose-phosphate synthase （EC 2.4.1.14, SPS） activity were significantly higher for the NM treatment than those of the NL and NH treatments. Sucrose synthase （EC 2.4.1.13, SuSase） activity in the grains was substantially enhanced by NM, with the duration of higher activity being longer than those of the other treatments. At maturing stage, NM significantly increased the filled grain number, the seed-setting rate, and the grain weight compared with NL and NH. The results suggest that NM have a positive effect on the activities of enzymes of physiological importance, thereby increasing the grain size and promoting grain filling.展开更多
基金supported by the National Natural Science Foundation of China (No. 41071141,40625001)the International Foundation of Science (No. C/4077-2)the fund from Institute of Soil Science,Chinese Academy of Sciences (No. ISSASIP0704)
文摘Global nitrogen （N） emission and deposition have been increased rapidly due to massive mobilization of N which may have long- reaching impacts on ecosystems. Many agricultural and forest ecosystems have been identified as secondary N sources. In the present study, the input-output budget of inorganic N in a small forested watershed of subtropical China was investigated. Inorganic N wet deposition and discharge by stream water were monitored from March, 2007 to February, 2009. The concentrations and fluxes of inorganic N in wet precipitation and stream water and net retention of N were calculated. Global N input by dry deposition and biological fixation and N output by denitrification for forested watersheds elsewhere were reported as references to evaluate whether the studied forested watershed is a source or a sink for N. The results show that the inorganic N output by the stream water is mainly caused by NO3-N even though the input is dominated by NH4＋-N. The mean flux of inorganic N input by wet precipitation and output by stream water is 1.672 and 0.537 g N/（m2.yr）, respectively, which indicates that most of inorganic N input is retained in the forested watershed. Net retention of inorganic N reaches 1.135 g N/（m2.yr） considering wet precipitation as the main input and stream water as the main output, ff N input by dry deposition and biological fixation and output by denitlification are taken into account, this subtropical forested watershed currently acts as a considerable sink for N, with a net sink ranging from 1.309 to 1.913 g N/（m2-yr） which may enhance carbon sequestration of the terrestrial ecosystem.
基金supported by the Special Fund for Agroscientific Research in the Public Interest in China (201303133, 201203031)the Key Technologies R&D Program of China during the 12th Five-Year Plan period (2011BAD16B14)+1 种基金the Construction of Modern Agricultural Industrial Technology System, Ministry of Agriculture, Chinathe Beijing Higher Education Young Elite Teacher Project, China (YETP0300)
文摘The photosynthetic characteristics of flag leaf and the accumulation and remobilization of pre-anthesis dry mass（DM） and nitrogen（N） in vegetable organs in nine wheat cultivars under different source-sink manipulation treatments including defoliation（DF）, spike shading（SS） and half spikelets removal（SR） were investigated. Results showed that the SS treatment increased the photosynthetic rate（Pn） of flag leaf in source limited cultivar, but had no significant effect on sink limited cultivar. The SR treatment decreased the Pn of flag leaf. Grain DM accumulation was limited by source in some cultivars, in other cultivars, it was limited by sink. Grain N accumulation was mainly limited by source supply. The contribution of pre-anthesis dry mass to grain yield from high to low was stem, leaf and chaff, while the contribution of pre-anthesis N to grain N from high to low was leaf, stem and chaff. Cultivars S7221 and TA9818 can increase the contribution of remobilization of DM and N to grain at the maximum ratio under reducing source treatments, which may be the major reason for these cultivars having lower decrease in grain yield and N content under reducing source treatments.
基金supported by the National Science & Technology Pillar Program(Grant No. 2011BAD31B03)the Special Project on Water Pollution Control by the National Science & Technology Pillar Program(Grant No. 2009ZX07104-002)
文摘Non-point-source pollution has become a major threat to the water quality of the Three Gorges Reservoir(TGR);however,nutrient loadings from terrestrial sources are unclear due to a lack of in situ monitoring.A representative small watershed in the central part of the TGR area was selected to monitor the loss of nitrogen(N) and phosphorous(P) continuously along with the runoff from 2007 through 2009 to understand the exact sources and loadings.Results show that the non-point-source nitrogen and phosphorus comes mainly from the storm runoff from residential areas,citrus orchards and sloping croplands,which contributes up to 76% of the loadings in this watershed.Thus,a crucial measure for controlling non-point-source pollution is to intercept storm runoff from the three sources.Paddy fields provide a sink for non-point-source N and P by intercepting the runoff and sediment along with their different forms of nitrogen and phosphorus.The N and P removal efficiency by paddy fields from residential areas is within the range of 56% to 98%.Paddy fields are an important land-use option for reducing the non-point-source loading of N and P in the TGR area.
基金supported by the Jiangsu Key Project of Science and Technology(BE2001331)National Key Project of Science and Technology,China(2002BA516A1).
文摘By removing panicles and spikelets, the effects of nitrogen supply-demand balance(NSDB)on nitrogen translocation and senescence of leaves at different positions of the same stem in rice plant were studied. The results showed that under NSDB<0(CK), nitrogen translocation and senescence of the top 4 leaves was normal. Nitrogen exported from the top leaves(LFT)especially the top 4 leaves decreased remarkably with increase of NSDB. thus, their MDA contents and differences in color(SPAD value)decreased, while the activities of SOD and CAT increased. Under NSDB>0(panicle removal), N accumulation of the top 4 leaves increased significantly, and the leaf senescence process was delayed. The results also indicated that the color of the 4th LFT was mainly affected by NSDB among the top 4 leaves and was lighter than the 3rd LFT when nitrogen supply was insufficient for the sink need.
基金supported by the National Key Technology Research and Development Program(Grant No.2013BAD07B12)the grant from Jiangxi Province(555 Talents Program)
文摘To study whether integrative fertilization [growing milk vetch in winter and reducing the dose of chemical nitrogen(N) fertilizer] can improve rice yield, and to reveal the underlying regulatory mechanisms for integrative fertilization, a three-year field trial including two treatments, milk vetch-rice-rice(MRR) and winter fallow-rice-rice(FRR), was conducted in 2010, 2011 and 2012.Our results demonstrated that the MRR treatment could significantly improve rice yield compared with the FRR treatment, especially when the application ratio of milk vetch and chemical fertilizer was 1:2.MRR treatment increased the effective panicle number and the spikelet number per panicle.In addition, a higher tillering number, leaf area index, photosynthetic-potential and photosynthetic-potential to grain ratio were observed in MRR treatment, which could provide enough dry matter for yield formation.Moreover, in MRR treatment, we discovered a higher transportation ratio and transformation ratio of dry matter in culm and leaves, and a stronger total sink capacity and spikelet-root bleeding intensity at the heading stage and 15 d after heading.Furthermore, the MRR treatment showed higher total N, phosphorus and potassium uptakes than FRR treatment, which was associated with the higher root dry weight in each soil layers.These results suggest that growing milk vetch in winter can improve rice yield under less chemical N fertilizer application, which is due to the improvement of soil nutrient status and the increased of rice root growth and development.
基金supported by the National Natural Science Foundation of China (30871482)the Scientific Research Innovation Project for Graduate Student of Jiangsu Province, China (CXO7B_184Z)
文摘Grain filling, a crucial stage of grain yield formation in rice, is usually affected by the panicle nitrogen （N） fertilization. Field and pot culture experiments were conducted to explore the underlying mechanisms of N effect. Two rice cultivars with high lodging resistance were grown in the field and pot. Four panicle N fertilization treatments were conducted in 2006 and repeated in 2007. The result showed that medium level of panicle N fertilization treatment （NM） enhanced the accumulation and translocation of non-structural carbohydrate （NSC） in the stem and sheath. Compared with non-nitrogen treatment （NO）, NM promoted the translocation of labeled ^13C from stem and sheath to grain. But, low level of panicle N fertilization treatment （NL） and high level of panicle N fertilization treatment （NH） showed the negative effect. The endosperm cell, grain length, and grain width of NM increased more quickly than that of NO from 4 to 10 d after anthesis. During the early period of grain filling, sucrose-phosphate synthase （EC 2.4.1.14, SPS） activity were significantly higher for the NM treatment than those of the NL and NH treatments. Sucrose synthase （EC 2.4.1.13, SuSase） activity in the grains was substantially enhanced by NM, with the duration of higher activity being longer than those of the other treatments. At maturing stage, NM significantly increased the filled grain number, the seed-setting rate, and the grain weight compared with NL and NH. The results suggest that NM have a positive effect on the activities of enzymes of physiological importance, thereby increasing the grain size and promoting grain filling.
