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1.
Abstract. Experiments were started in 1967 to investigate the effects of soil mixing on fen peat soil. Peaty topsoil was mixed with mineral subsoil to a maximum depth of 80 cm at two sites, one with a clay subsoil, the other sand. Mixing was done on a commercial scale with a range of implements. After initial increases, yields of arable crops on both mixed soils were subsequently similar to those on unmixed soil. Residual herbicide activity was enhanced on mixed soils, and evidence of peat conservation was obtained at one site. The practice has not been taken up commercially because of the high capital cost of mixing and lack of serious problems which had been predicted following peat wastage.  相似文献   

2.
Bromide transport at two tile- drained field sites Within comparative studies on solute movement in tile drained agricultural fields in Schleswig-Holstein a bromide field test was conducted at two field sites. The soil of site ‘Bokhorst’ shows both spatial and profile heterogeneity with significant clay and silt contents (loam) whereas site ‘Hohn’ had a homogeneous particle size distribution within the profile with sand being the dominating particle fraction (sand) but with neglible spatial variability. Rainfall amount, drain discharge and bromide concentrations in drain outflow were monitored over a 6 months period. A rapid response of drain discharge on rain events was observed for the loamy site but not for the sand. The simple water balance yielded + 8.7 mm of drain discharge for site Bokhorst (loam) and ?43 mm for the sandy site Hohn (sand). Largest bromide concentrations were detected shortly after chemical application at the loamy site. The bromide loss curve was characterized by simultaneous in- and decrease of flow rate and bromide concentrations. This solute behaviour was named ‘event-dependent’. Bromide occurred in drain outflow at the sandy site not before 30 mm discharge and maximum concentrations were observed at the end of the monitoring period. Mass balance calculations revealed that 70.5% (loam) and 33% (sand) of the applied solute mass were transported from the fields via the tile drains. A two dimensional, advection dispersion equation based simulation model was applied to predict solute behaviour at site Bokhorst. Computed bromide concentrations were not in line with the observed preferential breakthrough curve. Consequences of preferential transport conditions in tile-drained field soils on surface water quality are briefly discussed, especially concerning the displacement of plantprotective agents and methodical difficulties.  相似文献   

3.
Flooding events often eradicate all of the individuals of the earthworm species Lumbricus rubellus living in river floodplains, although earthworm cocoons usually survive immersion, permitting populations to recover after the flood waters recede. Yet, if the area is flooded again before earthworms hatching from cocoons or migrating from adjacent areas reach reproductive maturity, it is unlikely that their populations will recover. The objective of this study is to determine the importance of the length of the dry period for population recovery in L. rubellus. Earthworms were collected at three floodplain sites along the Rhine River that were frequently, moderately or seldom flooded. Reproductively mature L. rubellus from the frequent flooded site were half the weight and probably younger than those from the other sites. A mechanistic population model was used to estimate the time for earthworm development from hatching to reproductive maturity, and to calculate the probability of population recovery after flooding. The model results show that the probability of extinction increases when the dry period is not long enough for individuals to reach reproductive maturity. When this condition is met population extinction is virtually absent resulting from the high lifetime reproductive output of L. rubellus. Parameterization of the model with site-specific data indicate that population survival on the site with the shortest dry period drastically decreases if worms mature at the weight measured at the other sites. The results therefore strongly suggest that the dry period is critical for population recovery in river floodplains and that earthworm populations have adapted to local (site-specific) conditions.  相似文献   

4.
Site specific variables and anthropogenic factors influence composition of soil organic matter (SOM). We evaluated quantity and quality of SOM under different fertilization regimes and site conditions. The study combines data based on repeated measurements obtained from six long-term field experiments, which have been established between 1955 and 1983 at ten locations, resulting in thirteen site and experiment combinations. The experimental sites cover a wide spectrum of pedological and climatic conditions of the Czech Republic. Four basic fertilization regimes were selected: unfertilized plots, mineral-only fertilized plots, plots with application of farmyard manure, and both organic and mineral fertilized plots. The study employs compositional data analysis, principal component analysis, and mixed effect linear models for statistical inference. Under combined organic and mineral fertilization, total soil organic C (SOC) increased by 1?3 g kg?1. Evidence of possible priming effect was obtained for mineral-only fertilization. Local site conditions were the dominant factor shaping SOM properties. The positive relationship between proportion of clay in soil and decomposition index (DI) was confirmed. In the absence of fertilization, DI was eleven times higher in clay-rich than in clay-poor soil. This effect was moderated by fertilization, decreasing to a seven-fold difference under the full fertilization regime.  相似文献   

5.
Precipitation that falls on compost sites picks up organic material from the windrows and the composting pad. The resulting runoff can contain high levels of nutrients, suspended solids, and organic matter, making it unsuitable for direct release into a receiving water body. Many jurisdictions require that the runoff from these sites be collected in a detention pond. Unfortunately, some of the recommended or required procedures for quantifying the volume of runoff from these sites are based on archaic or inappropriate hydrologic models. The development of better hydrologic models for open composting operations has been hampered by a lack of basic information regarding rainfall/runoff relationships at windrow composting sites. In this paper, a standard hydrologic model — the unit hydrograph method – is used to model the hydrology of a small, paved composting site. The model results compare well with field data collected at the site over a six month period. The volume of runoff predicted by the model was within 5% of the measured runoff volume for each of seventeen runoff events observed at the site over the study period. The results suggest that other industry standard hydrologic models can be adapted for use at open composting sites to account for the presence of large quantities of organic material on the site.  相似文献   

6.
真菌群落沿气候梯度与植物凋落物分解之间的关系研究   总被引：1，自引：0，他引：1  
The decomposition of plant litter is a major process of equivalent status to primary production in ecosystem functioning. The spatiotemporal changes in the composition and dynamics of litter fungal community along a climate gradient ranging from arid desert to humid-Mediterranean regions in Israel was examined using wheat straw litter bags placed at four selected sites along the climate gradient, arid, semi-arid, Mediterranean, and humid-Mediterranean sites. Litter samples were collected over a two-year decomposition period to evaluate litter weight loss, moisture, C：N ratio, fungal composition, and isolate density. The litter decomposition rate was found to be the highest during the first year of the study at the Mediterranean and arid sites. Although the Shannon-Wiener index values of the fungal communities in the litter samples were the highest at the humid-Mediterranean site, the number of fungal species was not significantly different between the four study sites. Different fungal groups were found to be related to different study sites： Basidiomycota, Mucoromycotina, and teleomorphic Ascomycota were associated with the humid-Mediterranean site, while Coelomycetes were mostly affected by the arid site. Our results indicate that climate factors play an important role in determining the structure of saprotrophic fungal communities in the decomposing litter and in mediating plant litter decomposition processes.  相似文献   

7.
We tested the hypothesis that there would be measurable losses of phosphorus (P) from surficial sediments of Upper Klamath Lake (UKL), Oregon, if sediments were a source of P during an algal bloom. We compared concentrations of total and forms of P at various depths in cores collected before and after the onset of a large Aphanizomenon flos-aquae bloom. Concentrations of inorganic P were determined in extraction solutions of MgCl2 (1 M, pH 8), citrate-dithionite-bicarbonate, and 1 M HCl. Sediments below 2 cm were dominated by residual P which is defined as total P minus inorganic P. During the study period, data from the top 2-cm of sediment indicated (a) significant decrease in total P concentration, primarily associated with iron oxyhydroxides at one site, and (b) significant increase in total P concentration associated with residual P at a second site. Data from two other sites indicated no net changes in concentrations of total P.  相似文献   

8.
夏季不同饮水器和水压对保育猪水利用情况的影响   总被引：2，自引：1，他引：1  
养猪生产中猪饮水器用水中漏水将增加污水产生量,环境温度和供水水压及饮水器类型均会对饮水器总用水量产生重要影响.该文选择夏季不降温的保育猪舍,通过试验研究了不同饮水器和供水压力对保育猪用水量和浪费水量的影响.用水量和浪费水量每分记录1次.试验的第一个阶段,用10头/圈的保育猪比较了在水压为0.10,0.15和0.20MPa时杯式饮水器和swing饮水器对用水量和浪费水量的影响;第二个阶段,用5头/圈的保育猪比较了在水压为0.10MPa时带片swing饮水器和标准swing饮水器对用水量和浪费水量的影响.结果表明:在水压为0.1,0.15和0.20MPa时,杯式饮水器每头猪的用水总量分别为16.2±3.0,30.3±8.1和38.3±4.8L/d,swing饮水器的用水总量分别为5.7±1.0,8.7±1.9和10.3±0.4L/d.在0.1,0.15和0.20MPa下,杯式饮水器浪费水量/用水总量预测值分别为83.3%,85.1%和85.4%;swing饮水器浪费水量/用水总量分别为54.4%,48.3%和45.6%.带片swing饮水器每头猪用水总量(11.3±1.7L/d)没有显著高于标准swing饮水器的用水量(9.4±1.0L/d)(P>0.05).但是带片swing饮水器的浪费水量/用水量(60.2%)显著高于标准swing饮水器的浪费水量/用水量(46%)(P<0.05).因此,为了减少保育猪用水总量和浪费水量,应控制水压或者调节饮水器水流量至适宜值.在夏季不降温猪舍,与swing饮水器相比,杯式饮水器将增加用水总量和浪费水量.相对于标准swing饮水器,带片swing饮水器的使用没有减少水的浪费.  相似文献   

9.
Abstract. Two hill pastures in north Dyfed, Wales, were each treated at reseeding in 1971 with 2.25, 4.5 and 9.0 kg ha−1 cobalt sulphate. Herbage samples for analysis of Co content were taken in summer at each site from 1971 to 1976 and also at site 1 from 1977 to 1983. Acetic acid extractable Co was measured in soil samples taken each winter for the same period at both sites. At site 1, on a peat, the treatments continued to give worthwhile increases in herbage and soil Co after 13 years. At site 2, on a mineral soil, the residual effects were small and lasted no more than four years. It is suggested that me lower response and residual value at site 2 is due to higher levels of exchangeable and easily reducible manganese.  相似文献   

10.
Abstract

Ground water wells from unfertilized Florida rangelands were sampled to monitor water quality parameters. Ground water was collected (1990–92) monthly from three range sites (south Florida flatwoods, slough, and freshwater pond) at the Southwest Florida Research and Education Center near lmmokalee, Florida. Water samples were analyzed for pH, electrical conductivity, total phosphorus (P), potassium (K), and ammonium‐nitrogen (NH4‐N); and water table depth was monitored monthly. Levels of nutrients were highly variable during the sampling period. Levels of P at all three sites exceeded the South Florida Water Management District's (SFWMD) maximum allowed level (0.18 mg P/L) in surface water runoff from rangeland. Time series models were useful for predicting (p<0.15) future events for all nutrients and water table depth. Variation in water quality, related to its N, P, and K content, was minimized by excavating the ground water wells three times before sampling. Water samples continue to be collected from each range site to develop a longterm water quality database from unfertilized rangeland.  相似文献   

11.
Abstract

Temporal changes in the scores of selected soil fertility indices were studied over six years in three different cases of organic crop rotation located in southern, eastern and central Norway. The cropping history and the initial scores of fertility indices prior to conversion to organic cropping differed between the sites. Crop yields, regarded as an overall, integrating fertility indicator, were in all rotations highly variable with few consistent temporal trends following the first year after conversion. On the site in eastern Norway, where conversion followed several years of all-arable crop rotations, earthworm number and biomass and soil physical properties improved, whereas the system was apparently degrading with regard to P and K trade balances and contents in soil. On the other two sites, the picture was less clear. On the southern site, which had a relatively fertile soil before conversion, the contents of soil organic matter and K decreased during the six-year period, but the scores of other fertility indices showed no trends. On the site in central Norway, there were positive trends for earthworm-related indices such as worm biomass and tubular biopores, and negative trends for soil porosity. The results, especially those from the eastern site, illustrate the general difficulty in drawing conclusions about overall fertility or sustainability when partial indicators show divergent trends. Consequently, the study gave no unambiguous support to the initial working hypothesis that organic farming increases inherent overall soil fertility, but rather showed that the effect varied among indicators and depended on status of the cases at conversion. It is concluded that indicators are probably better used as tools to learn about and improve system components than as absolute measures of sustainability.  相似文献   

12.
Aliphatic and aromatic hydrocarbons, fatty acids and heavy metals (Pb, Cu, Ni, Zn, Fe and Cd) were analyzed in bulk deposition samples at two locations within the metropolitan area of Caracas, Venezuela. One of the sampling sites was located in the center (urban site, 1), while the other was in the outkirts of the city (rural site, 4). In general, a higher flux was observed for the deposition of pollutants at site 1 than at site 4. These fluxes showed relatively large short-term variations, while the long-term integrated deposition was found to be relatively constant throughout the sampling period. Wet deposition did not affect the flux of most of the pollutants studied, with the exception of Pb and the fatty acids of an anthropogenic origin.  相似文献   

13.
Effect of cropping systems on phosphatases in soils   总被引：2，自引：0，他引：2  
Phosphatases are widely distributed in nature and play a major role in phosphorus nutrition of plants. The effects of crop rotations and nitrogen fertilization on the activities of phosphatases (acid phosphatase, alkaline phosphatase, and phosphodiesterase) were studied in soils from two long‐term cropping systems at the Northeast Research Center (NERC) in Nashua and the Clarion Webster Research Center (CWRC) in Kanawha, Iowa, USA. Surface soils (0—15 cm) were taken in 1996 and 1997 from replicated field plots in corn, soybeans, oats, or meadow (alfalfa) that received 0 or 180 kg N ha—1 before corn. Because of differences in organic C contents among soils of the two sites, the soils from the CWRC sites contained greater enzyme activity values than those from the NERC site. Plots under oats or meadow showed the greatest activity values, whereas those under continuous corn at the CWRC site and soybean at the NERC site showed the least activities. Analysis of variance indicated that the activities of the phosphatases were significantly affected by crop rotation (P < 0.001) in both years at the NERC site but not at the CWRC site. Nitrogen fertilization affected the activity of acid phosphatase in soils from the CWRC site in both years and alkaline phosphatase only in 1997; but it did not affect the activities of the phosphatases in the soils from the NERC site. With the exception of alkaline phosphatase (CWRC) and phosphodiesterase (NERC) in soils sampled in 1997, activities of alkaline phosphatase and phosphodiesterase were significantly correlated with microbial biomass C (C mic) in soils from both sites and years, with r values ranging from 0.366* to 0.599***. Cropping systems and N fertilization affected the specific activities of phosphomonoesterases, especially acid phosphatase, but not of phosphodiesterase. Regression analysis showed that activities of phosphatases were significantly correlated with organic C contents of soils from the NERC site but not from the CWRC site.  相似文献   

14.
Bulk precipitation samples were collected from ten sites in south-central Maine during the period 18 June to 30 September, 1974. Data from the chemical analyses of the precipitation were used to determine regional deposition patterns of the ionic constituents. Acidic pH values ranging from 3.8 to 5.0 are characteristic of the region, but relatively alkaline pH values of 5.5 to 7.0 were observed in the precipitation from one collection site. Systematic increases in sulphate and Na deposition in the samples from this site suggest a local source. The observations of the bulk precipitation analysis lead to a study of the chemical composition of precipitation near a kraft paper mill. Samples were collected during single precipitation events. The results indicate that this source can affect background levels of composition up to a distance of at least 20 km and that considerable care must be taken in the selection of sites for sampling background precipitation.  相似文献   

15.
未来气候变化对农牧交错带不同灌溉水平马铃薯产量和水分利用的影响鲜有研究。该研究基于农牧交错带张北和武川站不同灌溉条件下大田试验数据评估了APSIM-Potato模型的适应性;基于33个全球气候模式(global climate model,GCM)通过统计降尺度方法获得的未来2个气候情景(RCP4.5和RCP8.5)逐日气候数据驱动APSIM-Potato模型,模拟未来气候变化对不同灌溉水平(灌1水、灌2水、灌3水和灌4水)马铃薯产量和水分利用的影响。结果表明:APSIM-Potato模型能够较好地模拟2个站点马铃薯产量和土壤水分动态。2个站点实测产量和模拟产量的相对误差均小于22.6%,实测土壤水分和模拟土壤水分相对均方根误差均小于18.1%。基于33个GCM模拟结果,2030 s、2060 s和2090 s马铃薯生育期温度、CO2浓度、总降水量和总辐射量相比于基准期(1981-2010)均呈增加趋势。相比于基准期灌1水、灌2水、灌3水和灌4水马铃薯产量,张北站和武川站在RCP4.5情景下均有提升,张北站为4.1%~36.2%,武川站为2.5%~13.6%。RCP8.5情景下,2个站点分别提升3.1%~36.8%和3.1%~38.5%。且2个气候情景下均是灌1水情景下马铃薯产量提升最高。2个气候情景下,马铃薯水分利用效率在2030 s-2090 s均呈增加趋势。研究结果表明未来气候变化对农牧交错带地区马铃薯产量和水分利用效率具有积极影响,未来气候情景下该地区更适宜灌溉马铃薯的生产。  相似文献   

16.
In a field study, conducted on 10 conventionally managed field sites in Germany, the effects of high axle loads (15–25 Mg) on soil physical properties were investigated. Soil texture classes ranged from loamy sand to silty clay loam. All sites were annually ploughed, and one site was additionally subsoiled to 40 cm depth. In the context of common field operations wheeling was performed either by a sugar beet harvester (45 Mg total mass, 113 kPa average ground contact pressure) or a slurry spreader (30 Mg total mass, 77 kPa average ground contact pressure). Soil moisture conditions varied from 3.2 to 32 kPa water tension during this pass. Penetration resistance was measured before the pass. Soil cores were collected in a grid scheme at each site before and after the machine passed. Bulk density, aggregate density, air-filled porosity and air permeability at seven distinct soil water tensions ranging from 0.1 to 32 kPa were determined in these cores taken from three layers (topsoil, plough pan and subsoil).At most sites, a pass by the sugar beet harvester or slurry spreader strongly affected topsoil properties. Bulk density and aggregate density increased while air-filled porosity and air permeability decreased. The plough pan was already severely compacted before wheeling: therefore changes were small. The subsoil showed no changes or only minor signs of compaction. Only at one site, which was subsoiled the year before, significant signs of compaction (i.e. changes in bulk density, air-filled porosity and air permeability) were detected in subsoil layers.The results show that using present-day heavy agricultural equipment does not necessarily lead to severe subsoil compaction in soils where a compacted plough pan already exists. However, fields which were subsoiled leading to an unstable soil structure are in serious danger of becoming severely compacted.  相似文献   

17.
Wet and dry deposition inputs and streamflow output of Cd, Mn, Pb, Zn, and Al were measured intermittently at four deciduous forested watersheds in the southeastern United States between 1976 and 1982. Atmospheric inputs to each site were similar, varying by factors of 1.1 to 2.2 for the different metals. Metal levels in precipitation indicate that these sites are representative of rural, continental areas. Metals in rain exhibit significant temporal and spatial trends, with concentrations generally higher during summer than winter at all sites and generally lowest at the more remote site. The concentrations of Cd and Pb in both wet and dry deposition decreased between the period 1976 to 1977 and 1981 to 1982. Ion ratios and enrichment factors suggest that Mn is largely soil derived in atmospheric samples while Cd, Pb, and Zn are enriched over typical soil levels. Factor analysis indicates that soil components influence both Al and Mn while fine aerosol components influence Cd in wet and dry deposition. Both components influence the behavior of Pb. Dry deposition dominated the input of Mn and Al to each site, while wet deposition was the major input process for the other metals (54 to 85% of total). On an annual basis, deposited Cd, Pb, and Zn are strongly retained in each watershed: 2% of the Pb, 8 to 29% of the Cd, and 8 to 34% of the Zn inputs were transported in stream flow. Deposited Mn and Al are retained to a lesser degree and show a net loss from two sites. Metal export is controlled by stream pH, organic carbon, bedrock geology, and hydrologic characteristics of each site.  相似文献   

18.
近150年来长江入海流量变化的趋势、阶段与多尺度周期   总被引：1，自引：0，他引：1  
[目的]分析近150a来长江入海流量变化的长期趋势、阶段性、突变性以及多尺度周期变化过程,为揭示长江入海流量的长期变化特征提供理论支撑。[方法]基于长江汉口站长时间实测水文数据,利用现代汉口站和大通站流量一元回归模型,恢复以长江大通站为代表的1865—2014年长江入海流量序列。综合利用多种方法开展多尺度分析。[结果]长江近150a入海流量序列表明,平均值为29 432m~3/s,变异系数为14.72%。趋势分析表明,近150a来长江入海流量呈现下降趋势,变化速率为-23.7m~3/(s·a)(p0.01)。阶段性分析表明,长江入海流量变化具有一定的波动性特征,大体上以1955年为分界点,在1865—1955年为流量上升阶段,1955—2014年为流量下降阶段。突变性分析表明,长江入海流量在1940s发生了突变,由丰水期转变为枯水期。多尺度周期性分析表明,长江入海流量变化过程表现出明显的非线性和非平稳性,具有150和60a的长期趋势,以及34,22,3~7a的中高频振荡周期,其中22a周期最为明显,可以通过99%置信度检验。[结论]近150a来长江入海流量总体上呈下降趋势;其中自1955年以来长江入海流量处于一个显著的下降期;长江流域降水量变化是影响长江入海径流变化的重要因素。  相似文献   

19.
内蒙古草原地处季节性冻土区,与放牧强度相关,土壤冻融过程对该地生态和水文过程有着显著影响,但相关研究相对欠缺。该文重点研究了内蒙古锡林郭勒草原3种放牧条件下UG79(1979年以来禁牧)、UG99(1999年以来禁牧)、HG(1979年以来持续放牧)季节性冻融期的土壤水热动态,以期准确理解放牧这一当地主要土地利用模式对土壤生态水文过程的影响。结果表明:与地上覆盖度相关,不同放牧条件下地表积雪厚度有明显差异,其中HG处理积雪厚度远小于其他处理,其土壤温度变化也最为剧烈。与不同处理土壤冻结速率相关,土壤冻结时HG,UG79和UG99的"聚墒区"分别为20—30cm,10—20cm和10—30cm,其中UG99"聚墒区"分布范围最广,且集中在牧草根系发达区域,对来年牧草生长提供了更好的水分条件。换言之,由于冻后聚墒效应,土壤消融期水分含量在土壤表层高于冻融前,其中UG99处理最大,达到了0.19m~3/m~3。该研究结果为内蒙古草原季节性冻土区控制放牧及合理的禁牧措施提供理论依据。  相似文献   

20.
云南烤烟5项化学成分含量与其环境生态要素的关系   总被引：25，自引：5，他引：25  
基于云南565个植烟点的土壤、烟叶取样测试分析数据和由实测气象站网推算的气象数据，应用分类分级方差对比、相关分析和等级化平滑过滤干扰的要素响应分析三种方法，研究揭示了品种、土壤、气象三因素综合影响下各主要要素对烤烟化学成分含量影响的相对大小；基本明确了云南烟叶中总糖、还原糖、烟碱、总氮和蛋白质含量与土壤基本要素、各时段基本气象要素的关系。光、温、水气象条件是影响云南烤烟5项化学成分的主要生态要素；在光、温、水总量基本满足烤烟经济种植需求的前提下，云南烟区光、温、水三要素在大田期间的时段分布和匹配比其大田期总量对烟叶5项成分含量的影响大。云南烤烟大田前期（4—5月）少雨多光照、湿度小、气温较高和日较差大的天气气候，既提高烟叶含糖量又降低烟碱、总氮和蛋白质含量；其大田中后期（尤其7—8月）多雨寡照、湿度大、气温偏低和日较差小的气象条件，有相反的影响效应。大田期各月气温与烟叶含糖量呈负相关，对烟碱含量影响不显著；7—8月气温高可提高烟叶总氮和蛋白质含量。土壤因素对烟叶5项成分的影响总体上小于气象因素；烤烟4个优良品种间的烟叶5项成分含量差异不显著。  相似文献   

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