This paper is based on nutrient budget and its effects on soil nutrient status in typical greenhouse system in China to provide a basis for raising the utilization rate of fertilizers and maintaining the sustainable d...This paper is based on nutrient budget and its effects on soil nutrient status in typical greenhouse system in China to provide a basis for raising the utilization rate of fertilizers and maintaining the sustainable development of agriculture in the greenhouse.By investigating the management of 18 representative greenhouses in Shouguang,Shandong Province,China,and analyzing both the greenhouse and open field soil samples,the soil nutrient budget and the trend of nutrient accumulation and translocation in soils were thus studied.The results under greenhouse system showed that the average annual inputs of N,P2O5 and K2O were 4 088,3 655 and 3 437 kg ha-1,respectively.The total inputs of N,P2O5 and K2O provided by chemical fertilizers which are the main source of soil nutrient were 63,61 and 66%,respectively.The utilization rates of N,P2O5 and K2O were only 24,8,46% and the input ratio among N,P2O5 and K2O (1:0.9:0.8) was quite different from the uptake ratio (1:0.3:1.4).It had caused the excess of N,P2O5 and K2O in the soil,and the theoretical surpluses were 3 214,3 401 and 2 322 kg ha-1,respectively,for N,P2O5 and K2O.The level of the organic matter,total nitrogen,nitrate nitrogen,available phosphorus,and available potassium was increased substantially,and their maximum level was observed in the topsoil (0-20 cm) with an average value being 1.4,1.9,21.2,5.4,and 3.7 times higher than that of the open field soil,respectively.The greenhouse soils showed leaching of the nutrients,especially NO3- which would cause a potential risk to the quality of groundwater in the area.It is necessary to apply more organic manure and provide nutrients according to the crop requirements and soil fertility as it could not only produce high crop yield,but also be beneficial to balance the soil nutrient and improve the utilization rate of fertilizers.Further,there would be no significant surplus of nutrients which may leach out of soil to contaminate the environment.展开更多
This study was to evaluate the effect of stocking densities on the nitrogen and phosphorus budgets for a polyculture of the crab Portunus trituberculatus and the Pacific white shrimp Litopenaeus vannamei.The shrimps(i...This study was to evaluate the effect of stocking densities on the nitrogen and phosphorus budgets for a polyculture of the crab Portunus trituberculatus and the Pacific white shrimp Litopenaeus vannamei.The shrimps(initial weight,0.012 g)were cultured at a density of 45 shrimp m^(-2),and juvenile crabs(initial weight,0.024 g)were cultured at five densities of 0,3,6,9,and 12 crabs m^(-2).The treatments were grouped as C0S45,C3S45,C6S45,C9S45,and C12S45,respectively.Water quality parameters,growth of shrimp and crabs,and nitrogen and phosphorus budget were measured.The results indicated that the shrimp performances in polyculture treatments C3S45 and C6S45 were superior to those in the crab-free treatment(C0S45).The crab in treatments C3S45 and C6S45 exhibited a significantly higher final mean weight and carapace width/length than those in treatments C9S45 and C12S45.The final size and survival of crabs had a negative correlation with the increasing crab stocking density.The contents of total phos-phorus and total nitrogen and the comprehensive contamination index values were higher in the C9S45 and C12S45 treatments than in the other treatments.The conversion ratios of nitrogen for crab and shrimp growth in treatment C3S45 were significantly higher than those in the crab-free treatment.These findings indicate that polyculturing shrimp with crabs at suitable densities can improve productivity,profitability,nutrient utilization,and the environmental quality.From the 60-day treatments,the optimal culture densi-ties were 3-6 crabs m^(-2) and 45 shrimps m^(-2).展开更多
Based on a hydrodynamic-ecological model, the temperature, salinity, current, phytoplankton(Chl a),zooplankton, and nutrient(dissolved inorganic nitrogen, DIN, and dissolved inorganic phosphorous, DIP)distributions in...Based on a hydrodynamic-ecological model, the temperature, salinity, current, phytoplankton(Chl a),zooplankton, and nutrient(dissolved inorganic nitrogen, DIN, and dissolved inorganic phosphorous, DIP)distributions in the Beibu Gulf were simulated and the nutrient budget of 2015 was quantitatively analyzed. The simulated results show that interface processes and monsoons significantly influence the ecological processes in the gulf. The concentrations of DIN, DIP, phytoplankton and zooplankton are generally higher in the eastern and northern gulf than that in the western and southern gulf. The key regions affected by ecological processes are the Qiongzhou Strait in winter and autumn and the estuaries along the Guangxi coast and the Red River in summer.In most of the studied domains, biochemical processes contribute more to the nutrient budget than do physical processes, and the DIN and DIP increase over the year. Phytoplankton plays an important role in the nutrient budget;phytoplankton photosynthetic uptake is the nutrient sink, phytoplankton dead cellular release is the largest source of DIN, and phytoplankton respiration is the largest source of DIP. The nutrient flux in the connected sections of the Beibu Gulf and open South China Sea(SCS) inflows from the east and outflows to the south. There are 113 709 t of DIN and 5 277 t of DIP imported from the open SCS to the gulf year-around.展开更多
This study was performed to evaluate the effect of temperature on the carbon(C),nitrogen(N),and phosphorus(P)nu-trient budgets of adult steelhead trout(Oncorhynchus mykiss)with different body sizes.A complete two-fact...This study was performed to evaluate the effect of temperature on the carbon(C),nitrogen(N),and phosphorus(P)nu-trient budgets of adult steelhead trout(Oncorhynchus mykiss)with different body sizes.A complete two-factor experiment was con-ducted at four temperatures,i.e.,9(T9),13(T13),16(T1℃℃℃6),and 19(T19);and three body sizes,℃i.e.,0.65 kg±0.02 kg(S1),1.22 kg±0.06 kg(S2),and 2.05 kg±0.09 kg(S3).The following properties of steelhead trout were determined:C,N,and P nutrient budgets;feed intake rate;fecal production rate;oxygen consumption rate;ammonia excretion rate;phosphorus excretion rate;scope of the growth of C,N,and P;and absorption efficiency of C,N,and P.Results showed no significant interaction between temperature and body size in terms of the nutrient budgets of steelhead trout.However,temperature and body size played important separate roles in the nutrient budgets except for the absorption efficiency of nitrogen.The feed intake rate,fecal production rate,ammonia excretion rate,phosphorus excretion rate,and scope of the growth of C,N,and P were the highest in the T16 treatments.The absorption effi-ciency of C and P decreased as temperature increased.Nonlinear multiple regression results indicated that 15 was the approximate℃optimal temperature for the feeding and growth of steelhead trout.The feed intake rate,fecal production rate,oxygen consumption rate,ammonia excretion rate,phosphorus excretion rate,and scope of the growth of C,N,and P per unit of the body weight of fish decreased as body size increased.The absorption efficiency of C increased as body weight increased,and the absorption efficiencies of P in the S2 and S3 treatments were significantly higher than those in the S1 treatment.During the culture of steelhead trout,the daily ratio should be adjusted with changes in the temperature and body size of fish.Furthermore,managers should focus on the risk of hypoxia at high water temperatures.展开更多
Over the past four periods ( 1959--1960, 1982--1983, 1992--1993, and 1998--1999), the ecosystem of the Bohai Sea changed due to both a significant decrease of river water discharge from the Huanghe River and a reduc...Over the past four periods ( 1959--1960, 1982--1983, 1992--1993, and 1998--1999), the ecosystem of the Bohai Sea changed due to both a significant decrease of river water discharge from the Huanghe River and a reduction of precipitation. The shifts in nutrient chemistry could result in changes in the phytoplankton composition with an increased potential for non-diatom algal blooms. Simple box model was used to estimate the water - mass balance and nutrient budgets for the Bohai Sea. Water budgets indicate that the residual flow changed from out of the Bohai Sea before 1993, but became inflow to the Bohai Sea after then. The nutrient budgets developed indicate that the Bohai Sea was a sink for nutrients except for phosphate in 1959--1960 and 1982-- 1983 and for silicate in 1982--1983. Net water flow transports nutrients out of the Bohai Sea in 1959--1960, 1982--1983 and 1992--1993, but into the sea in 1998--1999 due to climate changes, such as precipitation and subsequent freshwater discharge. The residual fluxes of nutrients are minor relative to atmospheric deposition and riverine inputs. Conversions of phosphate values to carbon by stoichiometric ratios were used to predict that the system was net heterotrophic before 1982--1983 and net autotrophic after then. Nutrient budgets can explain the change of nutrient concentrations in the Bohai Sea except nitrates, which should include the surface runoff.展开更多
The objective of the study was to establish approximate relationships between yield and soil nutrients in oil palm production. The study was conducted in Nigerian Institute for Oil Palm Research (NIFOR) substation Ibe...The objective of the study was to establish approximate relationships between yield and soil nutrients in oil palm production. The study was conducted in Nigerian Institute for Oil Palm Research (NIFOR) substation Ibesit ekoi in Oruk Anam Local Government Area of Akwa Ibom State Nigeria. Soil, rainfall and yield data were collected from oil palm plantation established 49, 29, 9 and 0 (control) years ago in an area underlain by coastal plain sands. Descriptive statistics, analysis of variance and multiple stepwise regression analysis were used to study variations, effect of land use on soil properties at different depths and contributions of various soil nutrients at different depths to the yield (fresh fruit bunch ‘FFB’ and palm oil) of oil palm. Results of coefficient of variability revealed that approx. 45.5% of the variables were highly variable including available phosphorus, extractable zinc, FFB and palm oil, while others were either least or moderately variable. Oil palm trees influenced soil development with its effect on silt content at 30 - 60 cm depth. Uptake of phosphorus in oil palm land use system decreases with depth. This was further confirmed by the relative contribution of available phosphorus to FFB yield that decreased from the surface of the soil downwards. Extractable zinc contents of oil palm land use were not significantly different from each other (ranging between 9.65 and 7.84 mg·kg–1) but significantly different from the control (23.99 mg·kg–1). In the modeling process, it was observed that the absolute contribution of texture was minimal while exchangeable sodium was highest (i.e. 66.5 percent) in the quantity of oil palm production. Also extractable copper and zinc were found to have made large contributions to FFB and oil palm. Oil palm (Elaeis guineensis) is a high-yielding source of edible and technical oils but requires proper knowledge and precise administration of nutrient demands for management of a major production constraint which is soil fertility.展开更多
The environmental problems in the Bohai Sea have become more serious in the last decade. High nutrient concentration contributes much to it. A Sino-German cooperation program has been carried out to improve the unders...The environmental problems in the Bohai Sea have become more serious in the last decade. High nutrient concentration contributes much to it. A Sino-German cooperation program has been carried out to improve the understanding of the ecosystem by observations and modelling. A three-dimensional ecosystem model, coupled with a physical transport model, is adopted in this study. The simulation for the year 1982 is validated by the data collected in 1982/1983. The simulated annual mean nutrient concentrations are in good agreement with observations. The nutrient concentrations in the Bohai Sea, which are crucial to the algal growth, are high in winter and low in summer. There are depletion from spring to summer and elevation from autumn to winter for nutrients. The nutrients’ depletion is a response to the consumption of the phytoplankton bloom in spring. Internal recycle and external compensation affect the nutrient cycle. Their contributions to the nutrient budgets are discussed based on the simulated results. Production and respiration are the most important sink and source of nutrients. The process of photosynthesis consumes 152 kilotons-P and 831.1 kilotons-N while respiration releases 94.5 kilotons-P and 516.6 kilotons-N in the same period. The remineralization of the detritus pool is an important source of nutrient regene- ration. It can compensate 23 percent of the nutrient consumed by the production process. The inputs of phosphates and nitrogen from rivers are 0.55 and 52.7 kilotons respectively. The net nutrient budget is -3.05 kilotons-P and 31.6 kilotons-N.展开更多
The Bohai Rim region is one the most important bases for commodity grain production in China. With the rapid pace of agricultural industrialization, nitrogenous fertilizer has been used at an ever increasing rate, whi...The Bohai Rim region is one the most important bases for commodity grain production in China. With the rapid pace of agricultural industrialization, nitrogenous fertilizer has been used at an ever increasing rate, which resulted in the trace of accumulative nitrogen in the soil and caused serious environmental problems. In this study we made use of the farmland nitrogen balance model to assess the spatial difference of farmland nitrogen nutrient budget in the Bohai Rim region in 2008 with the assistance of GIS. Our results indicated that: 1) Farmland in this region has a nitrogen surplus totaling 5.0822 million tons, or an average of 288.54 kg/ha. 2) In the Bohai Rim region, farmland nitrogen input and farmland nitrogen budget both show a spatial differentiation. Major grain-producing areas have a higher nitrogen input than that of the grazing-farming areas. The main sources of nitrogen input include chemical fertilizer, organic fertilizer, deposition from atmospheric drying and wetting, and biological fixation, which account for 79.47%, 9.53%, 4.62%, and 3.58% of the total input, respectively. Therefore, chemical fertilizer is the predominant source of nitrogen input to farmland. 3) A total of 3.3398 million tons of nitrogen were output from the farmland via harvested crops and it accounts for 52.36% of the total nitrogen output from farmland in this region. On average, the amount of nitrogen output from unit farmland is equal to 176.65kg/ha. This study has shed light on farmland nitrogen budget and its spatial variation in the study area, may provide scientific evidences for rationalizing the use of chemical fertilizer and managing agricultural operation on the regional scale and is also valuable for improving the economic and ecological efficiency of fertilizer use at the regional scale.展开更多
To estimate nutrient budgets,water samples were collected at 16 sites in Tapong lagoon from January 2004 through April 2005 and the parameters of water quality were analyzed immediately after collection.These data wer...To estimate nutrient budgets,water samples were collected at 16 sites in Tapong lagoon from January 2004 through April 2005 and the parameters of water quality were analyzed immediately after collection.These data were used to build a box model for calculating nutrient budgets of the lagoon.We estimated the net amount of nutrient fluxes into (coming from creeks) and out (from tidal inlet) of the lagoon and calculated the total amount of nutrient that deposits into the sediment in a full tidal cycle.During January and April,nutrients (including nitrate,nitrite and ammonia) accumulated in the lagoon,but phosphate,total phosphate and suspended solids were flushed out of the lagoon from the tidal inlet.In addition,a huge amount of suspended solids (13-15 tons per tidal cycle) flew from the lagoon to the adjacent ocean through the inlet-outlet channel.展开更多
基金supported by the State Key Program of National Natural Science of China (30230250)
文摘This paper is based on nutrient budget and its effects on soil nutrient status in typical greenhouse system in China to provide a basis for raising the utilization rate of fertilizers and maintaining the sustainable development of agriculture in the greenhouse.By investigating the management of 18 representative greenhouses in Shouguang,Shandong Province,China,and analyzing both the greenhouse and open field soil samples,the soil nutrient budget and the trend of nutrient accumulation and translocation in soils were thus studied.The results under greenhouse system showed that the average annual inputs of N,P2O5 and K2O were 4 088,3 655 and 3 437 kg ha-1,respectively.The total inputs of N,P2O5 and K2O provided by chemical fertilizers which are the main source of soil nutrient were 63,61 and 66%,respectively.The utilization rates of N,P2O5 and K2O were only 24,8,46% and the input ratio among N,P2O5 and K2O (1:0.9:0.8) was quite different from the uptake ratio (1:0.3:1.4).It had caused the excess of N,P2O5 and K2O in the soil,and the theoretical surpluses were 3 214,3 401 and 2 322 kg ha-1,respectively,for N,P2O5 and K2O.The level of the organic matter,total nitrogen,nitrate nitrogen,available phosphorus,and available potassium was increased substantially,and their maximum level was observed in the topsoil (0-20 cm) with an average value being 1.4,1.9,21.2,5.4,and 3.7 times higher than that of the open field soil,respectively.The greenhouse soils showed leaching of the nutrients,especially NO3- which would cause a potential risk to the quality of groundwater in the area.It is necessary to apply more organic manure and provide nutrients according to the crop requirements and soil fertility as it could not only produce high crop yield,but also be beneficial to balance the soil nutrient and improve the utilization rate of fertilizers.Further,there would be no significant surplus of nutrients which may leach out of soil to contaminate the environment.
基金supported by the National Key Technology Research and Development Program of Chi-na for the Eleventh Five-Year Plan(No.2006BAD09A01).
文摘This study was to evaluate the effect of stocking densities on the nitrogen and phosphorus budgets for a polyculture of the crab Portunus trituberculatus and the Pacific white shrimp Litopenaeus vannamei.The shrimps(initial weight,0.012 g)were cultured at a density of 45 shrimp m^(-2),and juvenile crabs(initial weight,0.024 g)were cultured at five densities of 0,3,6,9,and 12 crabs m^(-2).The treatments were grouped as C0S45,C3S45,C6S45,C9S45,and C12S45,respectively.Water quality parameters,growth of shrimp and crabs,and nitrogen and phosphorus budget were measured.The results indicated that the shrimp performances in polyculture treatments C3S45 and C6S45 were superior to those in the crab-free treatment(C0S45).The crab in treatments C3S45 and C6S45 exhibited a significantly higher final mean weight and carapace width/length than those in treatments C9S45 and C12S45.The final size and survival of crabs had a negative correlation with the increasing crab stocking density.The contents of total phos-phorus and total nitrogen and the comprehensive contamination index values were higher in the C9S45 and C12S45 treatments than in the other treatments.The conversion ratios of nitrogen for crab and shrimp growth in treatment C3S45 were significantly higher than those in the crab-free treatment.These findings indicate that polyculturing shrimp with crabs at suitable densities can improve productivity,profitability,nutrient utilization,and the environmental quality.From the 60-day treatments,the optimal culture densi-ties were 3-6 crabs m^(-2) and 45 shrimps m^(-2).
基金The National Key Research and Development Program of China under contract No.2017YFC1404801the Program of Xiamen Southern Oceanographic Center under contract No.15PZB009NF05。
文摘Based on a hydrodynamic-ecological model, the temperature, salinity, current, phytoplankton(Chl a),zooplankton, and nutrient(dissolved inorganic nitrogen, DIN, and dissolved inorganic phosphorous, DIP)distributions in the Beibu Gulf were simulated and the nutrient budget of 2015 was quantitatively analyzed. The simulated results show that interface processes and monsoons significantly influence the ecological processes in the gulf. The concentrations of DIN, DIP, phytoplankton and zooplankton are generally higher in the eastern and northern gulf than that in the western and southern gulf. The key regions affected by ecological processes are the Qiongzhou Strait in winter and autumn and the estuaries along the Guangxi coast and the Red River in summer.In most of the studied domains, biochemical processes contribute more to the nutrient budget than do physical processes, and the DIN and DIP increase over the year. Phytoplankton plays an important role in the nutrient budget;phytoplankton photosynthetic uptake is the nutrient sink, phytoplankton dead cellular release is the largest source of DIN, and phytoplankton respiration is the largest source of DIP. The nutrient flux in the connected sections of the Beibu Gulf and open South China Sea(SCS) inflows from the east and outflows to the south. There are 113 709 t of DIN and 5 277 t of DIP imported from the open SCS to the gulf year-around.
基金funded by the National Key Research and Development Program of China(No.2019YFD0901000)the National Natural Science Foundation of China(No.31872575)the Key Research and Development Program of Shandong Province(No.2021SFGC0701).
文摘This study was performed to evaluate the effect of temperature on the carbon(C),nitrogen(N),and phosphorus(P)nu-trient budgets of adult steelhead trout(Oncorhynchus mykiss)with different body sizes.A complete two-factor experiment was con-ducted at four temperatures,i.e.,9(T9),13(T13),16(T1℃℃℃6),and 19(T19);and three body sizes,℃i.e.,0.65 kg±0.02 kg(S1),1.22 kg±0.06 kg(S2),and 2.05 kg±0.09 kg(S3).The following properties of steelhead trout were determined:C,N,and P nutrient budgets;feed intake rate;fecal production rate;oxygen consumption rate;ammonia excretion rate;phosphorus excretion rate;scope of the growth of C,N,and P;and absorption efficiency of C,N,and P.Results showed no significant interaction between temperature and body size in terms of the nutrient budgets of steelhead trout.However,temperature and body size played important separate roles in the nutrient budgets except for the absorption efficiency of nitrogen.The feed intake rate,fecal production rate,ammonia excretion rate,phosphorus excretion rate,and scope of the growth of C,N,and P were the highest in the T16 treatments.The absorption effi-ciency of C and P decreased as temperature increased.Nonlinear multiple regression results indicated that 15 was the approximate℃optimal temperature for the feeding and growth of steelhead trout.The feed intake rate,fecal production rate,oxygen consumption rate,ammonia excretion rate,phosphorus excretion rate,and scope of the growth of C,N,and P per unit of the body weight of fish decreased as body size increased.The absorption efficiency of C increased as body weight increased,and the absorption efficiencies of P in the S2 and S3 treatments were significantly higher than those in the S1 treatment.During the culture of steelhead trout,the daily ratio should be adjusted with changes in the temperature and body size of fish.Furthermore,managers should focus on the risk of hypoxia at high water temperatures.
基金The Ministry of Education of China under contract No. NCET-05 -0593special funds from the National Key Basic Research Program of China under contract No.2006CB400602Chinese Natural Sciences Foundation under contract No.40730847
文摘Over the past four periods ( 1959--1960, 1982--1983, 1992--1993, and 1998--1999), the ecosystem of the Bohai Sea changed due to both a significant decrease of river water discharge from the Huanghe River and a reduction of precipitation. The shifts in nutrient chemistry could result in changes in the phytoplankton composition with an increased potential for non-diatom algal blooms. Simple box model was used to estimate the water - mass balance and nutrient budgets for the Bohai Sea. Water budgets indicate that the residual flow changed from out of the Bohai Sea before 1993, but became inflow to the Bohai Sea after then. The nutrient budgets developed indicate that the Bohai Sea was a sink for nutrients except for phosphate in 1959--1960 and 1982-- 1983 and for silicate in 1982--1983. Net water flow transports nutrients out of the Bohai Sea in 1959--1960, 1982--1983 and 1992--1993, but into the sea in 1998--1999 due to climate changes, such as precipitation and subsequent freshwater discharge. The residual fluxes of nutrients are minor relative to atmospheric deposition and riverine inputs. Conversions of phosphate values to carbon by stoichiometric ratios were used to predict that the system was net heterotrophic before 1982--1983 and net autotrophic after then. Nutrient budgets can explain the change of nutrient concentrations in the Bohai Sea except nitrates, which should include the surface runoff.
文摘The objective of the study was to establish approximate relationships between yield and soil nutrients in oil palm production. The study was conducted in Nigerian Institute for Oil Palm Research (NIFOR) substation Ibesit ekoi in Oruk Anam Local Government Area of Akwa Ibom State Nigeria. Soil, rainfall and yield data were collected from oil palm plantation established 49, 29, 9 and 0 (control) years ago in an area underlain by coastal plain sands. Descriptive statistics, analysis of variance and multiple stepwise regression analysis were used to study variations, effect of land use on soil properties at different depths and contributions of various soil nutrients at different depths to the yield (fresh fruit bunch ‘FFB’ and palm oil) of oil palm. Results of coefficient of variability revealed that approx. 45.5% of the variables were highly variable including available phosphorus, extractable zinc, FFB and palm oil, while others were either least or moderately variable. Oil palm trees influenced soil development with its effect on silt content at 30 - 60 cm depth. Uptake of phosphorus in oil palm land use system decreases with depth. This was further confirmed by the relative contribution of available phosphorus to FFB yield that decreased from the surface of the soil downwards. Extractable zinc contents of oil palm land use were not significantly different from each other (ranging between 9.65 and 7.84 mg·kg–1) but significantly different from the control (23.99 mg·kg–1). In the modeling process, it was observed that the absolute contribution of texture was minimal while exchangeable sodium was highest (i.e. 66.5 percent) in the quantity of oil palm production. Also extractable copper and zinc were found to have made large contributions to FFB and oil palm. Oil palm (Elaeis guineensis) is a high-yielding source of edible and technical oils but requires proper knowledge and precise administration of nutrient demands for management of a major production constraint which is soil fertility.
基金supported by the National Natural Science Foundation of China with Grant(No.G497901001)the Major State Basic Research Program with Grant(No.G1999043703)
文摘The environmental problems in the Bohai Sea have become more serious in the last decade. High nutrient concentration contributes much to it. A Sino-German cooperation program has been carried out to improve the understanding of the ecosystem by observations and modelling. A three-dimensional ecosystem model, coupled with a physical transport model, is adopted in this study. The simulation for the year 1982 is validated by the data collected in 1982/1983. The simulated annual mean nutrient concentrations are in good agreement with observations. The nutrient concentrations in the Bohai Sea, which are crucial to the algal growth, are high in winter and low in summer. There are depletion from spring to summer and elevation from autumn to winter for nutrients. The nutrients’ depletion is a response to the consumption of the phytoplankton bloom in spring. Internal recycle and external compensation affect the nutrient cycle. Their contributions to the nutrient budgets are discussed based on the simulated results. Production and respiration are the most important sink and source of nutrients. The process of photosynthesis consumes 152 kilotons-P and 831.1 kilotons-N while respiration releases 94.5 kilotons-P and 516.6 kilotons-N in the same period. The remineralization of the detritus pool is an important source of nutrient regene- ration. It can compensate 23 percent of the nutrient consumed by the production process. The inputs of phosphates and nitrogen from rivers are 0.55 and 52.7 kilotons respectively. The net nutrient budget is -3.05 kilotons-P and 31.6 kilotons-N.
基金National Natural Sciences Foundation of China,No.41130748No.41101162Basic Research Work of Central Scientific Research Institution for Public Welfare,No.202-18
文摘The Bohai Rim region is one the most important bases for commodity grain production in China. With the rapid pace of agricultural industrialization, nitrogenous fertilizer has been used at an ever increasing rate, which resulted in the trace of accumulative nitrogen in the soil and caused serious environmental problems. In this study we made use of the farmland nitrogen balance model to assess the spatial difference of farmland nitrogen nutrient budget in the Bohai Rim region in 2008 with the assistance of GIS. Our results indicated that: 1) Farmland in this region has a nitrogen surplus totaling 5.0822 million tons, or an average of 288.54 kg/ha. 2) In the Bohai Rim region, farmland nitrogen input and farmland nitrogen budget both show a spatial differentiation. Major grain-producing areas have a higher nitrogen input than that of the grazing-farming areas. The main sources of nitrogen input include chemical fertilizer, organic fertilizer, deposition from atmospheric drying and wetting, and biological fixation, which account for 79.47%, 9.53%, 4.62%, and 3.58% of the total input, respectively. Therefore, chemical fertilizer is the predominant source of nitrogen input to farmland. 3) A total of 3.3398 million tons of nitrogen were output from the farmland via harvested crops and it accounts for 52.36% of the total nitrogen output from farmland in this region. On average, the amount of nitrogen output from unit farmland is equal to 176.65kg/ha. This study has shed light on farmland nitrogen budget and its spatial variation in the study area, may provide scientific evidences for rationalizing the use of chemical fertilizer and managing agricultural operation on the regional scale and is also valuable for improving the economic and ecological efficiency of fertilizer use at the regional scale.
基金supported by "Dapeng Bay National Science Area Administration"
文摘To estimate nutrient budgets,water samples were collected at 16 sites in Tapong lagoon from January 2004 through April 2005 and the parameters of water quality were analyzed immediately after collection.These data were used to build a box model for calculating nutrient budgets of the lagoon.We estimated the net amount of nutrient fluxes into (coming from creeks) and out (from tidal inlet) of the lagoon and calculated the total amount of nutrient that deposits into the sediment in a full tidal cycle.During January and April,nutrients (including nitrate,nitrite and ammonia) accumulated in the lagoon,but phosphate,total phosphate and suspended solids were flushed out of the lagoon from the tidal inlet.In addition,a huge amount of suspended solids (13-15 tons per tidal cycle) flew from the lagoon to the adjacent ocean through the inlet-outlet channel.