Nutrient Budget and Soil Nutrient Status in Greenhouse System

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.

Production of Pacific White Shrimp Polycultured with Swimming Crab at Different Densities, and Nutrient Budget in the Enclosure System

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).

Effect of Temperature on the Carbon, Nitrogen, and Phosphorus Nutrient Budgets of Steelhead Trout (Oncorhynchus mykiss) with Different Sizes

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.

Analysis of the spatial and temporal distributions of ecological variables and the nutrient budget in the Beibu Gulf

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.

Historic changes in flux of matter and nutrient budgets in the Bohai Sea

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.

Nutrient Budget for Optimal Oil Palm (<i>Elaeis guineensis</i>Jacq) Yield on Coastal Plain Sands Soils of Akwa Ibom State Nigeria

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.

A study on the spatial difference of farmland nitrogen nutrient budget in the Bohai Rim region, China

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.

Annual Cycle and Budgets of Nutrients in the Bohai Sea

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.

Estimating nutrient budgets in a coastal lagoon

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.

Nitrogen and phosphorus budgets of the Changjiang River estuary

Eutrophication has emerged as a key environmental problem in Chinese coastal waters, especially in the Changjiang (Yangtze) River estuary. In this area, large nutrient inputs result in frequent harmful algal blooms and serious hypoxia in bottom waters. Four cruises were made in the estuary in 2006 to assess the concentration and distribution of dissolved inorganic nitrogen (DIN) and phosphorus (DIP). The concentration of DIN decreased gradually in a linear relationship with salinity from the river mouth to outer waters, while DIP was relatively more dispersed. A modified box budget method was used to estimate nutrient fluxes in the estuary and its adjacent waters. Water and nutrient budgets as well as primary production and denitrification rates were estimated from the box budget model. Estimated water residence time in the estuary was about 11 d. The turbid mixing zone released 33% of DIN and 49% of DIP, while in the adjacent outer sea 17.9 mmol DIN/m2·d and 0.36 mmol DIP/m2·d were fixed. Dissolved inorganic phosphorus was imported from the deep open sea waters, supporting primary production and population growth in this zone. Net ecosystem production (NEP) was calculated at 38.2 mmol/m2·d in the outer estuary and the estimated rate (N-fixation minus denitrification) was negative (1.92 mmol/m2·d), implying that a large amount of input nitrogen was taken up by algae and recycled through denitrification in bottom water and sediment.

温度对虹鳟幼鱼碳、氮、磷营养元素收支的影响

为探讨海水环境下温度对虹鳟(Oncorhynchus mykiss)幼鱼碳(C)、氮(N)、磷(P)营养元素收支的影响,选取体质量为(91.40±13.63)g的虹鳟幼鱼进行海水驯化后,设置4个温度水平(7、11、15、19℃)进行养殖,并测定不同温度处理组的虹鳟幼鱼C、N、P营养元素的收支情况。结果显示:虹鳟幼鱼的摄食率、排粪率、排氨率、排磷率在7℃处理组中分别为0.599mg·(g·h)^(-1)、0.120mg·(g·h)^(-1)、4.757μg·(g·h)^(-1)、0.510μg·(g·h)^(-1),显著低于其他温度处理组(P<0.05);在15℃处理组中达到最大值,分别为1.103mg·(g·h)^(-1)、0.185mg·(g·h)^(-1)、8.953μg·(g·h)^(-1)、0.821μg·(g·h)^(-1)。虹鳟幼鱼的耗氧率随温度升高而逐渐增加,在19℃处理组达到最大值,为378.006μg·(g·h)^(-1)。C、N、P营养元素的生长余力在7℃处理组最低;在15℃处理组中达到最大且显著高于其他各组(P<0.05)。C、N、P营养元素的吸收效率19℃处理组显著低于其他温度处理组(P<0.05);在15℃处理组中达到最大值,分别为61.38%、85.27%、71.54%。研究结果表明,15℃是海水环境下虹鳟幼鱼C、N、P营养元素收支最旺盛的温度,过高的温度不利于虹鳟幼鱼各营养元素的收支。

渤海氮磷营养盐的循环和收支

近年来无机氮与活性磷酸盐已成为渤海主要的污染物质 .为了解氮、磷营养盐的循环规律 ,建立了一个生物、物理耦合的三维生态模型 ,模拟了渤海氮磷营养盐循环 ,估算了它们的收支情况 .渤海营养盐浓度从春季到夏季下降 ,秋季到冬季上升 ,4～ 9月为消耗期 ,1 0～ 3月为补充期 .磷酸盐冬季最高值位于渤海湾 ,辽东湾西北部全年都维持了比较高的浓度 ;无机氮的高值区始终位于莱州湾黄河口附近 .光合作用和呼吸作用是营养盐最大的源和汇 ,碎屑的矿化可以补充光合作用消耗的营养盐的 30 % .河流输入每年可以补充P 0 5 5× 1 0 3t和N 5 2 7×1 0

温室栽培系统的养分平衡及土壤养分变化特征

【目的】弄清中国典型地区温室栽培系统的养分收支状况及其对土壤养分累积变化的影响,为节肥增效,实现温室生产的可持续发展提供依据。【方法】选取中国典型温室栽培地区山东寿光具有代表性的18个温室大棚为研究对象,通过对各温室肥料投入、作物种类及产量等情况的详细调查及土壤分析,研究温室系统养分的收支平衡及土壤养分变化特征。【结果】(1)在中国典型温室栽培生产基地,每年氮、磷、钾养分的平均投入量为4088、3656和3438kg.hm-2,其中随化肥投入的氮、磷、钾养分分别占到各养分总量的63%、61%和66%,是土壤养分的主要来源。(2)温室栽培条件下,氮、磷、钾养分的利用率分别仅为24%、8%、46%,且施用比例(1﹕0.9﹕0.8)与作物的需求比例(1﹕0.3﹕1.4)严重失衡。温室土壤有机质相对缺乏,而氮、磷、钾则大量累积,其理论盈余量分别为3214、3401和2322kg.hm-2。(3)温室土壤有机质、全氮、硝态氮、速效磷、速效钾的含量均显著高于露地土壤,且耕层(0—20cm)的累积量最高,其平均含量分别为露地土壤的1.4倍、1.9倍、21.2倍、5.4倍和3.7倍。各养分在土壤剖面存在不同程度的向下迁移现象,其中NO3-的大量累积和向下迁移是造成当地地下水污染风险的关键因子。【结论】温室栽培系统中,盲目过量的施肥,不仅造成肥料资源的浪费,破坏土壤-植物的养分供需平衡,影响蔬菜品质,同时氮、磷的随水淋失也会带来巨大的环境风险。温室生产中不仅应重视高质量有机肥的投入,还应根据作物的需肥特性及土壤供肥能力进行计量施肥,以实现温室生产高效、优质、环境友好的发展目标。

我国不同区域农田养分平衡对土壤肥力时空演变的影响

区域农田养分盈亏是驱动农田土壤肥力时空变化的主要因素。对我国6个农业生态试验站(海伦、沈阳、栾城、长武、常熟、鹰潭)站区农田土壤肥力在近年来时空演变的研究表明,除了海伦站黑土和常熟站水稻土的有机质和全氮平均含量下降外,其他站区均呈现增加趋势,主要原因是黑土和乌栅土有机质和全氮含量较高,目前农田有机C和N投入水平无法维持其平衡;6个站区土壤速效磷有增有减,而土壤速效钾除了栾城和鹰潭站区域外均呈降低趋势。从站区农田养分的年平衡与土壤养分的年变化量关系看,农田氮、磷、钾的盈亏量决定了土壤养分的变化方向。土壤有机碳和全氮的初始含量过高(分别超过15.1 g/kg和1.60 g/kg)时,也会导致其年际间的变化方向从增加变为降低。农田氮素盈亏量与土壤全氮变化量之间相关不显著,主要是由于化肥投入和作物籽粒输出的农田氮平衡不能完全代表土壤氮素的真实盈亏情况;而农田磷素和钾素的盈亏量与土壤速效磷和速效钾的年变化量的显著相关。

黑土长期施肥及养分循环再利用的作物产量及土壤肥力质量变化Ⅲ.土壤养分收支

计算了 1985～ 1999年试验期间各模拟施肥模型的作物移出养分量和施肥输入养分量 .结果表明 ,施用N肥可加剧土壤P收支赤字 ,而施用N、P肥则加剧土壤K收支赤字 .实验展示了我国在 2 0世纪70年代大面积贫P土壤和 80年代大面积缺K土壤出现的原因 .保持养分循环再利用可缓解土壤养分收支赤字 ,但不能满足丰产作物的养分需求 .在保持养分循环利用基础上根据土壤肥力适当施用化肥 ,可满足丰产作物的养分需求和平衡土壤养分收支 ,不致发生大量过剩N进入环境 .

下辽河平原农业生态系统不同施肥制度的土壤养分收支

本试验是在潮棕壤上进行了 10年的定位试验 .研究了在养分循环再利用的基础上采取不同施肥制度下作物养分移出量 ,并结合施肥量计算出土壤中N、P、K养分收支 .结果表明 ,在保持农业系统养分循环再利用的基础上 ,根据养分供给力设计化肥施用量 ,不仅可实现作物高产 ,而且可平衡土壤养分收支 ,避免土壤中肥料养分过剩 (主要是N)进入环境 .并揭示了我国在 2 0世纪 70年代以前大面积农田土壤缺P和 80年代农田土壤大面积缺K的原因 .

不同施肥模式对下辽河平原水稻生态系统生产力及养分收支的影响

采用田间肥料试验,研究了不同施肥模式对稻田生态系统的生产力和养分收支的影响。结果表明:随养分配施均衡程度的增加,系统的生产力逐渐提高,其中氮磷钾处理的生产力最高;氮肥对水稻生产力的贡献最大(对生物量的贡献约20%,对籽实产量的贡献约34%),磷肥和钾肥的贡献相当;在水稻各部位对氮、磷、钾养分的吸收中,氮的吸收主要集中在籽实和秸秆中,磷的吸收则主要集中在籽实中,钾的吸收主要集中在秸秆中;在各施肥处理中,土壤全量养分和有机质的变化不大,而速效养分的变化较大,特别是速效磷库和速效氮库;单施化肥处理的土壤,其速效养分含量不高,而施有机肥处理土壤的速效养分含量较高,表明有机肥较有利于土壤养分的积累。

黄海氮磷营养盐的循环和收支研究

建立了一个生物-物理耦合的三维营养盐动力学模型,模拟了黄海无机氮、活性磷酸盐和叶绿素a的年循环规律,估算了黄海营养盐的收支情况和季节差异,并将数值结果与实测资料进行比较。结果表明:黄海无机氮和无机磷经历了春、夏的消耗及秋、冬的补充,维持了黄海全年较高的生产力,年平均初级生产力达508mgC·m-2·d-1。黄海水文环境在很大程度上影响着营养盐的分布和生态功能:黄海中部深水区季节性热层化在春季萌发、秋末消衰,使夏季表层水营养盐匮乏,底层冷水团营养盐大量蓄集,因此初级生产力在5-6月和11月出现双峰特征,而近岸海水几乎全年混合均匀,初级生产力单峰出现在6-8月。河流每年为黄海输送225.4×103t无机氮和6.82×103t无机磷,使北黄海及近岸营养盐丰富,尤其朝鲜沿岸径流注入大量的营养盐,使其新生生产力较高,f比平均达55%。光合作用和呼吸作用是营养盐最大的汇和源,黄海中部沉积物-水界面交换向水体提供大量的硝酸氮,为新生产贡献56%的氮。大气沉降补充的营养盐占年初级生产所需氮、磷的6%和1.5%,为河流输入营养盐的3～5倍。

最佳管理措施评估方法研究进展

针对流域非点源污染的关键源区,进行最佳管理措施(BMPs)的配置,是非点源污染控制的有效途径。污染削减效率的准确识别对于BMPs在目标流域内的有效实施具有非常重要的意义。通过综合对比和分析实地监测、养分平衡、风险评估以及模型模拟等四类最佳管理措施评估方法的有效性、特点、适用条件及其局限性,得出以下结论:养分平衡法较为简便且易于使用,相较于其他方法,所需时间短且又可以消除评估效果的滞后效应,但对污染物削减的时间效应和传输过程影响考虑较少。风险评估和模型模拟方法可以更好地应对不同时空尺度下削减措施效率的评估,但需要大量实测数据的支持,同时模型模拟中普遍存在的时空不确定性影响很难消除。由于各种评估方法都有一定的适用条件,单一方法难以有效地完成评估目标,需要综合应用各类方法,才能最大程度地发挥这些方法的潜在功能和有效性,进而实现BMPs措施使用的成本-效益目标。

中国明对虾精养池塘氮、磷和碳收支的研究

系统化学收支的研究可以说明进入池塘生态系统各营养物质的归宿,文章应用营养盐收支法分析了池塘生态系统的物质流通。结果表明,对虾生产利用营养盐所占比例依次为氮(N),27.40%;磷(P),20.69%;碳(C),17.32%。在营养盐支出中,P的沉积作用明显,占总支出的52.04%;N在水体的悬浮和溶解较多,占61.06%;C在养殖系统的呼吸作用消耗最大,占40.86%。在封闭式池塘系统中,对虾养殖中营养盐的低利用效率为系统环境中营养盐积累的直接原因,除C通过呼吸作用得到有效释放外,大部分N、P污染元素滞留或沉积在池塘系统。