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1.
Abstract. The efficient management of clay soils depends on the rapid disposal of water following rainfall. Winter storm outfall hydrographs of under drained catchments ranging in size from 0.44 ha to 7.2 km2 are given, illustrating the drainage response of a Windsor Series soil. The response time of different sized catchments is discussed in relation to potential flood hazard arising from drainage improvements of agricultural land. Comparison is made with other soils to reveal broadly similar patterns of drainflow, with peak flow occurring typically between 1 and 4 hours after the mid-point of a storm. Despite large fluxes of water through the soil profile, the water content of the soil within the catchment of an individual tile lateral is shown to vary only by small amounts both during and after a single rainstorm and over a drainage season. 相似文献
2.
Abstract. An examination of total phosphorus (TP) concentrations from 902 lakes in England, Scotland and Northern Ireland (NI), suggest that only Scottish lakes have a high percentage (73%) of oligotrophic waters (TP<10 μg PI-1 ). The TP status of upland lakes in NI was greater than Scottish lakes particularly if lake catchments were afforested. Although lowland lakes in NI drain a predominately non-urbanized landscape, 38% of lakes below 100 m had TP concentrations > 100 μg PI-1 and only 29% <35 μg PI-1 . English lakes tended to have higher TP concentrations (70% > 101 μg PI-1 ) which may reflect P inputs from sewage treatment works (STWs) although lakes draining agricultural catchments frequently produced high TP concentrations. Between 1985 and 1995, annual point source TP inputs to Loch Leven, Scotland, declined by 8 tonnes P or 40% of the 1985 TP loadings to the Loch. As point source inputs were proportionally richer in dissolved molybdate reactive phosphorus (MRP) than diffuse inputs, the MRP loading was reduced by 46%. From 1974 to 1995, TP concentrations in Lough Neagh (NI) increased despite reduced TP inputs from STWs. Partitioning of annual TP loadings from two major inflowing rivers to Lough Neagh, showed river MRP loadings from non-point sources had been increasing at annual rates of 1.9 and 2.3 kg P km-2 . The remaining non-MRP river loadings had not been influenced by lower TP loads from STWs and showed no tendency to increase with time. Insufficient data is available from other lake systems in the British Isles to judge whether the increase in non-point source MRP loadings observed in the Lough Neagh catchment has been repeated elsewhere. 相似文献
3.
The influence of parent material and livestock intensification on plant-available phosphorus values by the Olsen method in Northern Ireland 总被引：2，自引：0，他引：2
Abstract. Leaching of phosphorus (P) from agricultural land is the major cause of eutrophication of surface waters in Northern Ireland. However, soil testing using the Olsen method has shown that while soil P in some catchment areas of the Province is low, surface waters within these catchments are, nonetheless, every bit as eutrophic as other local catchments where soil P is high. Soil P measurements on over 6000 samples from Northern Ireland soils (A horizon only) have indicated that Olsen-P values of improved grassland on most parent materials are linearly related to animal intensification. Exceptions are soils derived from peat, marl and basalt. For each of the latter soils, the measured Olsen-P was shown to be around 10 mg L–1 lower than expected for farms with similar intensification on other parent materials. In particular, the mean Olsen-P values of samples from basaltic soils under grass with total Fe above 62 g kg–1 and total Mg above 16 g kg–1 were significantly lower than those from basaltic soils with low total Fe (<37 g kg–1 ) and total Mg (<8 g kg–1 ). As a result of the depressed Olsen-P value, excessive quantities of P may be applied to these soils to maintain a recommended soil P index thereby enhancing the potential for nutrient enrichment of adjacent surface waters. In such cases, coworkers have shown that acid ammonium oxalate may be a better extractant than bicarbonate as an indicator of plant-available P. 相似文献
4.
Soil phosphorus management and water quality: a UK perspective 总被引：23，自引：0，他引：23
Abstract. An increasing proportion of P reaching surface waters appears to be derived from agricultural land; apportioning the relative contribution to particular farming systems is not straightforward. The majority of farms in the UK operate on the basis of an annual agricultural P surplus, the size of which varies across different farm types. Particularly high values (>20kg ha-1 ) are commonly associated with intensive-livestock production and the lower values (<10kg P ha-1 ) with arable farms. The geographical divide between the predominance of arable cropping in the east and livestock enterprises in the west of the UK should result in an uneven pattern to the distribution of annual P surplus. The expected cumulative effects of this surplus should be a noticeable increase in total and extractable soil P concentrations, but this is not readily apparent. While evidence from experimental plots suggests a relationship between the concentration of available soil P and that present in drainage waters, extrapolating this information so that it can be useful at the scale of a whole catchment is difficult. The loss of P from agricultural land is controlled by factors which are independent of the size of the annual P surplus. The pattern of P cycling, together with the dominant loss pathways, differ greatly between livestock and arable farming systems. Proportioning the contributions that either increased soil erosion arising from changing agricultural practices or the cumulative effect of a P surplus have had upon P loss is a necessary prerequisite to effective management. 相似文献
5.
Increased predicted losses of phosphorus to surface waters from soils with high Olsen-P concentrations 总被引：5，自引：0，他引：5
Abstract. Diffuse soluble reactive P (SRP) & total P (TP) loads from over 50 major river catchments in Northern Ireland were predicted using an export coefficient modelling approach. Phosphorus export coefficients for each CORINE land cover class, derived from satellite imagery, allowed the prediction of P loads from a breakdown of the CORINE land cover classes by catchment using a GIS. This approach was validated using observed P loads calculated from flow and concentration data. Mean measured Olsen-P concentrations in the soil A-horizon were also determined on a catchment basis. Plots of P loads to the watercourse versus Olsen-P concentrations in the soil showed a breakpoint around 22 mg Olsen- P l−1 for both SRP & TP data. Below Olsen-P concentrations of 22 mg l−1 , SRP & TP losses were essentially independent of Olsen-P at 0.28 and 0.63 kg P ha−1 yr−1 , respectively. Above Olsen-P concentrations of 22 mg l−1 , there was considerable spread in the P loss data. Nevertheless, significant upward trends in SRP and TP losses to watercourses were detected with increasing Olsen-P at a rate of approximately 0.5 and 1.0 kg P ha−1 yr−1 , for SRP and TP respectively, for each 10 mg l−1 increase in Olsen-P. 相似文献
6.
Distributed erosion and sediment yield models are being increasingly used for predicting soil erosion and sediment yields in agricultural catchments. In most applications, validation of such models has commonly been restricted to comparison of the predicted and measured sediment output from a catchment, because spatially distributed information on rates and patterns of soil redistribution within the catchment has been lacking. However, such spatially distributed data are needed for rigorous model testing, in order to validate the internal functioning of a model and its applicability at different spatial scales. The study reported in this paper uses two approaches to test the performance of the agricultural non-point source pollution (AGNPS) and areal non-point source watershed environmental response simulation (ANSWERS) erosion and sediment yield models in two small catchments in Devon, UK. These involve, firstly, comparison of observed and predicted runoff and sediment output data for individual storm events monitored at the basin outlets and, secondly, information on the spatial pattern of soil redistribution within the catchments derived from 137Cs measurements. The results obtained indicate that catchment outputs simulated by both models are reasonably consistent with the recorded values, although the AGNPS model appears to provide closer agreement between observed and predicted values. However, the spatial patterns of soil redistribution and the sediment delivery ratios predicted for the two catchments by the AGNPS and ANSWERS models differ significantly. Comparison of the catchment sediment delivery ratios and the pattern of soil redistribution in individual fields predicted by the models with equivalent information derived from 137Cs measurements indicates that the AGNPS model provides more meaningful predictions of erosion and sediment yield under UK conditions than the ANSWERS model and emphasises the importance of using information on both catchment output and sediment redistribution within the catchment for model validation. 相似文献
7.
Rong YANG Chaopu TI Feiyue LI Meihua DENG Xiaoyuan YAN 《Soil Science and Plant Nutrition》2010,56(1):86-94
To evaluate the atmospheric load of reactive gaseous nitrogen in the fast-developing Eastern China region, we compiled inventories of nitrous oxide (N2 O), nitrogen oxide (NOx ) and ammonia (NH3 ) emissions from a typical rural catchment in Jiangsu province, China, situated at the lower reach of the Yangtze River. We considered emissions from synthetic N fertilizer, human and livestock excreta, decomposition of crop residue returned to cropland and residue burning, soil background and household energy consumption. The results showed that, for the 45.5 km2 catchment, the annual reactive gaseous emission was 279 ton N, of which 7% was N2 O, 16% was NOx and 77% was NH3 . Synthetic N fertilizer application was the dominant source of N2 O and NH3 emissions and crop residue burning was the dominant source of NOx emission. Sixty-seven percent of the total reactive gaseous N was emitted from croplands, but on a per unit area basis, NOx and NH3 emissions in residential areas were higher than in croplands, probably as a result of household crop residue burning and extensive human and livestock excreta management systems. Emission per capita was estimated to be 18.2 kg N year−1 in the rural catchment, and emission per unit area was 56.9 kg N ha−1 year−1 for NH3 + NOx , which supports the observed high atmospheric N deposition in the catchment. Apparently, efficient use of N fertilizer and biological utilization of crop straw are important measures to reduce reactive gases emissions in this rural catchment. 相似文献
8.
The Phosphorus Indicators Tool: a simple model of diffuse P loss from agricultural land to water 总被引：6，自引：0，他引：6
A.L. Heathwaite A.I. Fraser P.J. Johnes M. Hutchins E. Lord D. Butterfield 《Soil Use and Management》2003,19(1):1-11
Abstract. The Phosphorus Indicators Tool provides a catchment-scale estimation of diffuse phosphorus (P) loss from agricultural land to surface waters using the most appropriate indicators of P loss. The Tool provides a framework that may be applied across the UK to estimate P loss, which is sensitive not only to land use and management but also to environmental factors such as climate, soil type and topography. The model complexity incorporated in the P Indicators Tool has been adapted to the level of detail in the available data and the need to reflect the impact of changes in agriculture. Currently, the Tool runs on an annual timestep and at a 1 km2 grid scale.
We demonstrate that the P Indicators Tool works in principle and that its modular structure provides a means of accounting for P loss from one layer to the next, and ultimately to receiving waters. Trial runs of the Tool suggest that modelled P delivery to water approximates measured water quality records. The transparency of the structure of the P Indicators Tool means that identification of poorly performing coefficients is possible, and further refinements of the Tool can be made to ensure it is better calibrated and subsequently validated against empirical data, as it becomes available. 相似文献
We demonstrate that the P Indicators Tool works in principle and that its modular structure provides a means of accounting for P loss from one layer to the next, and ultimately to receiving waters. Trial runs of the Tool suggest that modelled P delivery to water approximates measured water quality records. The transparency of the structure of the P Indicators Tool means that identification of poorly performing coefficients is possible, and further refinements of the Tool can be made to ensure it is better calibrated and subsequently validated against empirical data, as it becomes available. 相似文献
9.
Meeting the UK's climate change commitments: options for carbon mitigation on agricultural land 总被引：1，自引：0，他引：1
Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO2 emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.
We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr−1 ) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no-till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land-use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr−1 (equivalent to about 6.6% of 1990 UK CO2 -carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.
The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously. 相似文献
We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr
The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously. 相似文献
10.
Abstract. A model has been developed based on multiple regression which explains 95% of the variation in nitrate loading of the major rivers in the 4453 km2 Lough Neagh catchment for the years 1971–1987. The model relates loading of nitrate in the hydrological year to fertilizer usage, previous summer rainfall, summer temperature of the current year and December-May flow. It indicates that there is an increase in nitrate loading associated with fertilizer usage, and that the equivalent of 13% of nitrogen fertilizer that is lost as leachate comprises 50% of the river loadings. 相似文献
11.
Abstract. Organic agriculture (OA) aims to identify a production regime that causes less environmental problems than conventional agriculture (CA). We examined whether the two systems differ in their susceptibility to soil erosion by water. To account for the large heterogeneity within the rotations practised on different farms, we chose a statistical evaluation which modelled erosion using the USLE method from the cropping statistics for 2056 districts in Bavaria (70 547 km2 ; 29.8% arable). Physical conditions of erosion were determined in a rectangular grid yielding 13 125 grid-cells of c. 5 km2 each. For validation, erosion was measured in 10 sub-watersheds on two neighbouring OA and CA farms over 8 years (287 erosive events). On average, about 15% less erosion on arable land was predicted for OA than for CA due to the larger area of leys, although OA occupies areas that are susceptible to erosion more often than CA. The same conclusions could be drawn from the validation data. These data also demonstrated that erosion could be reduced considerably below 1 t ha−1 yr−1 with best management practices under both farming systems. In contrast, at the countrywide scale, cropping did not change adequately with site conditions favouring erosion. The need for erosion control seems not to influence crop rotation decisions on erosion-prone sites. 相似文献
12.
Simple phosphorus saturation index to estimate risk of dissolved P in runoff from arable soils 总被引：1，自引：0，他引：1
Abstract. There is increasing evidence that phosphorus has been accumulating in the surface horizons of agricultural soils to the extent that some soils represent a potential diffuse source of pollution to surface waters. The relationships between equilibrium phosphorus concentration at zero sorption (EPC 0 ) of soil and a number of soil physicochemical variables were investigated in the surface layers of arable and grassland agricultural soils sampled from the Thame catchment, England. Soil EPC0 could be predicted from an equation including soil test (Olsen) P, soil phosphate sorption index (PSI) and organic matter content (OM) (R2 =0.88; P <0.001) across a range of soil types and land use. The simple index Olsen P/PSI was found to be a good predictor of EPC0 (R2 =0.77; P <0.001) and readily desorbable (0.02 m KCl extractable) P (R2 =0.73; P <0.001) across a range of soil types under arable having soil organic matter contents of <10%. 相似文献
13.
Abstract. This study was undertaken to test the hypothesis that an improved system of catchment management in combination with appropriate cropping practices can sustain increased crop production and improve soil quality of Vertisols, compared with prevailing traditional farming practices. Initiated in 1976, the improved system consisted of integrated land management to conserve soil and water, with excess rainwater being removed in a controlled manner. This was combined with improved crop rotation (legume based) and integrated nutrient management. In the traditional system, sorghum or chickpea was grown in the post-rainy season with organic fertilizers, and in the rainy season the field was maintained as a cultivated fallow. The average grain yield of the improved system over 24 years was 4.7 t ha−1 yr−1 , nearly a five-fold increase over the traditional system (about 1 t ha−1 yr−1 ). There was also evidence of increased organic C, total N and P, available N, P and K, microbial biomass C and N in the soil of the improved system. A positive relationship between soil available P and soil organic C suggested that application of P to Vertisols increased carbon sequestration by 7.4 t C ha−1 and, in turn, the productivity of the legume-based system, thus ultimately enhancing soil quality. 相似文献
14.
Abstract. An area of about 24 km2 in arable East Lothian, Scotland, was examined for soil erosion by water following a severe rainstorm in October 1990. Significant erosion was found in only 10 fields out of 26.5 in an area where topography, soils and cropping suggest a high erosion risk. Doubt is cast on some assessments of the widespread risk of significant soil erosion by water in arable areas of the UK. 相似文献
15.
Z. L. Frogbrook J. Bell R. I. Bradley C. Evans R. M. Lark B. Reynolds P. Smith & W. Towers 《Soil Use and Management》2009,25(3):320-332
Intensive field surveys were undertaken in two upland catchments in the UK, Plynlimon in mid-Wales and Glensaugh in North East Scotland. The survey was to examine the spatial variation across the area and to assess the accuracy of the database underpinning the soil carbon map for the UK. In each area three 1-km2 squares were sampled on a 200-m grid, with samples taken from both the organic and mineral horizons. Carbon stock was estimated, from the sample data, for each 1-km2 square and compared with values from the UK database for that square. The results showed large differences between some squares, particularly for Plynlimon. In this area, the overall discrepancy between field and database values was 45%, compared with 8% for Glensaugh. Various sources of uncertainty were examined, including bulk density, organic horizon depth, and the proportion of different soil types within a square. The value for bulk density, assumed to determine carbon stock, had a significant effect on the estimates. In both catchments the organic layer showed a gradual decrease in bulk density with depth, resulting in a large proportion of the carbon being stored in the top part of the profile. The soil types, mapped during the survey, also showed large differences from those previously identified for each 1-km2 square. This would have a considerable effect on the estimates of carbon stock within the UK database. It highlights that caution needs to be used when interpreting the UK soil map at this spatial scale. 相似文献
16.
Agricultural nitrogen balance and water quality in the UK 总被引：2，自引：0，他引：2
Abstract. Nutrient balance calculations have been advocated as indicators of the risk of nitrate loss from agricultural land. To explore this concept, a spatially distributed UK agricultural nitrogen balance was derived using annually updated statistics. The mean UK N surplus for 1995 was 115 kg N ha–1 , made up of 51 kg ha–1 for arable land, 140 kg ha–1 for agricultural grassland (excluding rough grazing) and an additional 14 kg N ha–1 for agricultural land from pig and poultry units. Nitrogen surpluses were greater in lowland grassland (mainly in western, wetter areas) than in arable areas. However nitrate concentrations in rivers were generally greater in arable areas. The relationship between N balance and nitrate leaching was very different for grassland and arable systems, and was also sensitive to climate, level of inputs and management practices. Nitrogen surplus was therefore weakly or even negatively correlated with river nitrate concentrations or loads. A positive correlation was found only where the comparison was restricted to grassland-dominated catchments. Nitrogen surplus calculations identified areas of very high livestock densities, which would be associated with increased risk of pollution. However their use in isolation as indicators of N leaching, or of progress towards mitigation, could be misleading especially if comparing areas differing in land use, climate or soil type. 相似文献
17.
P. S. Hooda M. Moynagh I. F. Svoboda M. Thurlow M. Stewart M. Thomson H. A. Anderson 《Soil Use and Management》1997,13(4):196-204
Abstract. Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland. The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stocked/arable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.
Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO4 -P/l as molybdate-reactive phosphate–MRP) compared with the northeast (0.012-0.025 mg PO4 -P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn. 相似文献
Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO
18.
Abstract. This paper describes the results of laboratory-based research which investigated the losses of the herbicide, isoproturon, and a non-adsorbing solute, bromide, from topsoil aggregates under high (7 mm h−1 and low 2.7 mm h−1 ) intensity simulated rainfall. The structures of the micro- and macro-aggregates from a clay soil of the Denchworth Series (from Wytham, Oxfordshire, UK) were observed using a scanning electron microscope, and the slaking of the topsoil aggregates was also investigated in order to provide a context for interpreting the experimental results. The topsoil at Wytham was found to have a bimodal structure with small microaggregates of 0.71 to 1 mm diameter clustered together to form larger macroaggregates of up to several centimetres diameter. Selected aggregates were air dried and then repacked in Buchner funnels to several centimetres depth in order to remove variability in the experimental results due to the effects of surface microrelief. Under saturated surface conditions high intensity simulated rainfall was less efficient at removing both non-adsorbing and adsorbing solutes from the repacked topsoil aggregates than low intensity rainfall. The observed decrease in the concentration of isoproturon and bromide in the leachate with time could be explained by a transport non-equilibrium effect. 相似文献
19.
Abstract. The incidence of soil water erosion was monitored in 12 erosion-susceptible arable catchments ( c . 80 fields) in England and Wales between 1990 and 1994. Factors associated with the initiation of erosion were recorded, and the extent of rills and gullies measured. Approximately 80% of the erosion events were on land cropped to winter cereals. In 30% of cases, the initiation of erosion was linked to valley floor features, which concentrated runoff. Poor crop cover, wheelings and tramlines were also assessed as contributory factors in 22%, 19% and 14% of cases, respectively. In c . 95% of cases rainfall events causing erosion were ≥10 mm day−1 and c . 80% were >15 mm day−1 . Erosion was also associated with maximum rainfall intensities of >4 mm h−1 for c . 90% of cases and >10 mm h−1 for c . 20%. Mean net soil erosion rates were approximately 4 t ha−1 per annum (median value 0.41 t ha−1 per annum) and associated mean P losses 3.4 kg ha−1 . 相似文献