bluuebunny/crossref_metadata_2025 huggingface dataset:
Mobility of metals in Egyptian desert soils subject to inundation by Lake Nasser
Authors: Moalla S.N. , Pulford I.D.
Published: February 2007

Abstract. Extraction and adsorption techniques were used to study the behaviour of Al, Fe, Mn, Co, Ni, Cu and Zn in soils from around Lake Nasser in the Eastern Desert of Egypt, to assess the potential of such areas for agricultural development and the risks of pollution of the lake. Soil metal contents were very variable, either because of particle size sorting by flowing water or through changes in redox resulting from flooding by lake water. Metal availability was low. Extraction using EDTA and oxalate suggested that mobility of copper was controlled by carbonate, whereas Co, Ni and Zn were controlled by Fe and Mn oxides. Adsorption studies confirmed the strong ability of these soils to remove Cu and Zn from solution, and suggested that Cu and Zn concentrations in solution were controlled by carbonate. Some trace metal fertilizers will probably be required for certain crops, but pollution of the lake by leaching of metals from soil is unlikely. The main process by which metals could be lost from the soil to lake water is a lowering of soil redox potential as a result of flooding by lake water.
The effect of humic acids on the availability of phosphorus fertilizers in alkaline soils
Authors: Wang X.J. , Wang Z.Q. , Li S.G.
Published: February 2007

Abstract.The effect of humic acids on transformation of phosphorus fertilizer was studied in an alkaline soil. Soil P was fractionated following 4 and 15 days incubation after humic acids were applied with phosphorus fertilizer to the soil. The availability of phosphate in the soil and total phosphorus in plants were determined at earing stage and at maturity in a pot experiment, and wheat yield was examined in a field trial. Addition of humic acids to soil with P fertilizer significantly increased the amount of water soluble phosphate, strongly retarded the formation of occluded phosphate and increased P uptake and yield by 25%.
Rock fragments I. Their effect on runoff, erosion and soil properties under field conditions
Authors: Moustakas N.C. , Kosmas C.S. , Danalatos N.G. , Yassoglou N.
Published: February 2007

Abstract.The effects of different sizes, amounts, and positions of rock fragments on soil properties and erosion were studied in experimental plots (10 treatments including bare soils and soils under natural vegetation, with 3 replicates each) installed on a hillslope.

Over five events, the largest amounts of runoff were from bare soils containing abundant rock fragments, either partially embedded on the surface or incorporated in the upper part of the soil. Stoneless soils gave smaller amounts, and the smallest runoffs were measured on soils under natural vegetation. Generally, large rock fragments (cobbles) caused greater runoff than smaller fragments (coarse gravel). However, soils with appreciable amounts of coarse gravel on the surface generated considerable runoff under rainfalls of low intensity and long duration, but smaller amounts at greater rainfall intensities.

Sediment loss was greater from soils with cobbles than from soils containing coarse gravel; vegetation greatly decreased sediment loss from both.

In a 12‐month period, the organic matter content of the soils decreased by 15.5 to 23.0%, decreasing soil aggregate stability. The organic matter content was greater in the collected sediments than in the soil.
Vegetation and soil acidity of a mangrove swamp in southeastern Nigeria
Authors: Ukpong L.E.
Published: February 2007

Abstract.The relationships between vegetation and acid properties of soils from a mangrove swamp in southeastern Nigeria were examined. Field moist soils were moderately acidic with pH ranging from 5.3 to 6.8. Air dry pH ranged from 2.9 to 4.9 indicating strong acidity; the values increased with profile depth and were related to decreasing fibrous root content. Less acidic conditions (air dry pH 4.3–4.9) were associated with the less fibrous soils underAvicennia africanaandPandanus candelabrum; more acidic conditions (air dry pH 2.9–3.8) occurred in the more fibrousRhizophoraspp. andNypa fruticanssoils. Species occurrences and levels of aluminium and sulphate in the profiles were related, suggesting that hydrogen ions, aluminium and sulphate were the main contributors to exchangeable acidity. Unless crops are known to tolerate very acidic conditions, the fibrousRhizophoraandNypasoils should not be drained for cultivation.
The influence of soil management on drainage hydrographs
Authors: Dougherty E. , Leeds‐Harrison P.B. , Youngs E.G. , Chamen W.C.T.
Published: February 2007

Abstract. Drainage hydrographs from mole‐drained plots having different tillage treatments (tractor tined, gantry tined, tractor ploughed and gantry ploughed) were measured for different rain events over a growing season. In the autumn just after tillage, a large rainfall produced peaky drain flows on the tined plots but a rather flat response from the ploughed plots. In the winter, the drain response to a small rain event showed less differences in peak flows between the treatments. The recession time constant of the hydrographs was used as an index of the structural macropore development in the soil above the water table. Hydrographs from the gantry plots recessed more quickly than those on the tractor plots and those on the tined plots recessed more quickly than those on the ploughed plots. Lack of soil compaction on the gantry plots and continuous vertical fissuring created by the non‐inverting tillage tines resulted in the gantry tined treatment having the fastest drainage response. In the ploughed plots compaction and smearing of the soil at the base of the plough layer restricted the rate of downward movemenl of water. The work indicates that soil management practices can play an important role in the drainage and leaching of aggregated soils.
Simulation modelling of land suitability evaluation for dry season peanut cropping based on water availability in Northeast Thailand: evaluation of the MACROS crop model
Authors: Katawatin R. , Crown P.H. , Grant R.E
Published: February 2007

Abstract. The MACROS crop model was evaluated for its utility to generate information on land suitability for dry season peanut cropping based on water availability at the regional scale in Khon Kaen Province, Northeast Thailand. The model was specific for the condition where crop growth is limited by water stress, and evaluated using both calibration and validation phases in sequence. In the model calibration, data sets from one peanut field experiment were used to calibrate some parameters to obtain the best agreement between experimental and simulated results. The model validation, in this study, consisted of a ‘validation A’, with emphasis on the accuracy and a ‘validation B’, with emphasis on the usefulness and relevance of the model. In the model validation A, data sets from peanut field experiments were used to validate the model under different conditions. Satisfactory agreements were found between the dynamics of observed and corresponding simulated values of shoot dry weight in every condition involved in this validation study. Also the simulated pod yields agree well with the field data. For the validation R, the model was further validated using data from 36 farm trials conducted at 5 different test sites. A high positive correlation (r= 0.91) existed between observed and simulated pod yields. Because of these satisfactory agreements between observed and corresponding simulated values, it was concluded that the model is valid and can be applied to Khon Kaen Province.
Potential climate change effects on the distribution of agricultural grassland in England and Wales
Authors: Rounsevell M.D.A. , Brignall A.P. , Siddons P.A.
Published: February 2007

Abstract. The spatial distribution of agricultural grassland in England and Wales has been assessed using a land evaluation model applied to information describing soils, climate and topography on a 5 × 5 km grid. The model calculates land suitability for grassland from assessments of trafficability/poaching risk and yield class. The spatial distribution of agricultural grassland was modelled for a 30 year climatic baseline (1941–1970) and for incremental changes in temperature and proportional changes in precipitation relative to that baseline.

Model estimates for the current distribution of grassland suitability agree well with observed data of actual grassland distribution. The best suited land occurs in south west England, Wales, the Welsh borders and Cheshire with fragmented areas of well suited land in north west England and on the Pens and Humberhead levels.

The climatic sensitivity analysis suggests that grassland production in England and Wales is resilient to small perturbations in mean temperature (up to +2°C) and precipitation (±10%). The effect of increasing temperature by 1°C is almost completely offset by precipitation increases of 10% resulting in little change to the distribution of grassland suitability. However, greater temperature changes (+ 4°C) have a major influence on the ability of land to support intensively managed grassland because of increased drought stress. Results indicate that a change in the climate comparable with current best estimates for the future would benefit grassland on good quality land at higher altitudes.
Agricultural improvement of cultivated organic soils I. Effects of deep cultivation, liming, irrigation and P‐fertilization on crop yields
Authors: Berglund K.
Published: February 2007

Abstract. Four field experiments were carried out on cultivated shallow fen peat overlying acid gyttja (lake mud) soil. The accessibility of the generally ample supply of physically available water was restricted by a limited root depth caused by low pH and high levels of aluminium in the subsoil. In order to improve the nutrient status and the crop water supply of the soils liming, deep cultivation, P‐fertilization and irrigation were tested in field experiments comprising these four main treatments and their combinations. Liming and P‐fertilization of the topsoil, irrigation and deep cultivation in combination with deep liming improved crop yields. Deep cultivation without liming had a negative effect on yield in most years.
Nitrate leaching from a small catchment in central England
Authors: Cooper D.M. , Roberts G.
Published: February 2007

Abstract. Flow and nitrate concentrations were measured weekly for four years at twelve stream‐water monitoring sites in a catchment in the English Midlands designated as a Nitrate Advisory Area. Farm surveys and satellite images have provided soil and land use information. Measurements show the nitrate load to be dominated by discharge, with large variability due to differing weather conditions from year to year. Within‐year variability in nitrate concentrations is also related to weather conditions, with high concentrations when field capacity is reached if this occurs late in the year. There is also clear evidence of dilution of nitrate during intense storms. The effect of changing weather conditions makes it impossible to identify catchment‐scale changes in leaching due to changes in agricultural practice over a period as short as four years. Measurements from a major spring in the catchment show an increasing trend in nitrate concentrations through the period. There is some evidence that the greatest N leaching to streams in the catchment is associated with intensive grassland on soils which are naturally poorly drained.
Effects of coal derived humic substances on water retention and structural stability of Mediterranean soils
Authors: Piccolo A. , Pietramellara G. , Mbagwu J.S.C.
Published: February 2007

Abstract.The potential for using coal‐derived humic substances to improve the available water holding capacity (AWC) and aggregate stability of typical Mediterranean soils was evaluated in the laboratory using an agricultural surface (0–20 cm) soil from each of three regions of Italy, (Sicily, Tuscany and Venetia) and five rates of humic acids (HA), 0,0.05,0.10,0.50 and 1.00 g/kg. There were significant (P< 0.05) differences between the field capacity (FC), permanent wilting point (PWP), and available water capacity (AWC) values of the controls and those treated with 0.05 g/kg of the HA. Beyond this rate, differences in these properties were not significant. At the 1.00 g/kg HA rate, the relative improvements in AWC over the three controls were 30%, 10% and 26%. Low rates (0.05 to 0.10 g/kg) of HA were also needed to obtain a 40 to 120% improvement in aggregate stability of these soils relative to the controls. These results indicate that the addition of highly humified organic matter such as coal‐derived humic substances can improve the structural and water retention properties of degraded arable soils. However, since there is not yet any direct evidence that these humic materials can ameliorate soils under field conditions, field studies will be needed to validate these results.
The influence of organic nitrogen mineralization on the management of agricultural systems in the UK
Authors: Shepherd M.A. , Stockdale E.A. , Powlson D.S. , Jarvis S.C.
Published: February 2007

Abstract. The understanding of nitrogen mineralization is central to providing good advice to ensure that nitrogen (N), from whatever source, is utilized by crops as efficiently as possible to minimize pollution. We have reviewed how mineralization is accounted for in current advice. It is clear that there is at least a qualitative understanding of the effects of soil and crop management on N mineralization and N supply, which has enabled the development of Codes of Good Agricultural Practice and fertilizer recommendations systems, based on sound scientific principles. However, to refine advice there is a need for a better quantitative understanding.

Although soil organic matter (SOM) is a major source of N for crops, we are unable adequately to predict fertilizer requirement as affected by mineralization of SOM. Nitrogen returns from crop residues can vary considerably between fields; the provision of better field specific advice is restricted by our inability accurately to quantify this variability. The qualitative controls on the amount and timing of N release from ploughed grass are known, but better quantification of mineralization/immobilization over both the short‐ and long‐term and better understanding of the relationship with sward age, inputs and management are essential. Much N can also be released from pasture and lost to the environment, especially where long‐term leys have been grazed and there is a need to quantify the changing balance of mineralization and immobilization with the age of sward and N input. Whilst the overall principle of cultivation affecting mineralization is well known and appreciated, little is known about the mechanisms and quantification is only possible for a comparison of such extremes as ploughing and direct drilling.
The impact of erosion on the productivity of a Ferralsol and a Cambisol in Santa Catarina, southern Brazil
Authors: Tengberg A. , Stocking M. A. , Veiga M. Da
Published: February 2007

Abstract. The impact of soil erosion on soil productivity was estimated for a Rhodic Ferralsol and a Eutric Cambisol in Santa Catarina, southern Brazil. Over equivalent periods, total soil losses were an order of magnitude different (868 and 68 t/ha respectively on the bare soil control), yet the impact on maize yield per tonne of soil lost was far greater at the Cambisol site with less erosion. Similar interesting contrasts between sites were found for the other measures of impact with decline in pH and phosphorus and increase in free aluminium being the most obvious induced soil differences. The results demonstrate the variable nature of erosion impact according to soil type and they highlight the importance of examining a number of measures of impact before pronouncing on the sustainability of any particular agricultural practice.
Evaluating the land use potential of gypsiferous soils from field pedogenic characteristics
Authors: Verheye W. H. , Boyadgiev T. G.
Published: February 2007

Abstract. Although gypsiferous soils cover approximately 100 million ha in the world, it is only in the past two decades that their pedogenic and agronomic properties have been better understood and their classification improved. There is still no method to assess adequately their production potential.

This paper focuses on gypsum accumulation forms as diagnostic criteria for a rapid soil suitability appraisal in the field. Pseudomycelia, gypsum spots, powdery coatings and other localized in situ precipitations usually indicate soils with less than 15% gypsum. Depending on their intensity and depth of occurrence in the root zone, they define a soil environment which is suitable for semi‐sensitive and semi‐tolerant crops. Continuous gypsum accumulations characterize soils or horizons with high (e.g. more than 25%) gypsum contents, and these can be used only for tolerant crops.

The land use potential of gypsiferous soils is primarily determined by: (a) the depth of the impermeable layer, (b)the gypsum content within the root zone, and (c) the crop tolerance level. A method is proposed to assess the land suitability of gypsiferous soils on the basis of these criteria.
Effects of repeated straw incorporation on crop fertilizer nitrogen requirements, soil mineral nitrogen and nitrate leaching losses
Authors: Nicholson F. A. , Chambers B. J. , Mills A. R. , Strachan P. J.
Published: February 2007

Abstract. The effects of straw disposal by burning and incorporation on soil and crop nitrogen (N) supply, were investigated on two light textured soils in central (ADAS Gleadthorpe) and eastern England (Morley Research Centre) over the period 1984 to 1995. Nitrogen balance calculations showed that after 11 years of contrasting straw incorporation versus burn treatments, the cumulative N returns in straw were c. 570kg/ha at Gleadthorpe and c. 330 kg/ha at Morley However, these N returns via straw incorporation were not reflected in increased total soil N levels in autumn 1994. There were no differences (P > 0.05) between straw disposal treatments in autumn soil mineral N supply, readily mineralizable N or organic carbon. Similarly, there were no consistent differences between the treatments in terms of crop yield, crop N uptake or optimum fertilizer N rates. Fertilizer N applications of 200 kg N/ha/y increased topsoil organic carbon from 1.18 to 1.28% and total N content from 0.091 to 0.102% on the loamy sand textured soil at ADAS Gleadthorpe, but not at Morley. Previous fertilizer N applications increased the quantity of nitrate‐N leached in drainage water by c. 20 kg/ha at Gleadthorpe and c. 60 kg/ha at Morley overwinter 1994/95, and by 10–20 kg/ha at both sites overwinter 1995/96. There was some indication overwinter 1994/95 that straw incorporation reduced nitrate‐N leaching by 10–25 kg/ha, but there were no differences between treatments overwinter 1995/96.
The influence of vegetation species and plant properties on runoff and soil erosion: results from a rainfall simulation study in south east Spain
Authors: Quinton J. N. , Edwards G. M. , Morgan R. P. C.
Published: February 2007

Abstract. To study the influence of different vegetation species and plant properties on the generation of surface runoff and soil erosion in south east Spain, a series of rainfall simulation experiments was conducted on small (c. 1.5 m2) plots. These were carried out in October 1993 and May 1994 on two sites close to Murcia. Six vegetation types were studied, with some at different stages of maturity, giving a total of nine vegetation treatments and two bare soil treatments. Four replicates of each treatment were exposed to a rainstorm of 120 mm/h for 15 minutes. The results of the experiments show that there are few significant differences in the ability of the vegetation types studied to control runoff or soil erosion. Of the plant properties considered, only plant canopy cover showed a significant relationship with soil loss and runoff with the greatest reduction in soil loss taking place at canopy covers greater than 30%. The implications of this research are that future efforts should be directed at developing ecological successions and revegetation methods which promote a substantial and sustainable canopy cover.
Sewage sludge application to land – a preliminary assessment of the sensitivity of Scottish soils to heavy metal inputs
Authors: Towers W. , Paterson E.
Published: February 2007

Abstract. The projected increase in sewage sludge used on land within many countries in the European Community will provide a major source of entry for several heavy metals into the soil. Although the application rate of sewage sludge to agricultural land is constrained by maximum annual additions of heavy metals, there is a need to know the sensitivity of those soils to heavy metal inputs which are physically suited for application. A rulebased classification using weighted parameters designed to assess the metal binding capacity of soil and the risk of groundwater pollution has been applied to soils data held within the Macaulay Land Use Research Institute's National Soils Inventory The classification uses soil pH, organic matter content, texture and soil colour as a surrogate for iron oxide concentration. The results indicate that some metals, for example cadmium and zinc are potentially more mobile in soils than others such as lead, but that the majority of soils display a strong or very strong binding capacity for all the metals. However this pattern can only be sustained if the soil pH values are maintained at their present values; a fall of one pH unit marks a dramatic shift towards the weak and moderate binding classes. The approach is largely unvalidated but does provide a useful framework for incorporating our mechanistic understanding of processes into wide area soil quality assessments and in identifying future research opportunities.
Estimation of N2‐fixation by grass–white clover mixtures in cut or grazed swards
Authors: Watson C. A. , Goss M. J.
Published: February 2007

Abstract. Formulation of nitrogen balances on farms requires accurate information on all inputs of the nutrient. N2‐fixation by legumes, particularly forage legumes, is an important input which is difficult to measure. Simple regression models have been established from the literature for predicting N2‐fixation by grass–white clover (Trifolium repens) mixtures using dry matter yields.

Linear relationships were obtained between the N2‐ fixation (Nfix) and the extra dry matter production of mixed swards (Md) compared with pure grass swards. Nitrogen fixation was given by Nfix= A + 0.067Md where A is the intercept having a value of 6.8 for cut swards and ‐168.1 for grazed swards. A common slope was adopted because the F statistics showed that slopes fitted separately were not significantly different. The value of the negative intercept represents the supply of N to the grazed sward from soil and excreta‐derived N. The regression equation for the cut sward gave reasonable predictions (r2= 0.953) of values of N2‐fixed for experimental data not used in establishing the relationship. For grazed grass, the approach over‐estimated the N2‐ fixation by an average of 15%.
Soil and land use effects on phosphorus in six streams draining small agricultural catchments in Scotland
Authors: Hooda P. S. , Moynagh M. , Svoboda I. F. , Thurlow M. , Stewart M. , Thomson M. , Anderson H. A.
Published: February 2007

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.
Tropical land use change and soil emissions of nitrogen oxides
Authors: Erickson H. E. , Keller M.
Published: February 2007

Abstract. Increases in the emissions of globally important nitrogen (N) oxide gases have coincided with significant changes in land use in the tropics. Clearing of tropical forests and savannas for agriculture currently represents the most extensive alteration of land cover on the planet. Over the last several decades, N fertilizer use has increased globally, and in China and the developing world, use has recently surpassed that in the developed world. The potential contribution of land‐use change in the tropics to the increase in N oxides is great, yet only a few studies have measured N oxide emissions after tropical land conversion. Our summary of available research shows some conversions to pastures and a few management practices, especially those using N fertilizers, increase emissions beyond those found in undisturbed ecosystems. However, not all studies show unequivocal increases in emissions. Accordingly, we call for a mechanistic understanding of the processes controlling trace gas fluxes to adequately predict under what conditions increased emissions may occur. More measurements are needed to build and test models that may improve management of N fertilizer use in tropical agricultural systems. Given the expected expansion of agriculture and increased use of N fertilizers in the tropics, increased emissions of N oxides from the tropics are likely.
An empirical model for estimating nitrate leaching as affected by crop type and the long‐term N fertilizer rate
Authors: Simmelsgaard S. E. , Djurhuus J.
Published: February 2007

Abstract. An empirical model was developed for prediction of annual average nitrate leaching as affected by the long‐term rate of N fertilization and crop type. The effect of N fertilization was estimated from annual values of nitrate leaching obtained from two Danish investigations of drainage from pipe drains with four rates of N fertilization on a loamy sand and sandy clay loam from 1973‐89. The effect of crop at normal N fertilization was estimated from 147 observations of annual nitrate leaching obtained from field measurements. The nitrate leaching model consists of a relative N fertilization submodel and an absolute submodel for specific combinations of crop, soil and drainage at the normal rate of N fertilization. The relative submodel is Y/YlN= exp[0.7l(N/ N1– I)], where Y is the nitrate leaching (kg N/ha per year) at fertilization rate N, and YIN and N1 are the corresponding values at the normal rate of N fertilization. The relative submodel is valid for cereals, root crops and grass leys fertilized with mineral fertilizer at N/N1 < 1.5, and on the prerequisite that the fertilization rate N has been constant for some years. To illustrate the use of the relative leaching submodel, estimated values of YIN corrected to mean annual drainage for 1970 to 1990 in Denmark for spring cereals and grass on sandy and loamy soils are given as input to the relative leaching submodel. The model can be used for sandy to loamy soils to estimate the mean nitrate leaching over a number of years.
Relationships between soil thermal units, nitrogen mineralization and dry matter production in pastures
Authors: Clough T. J. , Jarvis S. C. , Hatch D. J.
Published: February 2007

Abstract. Nitrogen (N) is of enviromental concern if it leaches or is released as nitrous oxide (N2O,). In order to utilize N efficiently in grazed pasture systems, the fluxes of N from various sources need to be quantified. One flux is N mineralization from organic sources. Previous work has examined incubation and chemical extraction of soils as methods to determine N mineralization potential. This paper re‐examines new and previously published data on net mineralization, with the aim of examining the relationships between soil thermal units, net N mineralization (measured using acetylene incubations) and dry matter production in pastures. Net N mineralization is expressed as N turnover (net N mineralization as a % of total soil N). Relationships are developed between soil thermal units, dry matter production, and N turnover. These relationships have potential in advising farmers on potential N mineralization from soil organic matter. A second use of such relationships is the modelling of N transformations in pasture systems. Further work should explore the effect of soil moisture on such relationships and examine the relationship between soil thermal units and uptake of N by pasture.
Effect of nitrogen inputs to cereals on nitrate leaching from sandy soils
Authors: Lord E. I. , Mitchell R. D. J.
Published: February 2007

Abstract. The effect of nitrogen fertilizer inputs to cereal crops on nitrate leaching after harvest was tested on 21 experiments on sandy soils in England. At small nitrogen fertilizer rates leaching increased very little with increasing inputs, while at high rates more than half of any additional nitrogen could be accounted for as increase in nitrate leached. In many cases the response fitted two straight lines. Nitrogen offtake in grain also fitted two straight lines, with a form which complemented the leaching response. The gradient averaged 0.52 kg N in grain for every additional 1kg N applied below the break point, but only 0.05 kg/kg above. The break points were generally close to or above the economic optimum N input. The effect of inputs on leaching could he quantitatively related to nitrogen offtake in grain, assuming a constant ratio of nitrogen in grain to total nitrogen uptake. The results show that fields receiving N inputs in excess of the economic optimum cause a disproportionately large nitrate loss. However because of uncertainty in predicting the break point in advance, modest further reduction in leaching will occur by reducing inputs to somewhat below the expected economic optimum.
The Unsung Perils of Peripheral Arterial Disease: A Malady in Search of a Patient
Authors: Dunbar Richard L. , Mohler Emile R.
Published: February 2007

Peripheral arterial disease (PAD) is increasingly recognized as a strong predictor of mortality and morbidity from atherosclerotic events, especially from coronary heart disease. Since vascular disease remains the most common cause of death in the world, the substantial prevalence, ease of diagnosis, and ominous prognosis have increased interest in PAD among the prevention community. The association with coronary heart disease is strong enough that for prevention purposes, PAD should be considered a high‐risk condition that demands aggressive therapy to reduce incident vascular events. Unlike other forms of atherosclerotic disease, PAD is easily diagnosed in the outpatient clinic noninvasively, using the ankle brachial index. Because its diagnosis can thus be seamlessly integrated into the routine clinical encounter, the ankle brachial index has emerged as a tool for global risk assessment. This article will review the relationship between PAD and other vascular disease, emphasizing the role of PAD in prevention efforts.
A Meta‐Analysis of the Effect of Thiazolidinediones on Blood Pressure
Authors: Qayyum Rehan , Adomaityte Jurga
Published: February 2007

In epidemiologic studies, insulin resistance is associated with hypertension. Thiazolidinediones (TZDs) are antidiabetic agents that decrease insulin resistance. Multiple clinical trials have evaluated the effect of TZDs on blood pressure (BP) with inconsistent results. The aim of this study was to estimate the effect of TZDs on BP. The authors searched PubMed for clinical trials published in English. A total of 37 clinical trials that reported a change in BP were included in the analysis. Trials with independent‐group design and trials with pre‐post design were evaluated separately. When compared with baseline, TZDs lowered systolic BP by 4.70 mm Hg (95% confidence interval, −6.13 to −3.27) and diastolic BP by 3.79 mm Hg (95% confidence interval, −5.82 to −1.77). When compared with placebo, TZDs lowered systolic BP by 3.47 mm Hg (95% confidence interval, −4.91 to −2.02) and diastolic BP by 1.84 mm Hg (95% confidence interval, −3.43 to −0.25). Thus, TZDs lower both systolic and diastolic BP, albeit the BP‐lowering effect is small and may not be of clinical significance.
The Pleiotropic Effects of Angiotensin Receptor Blockers
Authors: Chrysant Steven G. , Chrysant George S.
Published: February 2007

The angiotensin receptor blockers (ARBs) are very effective and safe antihypertensive drugs. They exert their antihypertensive effect through blockage of the angiotensin II, type 1 receptor and quite possibly through stimulation by angiotensin II of the unoccupied type 2 receptor. Besides hypertension, the ARBs have been found recently to be of value in the treatment of heart failure and diabetic nephropathy. In addition, ARBs have emerged lately as being very effective and perhaps superior to other antihypertensive drugs in the prevention of de novo or recurrent strokes. Other actions that may account for their stroke‐protective effects include their antiatherogenic, antidiabetic, antiplatelet aggregating, hypouricemic, and atrial antifibrillatory actions. All these actions make the ARBs a true pleiotropic class of drugs. Each of the foregoing effects will be discussed briefly in this concise review.
Resistant or Difficult‐to‐Treat Hypertension
Authors: Calhoun David A.
Published: February 2007

Resistant hypertension, defined as uncontrolled hypertension on three medications, is becoming an increasingly common problem. In most cases, blood pressure remains elevated because of persistently high systolic blood pressure levels. Common characteristics of patients with resistant hypertension include older age, obesity, excessive dietary salt ingestion, and presence of sleep apnea. The evaluation of patients with resistant hypertension is focused on identifying contributing and secondary causes of hypertension. Treatment should include both lifestyle changes (weight loss, exercise, dietary salt restriction) and the use of effective multidrug regimens, including a diuretic. Recent data indicate that aldosterone antagonists may be effective when added to existing antihypertensive regimens even in the absence of primary aldosteronism.
Drug‐Induced Metabolic Syndrome
Authors: Wofford Marion R. , King Deborah S. , Harrell T. Kristopher
Published: February 2007

The metabolic syndrome is a cluster of risk factors associated with an increased risk for cardiovascular disease and type 2 diabetes. Based on data from 1988 to 1994, it is estimated that 24% of adults in the United States meet the criteria for diagnosis of the metabolic syndrome. The use of certain medications may increase the risk of the metabolic syndrome by either promoting weight gain or altering lipid or glucose metabolism. Health providers should recognize and understand the risk associated with certain medications and appropriately monitor for changes related to the metabolic syndrome. Careful attention to drug choices should be paid in patients who are overweight or have other risk factors for diabetes or cardiovascular disease.
A Systematic Review of the Effects of Home Blood Pressure Monitoring on Medication Adherence
Authors: Ogedegbe Gbenga , Schoenthaler Antoinette
Published: February 2007

Home blood pressure monitoring (HBPM) improves blood pressure control, but little is known about its effects on medication adherence. The authors conducted a systematic review of the published literature on the effects of HBPM on medication adherence. Of 440 abstracts and citations reviewed, 11 randomized control trials met predefined criteria. Six of the 11 randomized controlled trials reported statistically significant improvement in medication adherence; 84% of these were complex interventions involving the use of HBPM in combination with other adherence‐enhancing strategies such as patient counseling by nurses, pharmacists, or a telephone‐linked system; patient education; and the use of timed medication reminders. Interventions conducted in primary care settings were not effective compared with those that occurred in hospital‐based clinics or nonclinical settings. The data on the effects of HBPM on patients' medication‐taking behavior are mixed. Future studies should investigate the independent effects of HBPM in primary care practices where the majority of hypertensive patients receive their care.
Hypertensive Emergencies
Authors: Moser Marvin , Izzo Joseph L. , Bisognano John
Published: February 2007

Following a hypertension symposium in Rochester, NY, in October 2005, a roundtable was convened to discuss hypertensive emergencies. Dr. Marvin Moser, Clinical Professor of Medicine at the Yale University School of Medicine, New Haven, CT, moderated the session, which included Dr. Joseph L. Izzo, Jr., Professor of Medicine at the State University of New York at Buffalo, Buffalo, NY, and Dr. John Bisognano, Associate Professor of Medicine at the University of Rochester School of Medicine, Rochester, NY.
Effects of the Angiotensin II Receptor Blockers Telmisartan vs Valsartan in Combination With Hydrochlorothiazide 25 mg Once Daily for the Treatment of Hypertension
Authors: White William B. , Punzi Henry A. , Murwin Debra , Koval Stephen E. , Davidai Giora , Neutel Joel M.
Published: February 2007

To attain recent goals of blood pressure (BP) control, multiple drug therapy combinations are required, including higher doses of thiazide diuretics in combination with other classes of antihypertensive drug therapy. Thus, the authors evaluated the antihypertensive effects of telmisartan vs valsartan when combined with hydrochlorothiazide (HCTZ) 25 mg in a large (N=1066), placebo‐controlled trial in patients with stage 1 or 2 hypertension. The primary end points were the changes from baseline in seated diastolic and systolic BP at the end of the 8‐week treatment period. Safety end points included adverse events, changes in laboratory parameters, and pulse rate. Changes from baseline in BP following telmisartan‐HCTZ (−24.0/−17.6 mm Hg) were significantly greater than both placebo (−4.4/−6.8 mm Hg) and valsartan‐HCTZ (−21.2/−16.1 mm Hg) (vs placebo, P<.001 for systolic and diastolic BP; vs valsartan‐HCTZ, P=.004 for systolic BP and P=.019 for diastolic BP). The total number of patients with at least 1 adverse event reported were similar among the 3 treatment groups (placebo, 49%; telmisartan‐HCTZ, 43%; and valsartan‐HCTZ, 38%). In conclusion, telmisartan‐HCTZ at doses of 80/25 mg lowered both systolic and diastolic BP to a greater extent than valsartan‐HCTZ at doses of 160/25 mg. These data support using a higher dose of a thiazide diuretic (25 mg) with a long‐acting angiotensin receptor blocker as a useful strategy for improving hypertension control.
Prevalence of the Metabolic Syndrome in the United States National Health and Nutrition Examination Survey 1999–2002 According to Different Defining Criteria
Authors: Cheung Bernard M.Y. , Leung Ong Kwok , Man Yu Bun , Wong Louisa Y.F. , Lau Chu‐Pak , Lam Karen S.L.
Published: February 2007

The authors studied the prevalence of the metabolic syndrome in the 1999‐2002 National Health and Nutrition Examination Survey (NHANES) according to the World Health Organization, National Cholesterol Education Program (NCEP), and International Diabetes Federation (IDF) definitions. There was 92.9% agreement between the NCEP and IDF definitions. The IDF prevalence was higher (p=0.001) due to more men fulfilling its criteria than the NCEP's (39.9+1.7% vs. 33.6+1.6%; p=0.007). If central obesity were not a prerequisite, the IDF prevalence would increase slightly to 40.3+1.1 %. Subjects categorized as having the metabolic syndrome under IDF but not NCEP tended to be men, younger, and leaner. Their prevalence of self‐reported coronary heart disease was not significantly different from that of other metabolic syndrome patients. Whether waist circumference is a prerequisite does not affect the diagnosis of the metabolic syndrome in the United States. The IDF definition identifies additional individuals at risk for cardiovascular disease.
Effects of Monotherapy and Combination Therapy on Blood Pressure Control and Target Organ Damage: A Randomized Prospective Intervention Study in a Large Population of Hypertensive Patients
Authors: Tedesco Michele Adolfo , Natale Francesco , Calabro Raffaele
Published: February 2007

This prospective, randomized trial evaluated the effect of monotherapy and different combination therapies on cardiovascular target organ damage and metabolic profile in 520 hypertensive patients. Patients were allocated to a single agent: carvedilol 25 mg, amlodipine 10 mg, enalapril 20 mg, or losartan 50 mg (groups C, A, E, and L, respectively). After 2 months (level 2), nonresponders received a low‐dose thiazide diuretic, and after 4 months (level 3), amlodipine (groups E, C, and L) and carvedilol (group A). Twenty‐four‐hour blood pressure was significantly lowered in all treatment groups. Blood pressure control was more pronounced in patients receiving two or three drugs. At the end of the study, the carotid intima‐media thickness decreased in group L (P<.01), left ventricular mass index in groups E and L (P<.05 and P<.001, respectively), with a concomitant reduction in cholesterol in group L (P<.03). Diastolic function improved significantly in group L (P<.05). This study describes the need to control blood pressure with two or more drugs in most hypertensive patients and illustrates good clinical outcomes, independent of blood pressure lowering, using combination therapy with losartan, low‐dose thiazide, and amlodipine.
Elevated Endothelin‐1 Levels Are Associated With Decreased Arterial Elasticity in Hypertensive Patients
Authors: Ergul Adviye , Jupin Dena , Johnson Maribeth H. , Prisant L. Michael
Published: February 2007

Endothelin‐1 stimulates collagen synthesis and is increased in hypertension, but its effect on collagen degradation remains unknown. The current study tested the hypothesis that elevated endothelin‐1 levels are associated with decreased collagenase activity, markers of collagen degradation, and arterial compliance in hypertensive patients. Normotensive (n=10) and hypertensive (n=13) patients who were not on any antihypertensive medication were recruited, and small and large artery elasticity index, systemic vascular resistance, pulse pressure, and blood pressure were determined using blood pressure waveform analysis. Large artery elasticity index and collagen degradation products were decreased whereas endothelin‐1, systemic vascular resistance, and pulse pressure were elevated in hypertensive patients. Plasma endothelin‐1 was negatively correlated with a cross‐linked C‐terminal telopeptide of collagen type I, a collagen degradation marker (r=−0.43; p=0.04), collagenase matrix metalloproteinase‐1 (r=−0.48; p=0.02), and large artery elasticity (r=−0.45; p=0.03) and positively correlated with pulse pressure (r=0.68; p=0.0005). These results suggest that endothelin‐1 contributes to decreased arterial compliance in hypertension via inhibition of collagen degradation.
Influence of Sympathetic Activity on Blood Pressure and Vascular Damage Evaluated by Means of Urinary Albumin Excretion
Authors: Mena‐Martín Francisco J. , Martín‐Escudero Juan C. , Simal‐Blanco Fernando , Arzua‐Mouronte Delfín , Sanz Juan J. Castrodeza ,   for the Hortega Study Investigators
Published: February 2007

To analyze the influence of sympathetic activity on blood pressure (BP) and its effects on urinary albumin excretion (UAE), the authors carried out a cross‐sectional study in their local health coverage area. The following variables were monitored in a representative sample of the general population made up of 495 individuals: anthropometric parameters; blood glucose, creatinine, and lipid levels; 24‐hour urinary albumin, norepinephrine, and epinephrine excretion; and BP of patients with known hypertension and newly discovered BP ≥140/90 mm Hg, evaluated by ambulatory monitoring. In the multivariate analysis, only gender, systolic BP, and UAE were associated with norepinephrine levels; only gender, systolic BP, and body mass index were associated with epinephrine. After excluding those patients with chronic kidney disease, the multivariate analysis showed a strong association between UAE ≥30 mg/d and elevated norepinephrine and epinephrine levels. The authors concluded that in the subject population there is an association between elevated adrenergic activity and higher UAE, independent of factors such as age and BP.
Retracted: Effects of Whey Peptides on Cardiovascular Disease Risk Factors
Authors: Pins Joel J. , Keenan Joseph M.
Published: February 2007

Previous studies have shown that peptides derived from milk proteins can improve blood pressure. Therefore, the authors tested the blood pressure‐lowering effects of a hydrolyzed whey protein supplement rich in bioactive peptides. In a 6‐week controlled study, 30 prehypertensive or stage 1 hypertensive subjects (blood pressure ≥120/80 mm Hg and ≤155/95 mm Hg) were randomized to receive 20 g/d of either a hydrolyzed whey protein (active treatment) or an unmodified whey protein (control treatment). Blood pressure, blood lipids, safety measures, side effects, and diet were evaluated throughout the trial. After completion of treatment, a 4‐week follow‐up was conducted. There was a mean reduction of 8.0+3.2 mm Hg in systolic blood pressure (P<.05) and of 5.5±2.1 mm Hg in diastolic blood pressure (P<.05) in the treatment group compared with the control group. Low‐density lipoprotein cholesterol and high‐sensitivity C‐reactive protein were significantly improved by treatment. Whey‐derived peptides might be a viable treatment option for prehypertensive and/or stage 1 hypertensive populations.
Incidence and Predictors of Angioedema in Elderly Hypertensive Patients at High Risk for Cardiovascular Disease: A Report From the Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial (ALLHAT)
Authors: Piller Linda B. , Ford Charles E. , Davis Barry R. , Nwachuku Chuke , Black Henry R. , Oparil Suzanne , Retta Tamrat M. , Probstfield Jeffrey L. ,   for the ALLHAT Collaborative Research Group
Published: February 2007

Angioedema is a rare, potentially life‐threatening condition that has been associated with angiotensin‐converting enzyme inhibitors since their introduction in the 1980s. The Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), the largest antihypertensive study conducted to date, randomized 42,418 participants to a diuretic (chlorthalidone), a calcium channel blocker (amlodipine), an angiotensin‐converting enzyme inhibitor (lisinopril), or an α‐blocker (doxazosin). Patients who developed angioedema were compared for baseline characteristics and changes in antihypertensive drug administration. Fifty‐three participants developed angioedema during active follow‐up: 55% were black, 60% men, and 70% were assigned to lisinopril (including 62% of black participants with angioedema), 15% to chlorthalidone, 9% to doxazosin, and 6% to amlodipine. Six percent occurred within a day of randomization and 23% within the first week. Over half did not have an increase in their assigned (blinded) antihypertensive drug before angioedema onset; 3 (6%) had a dose increase within a week before onset. One patient died following an angioedema episode. The occurrence of angioedema in the angiotensin‐converting enzyme inhibitor arm corresponds with previously reported angioedema–angiotensin‐converting enzyme inhibitor associations.