bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil degradation processes and their control in Hungary
Authors: Várallya György
Published: February 2007

Soil degradation is usually a complex process in which several features of soil deterioration can be recognized. Soil degradation may lead to the loss of land or soil; limitations to normal soil functions; decrease of soil fertility and ‘productive capacity’.

The main soil degradation process are: (1) soil erosion by water and wind; (2) Development of extreme soil reaction (acidification; salinization/alkalization); (3) physical degradation (structural destruction; compaction; extreme moisture regime); (4) biological degradation; (5) unfavourable changes in the nutrient regime; (6) decrease of buffering capacity (leading to pollution, toxicity).

Soil degradation is not an unavoidable consequence of intensive agriculture and social development. Most of the processes and their unfavourable consequences can be controlled, prevented, eliminated, or at least moderated.

A rational strategy of efficient soil degradation control should be based on a system involving the following (consecutive) steps: (a) registration of facts and consequences; (b) analysis of reasons, processes, influencing factors and their mechanisms; (c) determination of the theoretical, real, rational and economic possibilities for control; (d) prediction of the potential impacts of these control alternatives; (e) elaboration and extension of technologies for the optimum alternatives.

The present status of soil degradation processes in Hungary is briefly summarized in this paper and the possibilities for control are reviewed, with special regard to soil erosion, salinization/alkalization, acidification and physical degradation (compaction, structure destruction). Based on detailed and comprehensive information on soils (thematic maps of various scales; computerized geographical soil information system) the potential future development of various soil degradation processes is forecast and technologies are elaborated and recommended for use in Hungarian agriculture to prevent soil degradation.
Land use, deforestation and reforestation in the Zambian Copperbelt
Authors: Chidumayo E. N.
Published: February 2007

Temporal and spatial changes in land use, vegetation cover, deforestation and reforestation in the Zambian Copperbelt were studied using a combination of aerial photograph analysis, literature review and inquiries among relevant government institutions.

The study showed that between 1937 and 1984 loss of natural woodlands in the Copperbelt of Zambia (total area of Copperbelt: 9,615 km2) amounted to 41 per cent woodland area (8,419 km2). The major causes of this deforestation are woodfuel collection (for firewood and charcoal), cultivation and replacement of natural woodland with forest plantations. These accounted for 38 per cent, 37 per cent and 15 per cent of the total deforestation, respectively. Before 1962 the copper mining industry used large quantities of firewood to generate electricity and this resulted in the loss of 150,413 ha of woodland between 1937 and 1961. When the mining industry switched to hydroelectricity, urban households became the major users of woodfuel. The urban population in the Copperbelt increased from 0.412 million in 1960 to 1.400 million in 1984 and its consumption of woodfuel led to the deforestation of at least 89,436 ha between 1962 and 1984.

Deforested areas are left to regenerate naturally. However, due to poor management about 34 per cent of the area deforested before 1962 has failed to regenerate. Although 50,200 ha have been reforested with exotic trees, only 5,020 ha of this is on land previously deforested. Thus only about 10 per cent of reforestation efforts have contributed to the rehabilitation of damaged land. Ninety per cent of the reforestation has actually replaced standing indigenous woodland.

Uncontrolled bushfires have destroyed forest plantations and have also caused the failure of woodland regeneration in deforested areas. These observations indicate that if forest resources in the Copperbelt of Zambia are to be properly managed it will be necessary:

to effectively regulate land use changes and;

to control bushfires.
Assessing the sustainability of agricultural land in Botswana and Sierra Leone
Authors: Biot Y. , Sessay M. , Stocking M.
Published: February 2007

Land degradation processes, such as soil erosion, which threaten the sustainability of agricultural production have been studied for many years. While research progresses on the processes, little advance has been ade on translating results into terms which can be used directly in the design of appropriate and economically justified forms of soil conservation and land husbandry.

Research by the authors has shown how soil erosion affects the potential of land to produce crops. Simple models have been developed which provide a first approximation of the impact of soil erosion on future production, to be used as a baseline against which the benefits of soil conservation can be compared. The concepts of soil life and residual suitability have been developed as a measure of the sustainability of the production system considered. In this paper a simple experimental technique to derive the future production and the residual suitability of land is proposed.

The method is based on the principle of sequential testing and uses a simple graphical technique to translate information on production and erosion into a crop production forecast. The soil life or residual suitability of land is derived from the minimum allowable crop production which depends on socio‐economic criteria. In case the minimum allowable production level cannot be reliably estimated, the concept of production ‘half‐life’ is introduced as a relative measure of sustainability. The method and its applications are illustrated using examples from Botswana and Sierra Leone.
African soil erosion — nature undone and the limitations of technology
Authors: Millington A. C. , Mutiso S. K. , Kirby J. , O'keefe P.
Published: February 2007

A wide range of mechanical soil conservation techniques commonly used in Africa are reviewed in a politico‐economic framework. Three factors within this framework play a significant role in the adoption of mechanical soil conservation techniques. These are: (a) land considerations, such as land availability and tenure, and farm size; (b) capital and labour constraints; and (c) access to, and functioning of, institutions.

Hypotheses which are concerned with the relationships between these factors and the likelihood of farmers adopting soil conservation techniques are introduced. Case studies drawn from Kenya, Lesotho, Malawi, Swaziland and Sierra Leone, as well as from Jamaica, are used to test these hypotheses in relationship to such techniques as terracing, grass strip cultivation, bunding, and contour cultivation. Greater reliance on local knowledge and indigenous soil conservation techniques seems to provide the best solution to the introduction of mechanical soil conservation techniques.
Impacts of environmental change on sustainable food production in Southwest Ontario, Canada
Authors: Brklacich M. , Smit B. , Bryant C. , Dumanski J.
Published: February 2007

A sustainable food production system may be defined as an agri‐food sector which over the long term can simultaneously maintain environmental quality, produce a sufficient food supply and provide adequate rewards to primary producers. This paper investigates the implications of two forms of environmental change for sustainable food production in Southwest Ontario, a major agricultural region in Canada. A modified version of the Universal Soil Loss Equation was employed to estimate long‐term erosion, whereas an altered climate was derived from a general circulation model. Crop productivity models were used to estimate the impacts of modified environmental conditions on yields. Mathematical programming models were used to estimate economic viability and food production capacity given these changed conditions. Soil erosion combined with a climatic warming induced by a doubling of atmospheric concentrations of CO2 or its equivalent would contribute to severe declines in resource quality, and result in declines of 18 per cent to 35 per cent in average yields for major grains and oilseeds. On lands with a relatively high natural risk to erosion, the yield‐reducing impacts of erosion and a climatic warming would reduce profits from cash grain farming by 26 per cent, and increase concern about the economic viability of these enterprises. Environmental change would reduce the region's food production potential to 86 per cent of current production levels, and possibly endanger the security of its food supplies. These findings suggest the need to explore strategies which would either prevent future environmental change or mitigate its adverse impacts.
Desert: A prototype expert system to advise on land degradation control
Authors: Balachandran C. S. , Fisher P. F.
Published: February 2007

Land degradation is a collection of processes causing the removal of land from agricultural productivity. Four major processes can be identified: soil erosion by water and wind, soil salinization, and vegetation degradation. Much knowledge exists on how these processes may be combated and ameliorated; however, it is in the minds of a relatively few, widely dispersed experts. The authors have developed a prototype computer‐based expert system (DESERT) which provides advice on strategies for control of land degradation. The knowledge was acquired from experts by interviews. The knowledge was then formulated into two components. The first component enables identification of possible technical solutions, while the other imposes socio‐economic and physical constraints on these technical solutions. Thus, a set of acceptable solutions is formulated. The results are presented here as a proof of concept in an attempt to stimulate further development. Later versions of the program will include problem diagnosis components, as well as a mechanism for prioritizing recommendations.
Field measurement of the sheltering effect of vegetation on erodible land surfaces
Authors: Stockton P. H. , Gillette D. A.
Published: February 2007

Natural vegetation on erodible land surfaces, such as the loose sandy soils found in the southwestern United States and in Soviet Central Asia, absorbs part of the wind momentum flux (stress) and thus protects the erodible soil to a degree that depends on the geometry of plant distribution and profile. The sheltering effect of natural plants may be expressed as the ratio, R, of threshold friction velocity for the bare soil (determined in the laboratory or in specially prepared areas of bare soil in the field) to that for the naturally vegetated surface. We used new automated instrumentation to detect erosion thresholds in locations where erosion events are widely separated in time. Measured values of R were low for our most vegetated sites and nearer unity for the sparsely vegetated site.
Climate change and soil erosion on agricultural land in england and wales
Authors: Boardman J. , Evans R. , Favis‐Mortlock D. T. , Harris T. M.
Published: February 2007

To assess the effects of climate change on soil erosion we need to model changes in rate, frequency and extent of erosion. Present day rates of soil erosion for agricultural land in England and Wales are known from a national monitoring scheme and also from a local one. The latter, for the South Downs, covers a seven‐year period and includes climatic data. This shows a strong correlation between total erosion and a Rainfall Index. The availability of these databases allows us to use existing models such as EPIC and an Expert System to predict erosion rates for postulated warmer and wetter (winter) conditions. EPIC is particularly suitable for specific sites where detailed data exists and crop yield implications can also be modelled. A rule‐based Expert System approach allows us to examine erosion rates at a different scale across the landscape. We postulate that water erosion rates on arable land in the lowlands will increase markedly in severity, frequency and extent especially if land use changes. In the uplands predicted climatic warming suggests a longer growing season and fewer frosts: these may lead to a decrease in erosion of overgrazed eroding slopes. Increases in erosion rates are not inevitable if policy decisions are taken and implemented in good time.
The effect of simulated runoff on the erosion of gypsiferous soils
Authors: Navas A.
Published: February 2007

The effect of runoff generation on the erosion of gypsiferous soils under different experimental conditions was investigated by applying simulated rainfalls of 48 and 58 mm h−1 to experimental plots exhibiting representative characteristics of these soils. The 45 experiments indicate differing erosive behaviour as test conditions varied. Suspended gypsum yields ranged from 0‐3.9 gm−2 h−1 the higher values occurring with the steeper slopes and dry soil conditions. The differences among the soils tested were mainly due to variations in underlying rock outcrop, whilst within each soil type, slope was the most important variable. Transport of suspended gypsum by runoff is inversely related to rock outcrop, and positively related to slope. The highest erosion rates are registered in Gypsic Calcisols, followed by Gypsic Calcisols (lithic phase), while production of suspended gypsum is not verified for Dystric Leptosols. By transporting gypsum particles down‐slope, runoff is probably responsible for the dynamic evolution of gypsiferous hillslopes as well as the genetic evolution of the studied soils.
Grass mixtures for afforested opencast spoils in South Wales
Authors: Moffat A. J. , Roberts C. J.
Published: February 2007

An experiment that investigated the establishment of seven grass and legume seed mixes on opencast coal mining spoil in South Wales is described. After three years, mixtures containing Poa pratensis and Festuca rubra var. rubra were the most successful in covering the spoil; the ‘Johnson JR33’ seed mix proved the best of those commercially available that was tested. Tree growth was not detrimentally affected by the establishment of a grass ground cover. Erosion was not an important process at the experimental site, though slumping occurred locally from plough ridge to plough furrow.
Calibration of caesium‐137 measurements to provide quantitative erosion rate data
Authors: Walling D. E. , Quine T. A.
Published: February 2007

The caesium‐137 technique for investigating rates and patterns of soil loss has now been successfully applied in a wide range of environments. However, some uncertainty still surrounds the ability of the technique to provide quantitative estimates of rates of erosion. The wide range of calibration relationships that have been employed by individual workers to derive erosion rates from estimates of the amount of 137Cs (caesium‐137) lost from the soil profile, emphasize the uncertainty involved. Existing calibration procedures, involving both empirical relationships and theoretical models and accounting procedures are reviewed and their limitations and inconsistencies are identified. Further research is required in this important area, if the clear potential of the caesium‐137 technique is to be fully realized.
Trends in natural resource use and prospects for sustainable resource management in Kenya's Arid and Semiarid Lands
Authors: Darkoh M. B. K.
Published: February 2007

This paper describes the environmental problems facing the development of Kenya's Arid and Semiarid lands (ASAL) today. The problems arise because of a rapidly declining resource base in the ASAL as a result of overexploitation and misuse, following basic land use conflicts. The extent of the overutilization or resource damage is not well known and varies a great deal from one agroecological zone to another and from resource to resource in the ASAL; those most affected include: soil, water, range, forest, livestock and wildlife. As a result of increased population growth in the ASAL, these resources are under stress. This paper argues that many of the environmental problems in the ASAL cannot be solved if the development programme does not address the needs of the people who live in the ASAL. There is a need to shift the objective of ASAL development from a preoccupation with economic growth and the idea that the ASAL should make a contribution to GNP through interregional trade and export to sustainable development that enables the communities in the ASAL to support themselves at as good a standard of living as possible. The last part of this paper outlines a strategy to promote such sustainable development.
Amelioration of a calcareous saline‐sodic soil by gypsum and forage plants
Authors: Ahmad N. , Qureshi R. H. , Qadir M.
Published: February 2007

A field experiment was carried out at the University of Agriculture, Faisalabad (Pakistan) during 1988–90 to evaluate the comparative efficiency of chemical and biological methods for the reclamation of a calcareous saline‐sodic soil (pHs

pHs = pH of saturated soil paste

= 8.2–8.6; ECe

ECe = Electrical conductivity of the saturation extract

= 7.4–9.0 dS m−1; SAR

SAR = Sodium adsorption ratio

= 55.6–73.0 for upper 30 cm layer). Five treatments were assessed, three involved cropping: sesbania (Sesbania aculeata), sordan (Sorghum bicolor x Sorghum sudanese), and kallar grass (Leptochola fusca) and two were non‐cropped (control and gypsum at 100.0 per cent GR‐15·0 cm) were employed. Water of low electrolyte concentration (EC = 0.27 dS m−1) was used for irrigation and leaching. Sesbania and kallar grass were found to be effective biotic materials for soil reclamation. These plant species produced substantial biomass and also improved the soil environment by lowering the EC and SAR of the soil. Sordan was relatively less‐effective due to its sensitivity to high temperature and sodicity during germination and early seedling stages. After two cropping seasons, wheat (cultivar LU 26S) was sown as a test crop. Efficiency of treatments as indicated by wheat grain yield was in the order: sesbania = gypsum > kallar grass > sordan > control.
Deforestation trends in the Atlantic Zone of Costa Rica: A case study
Authors: Veldkamp E. , Weitz A. M. , Staritsky I. G. , Huising E. J.
Published: February 2007

In this study we have tried to link a quantitative inventory of deforestation to possible factors driving forest clearing, like accessibility and soil quality. The Study Area covered 395 km2 in the Atlantic Zone of Costa Rica. Basic information came from aerial photographs taken in 1952, 1960, 1971 to 73, 1981 and 1984. Photo interpretations were digitized and processed with the help of a monoplotting programme. Three phases in deforestation were distinguished:

The period before 1960, characterized by a gradual increase in the rate of deforestation, with preferential clearing along rivers and on fertile soils.

The period 1960‐1972. This period shows an increased clearing rate caused by a new centre of colonization, Cariari. Furthermore, banana plantations entered the area and main roads were constructed. Deforestation took place preferentially along roads and on fertile soils.

In the period 1972‐1984 the remaining forest ‘islands’ were cleared at an accelerated rate. This was because only small areas of forest were left by this period. Also between 1972 and 1984 the fertile soils were cleared most rapidly.
Effects of controlled grazing on a degraded dwarf shrub, annual grass semidesert vegetation type of northwestern Kenya
Authors: Oba G.
Published: February 2007

A degraded dwarf shrub, annual grass semidesert vegetation type in Turkana, northwestern Kenya, was protected from livestock grazing from October 1985 to December 1990. The effects of controlled grazing on plant cover, litter cover and bare ground were monitored to appraise the trend in range condition using grazed transects (GT) and ungrazed transects (UGT). Despite an initial increase, plant cover on the UGT deteriorated in a similar manner to that on the GT. At the conclusion of six years of protection, the cumulative mortality of Indigofera cliffordiana on the UGT exceeded 60 per cent whereas on the GT it was 6 per cent. Furthermore the density of I. cliffordiana on the protected area decreased whereas that on the GT remained substantially unchanged. Aristida mutabilis replaced I. cliffordiana on the UGT but showed little change on the grazed area. Sedera hirsuta disappeared from the GT. On the UGT the percentage of bare ground, despite an initial decline (39.3 ± 7.3 per cent), increased substantially (68.9 ± 15.7 per cent) in parallel with the GT (77.3 ± 4.7 per cent). The results contradict a commonly held view that land degradation only occurs when plants are overused. The findings suggest that degradation can occur in the absence of grazing, especially if the plant species involved are dependent on perturbation. As over‐resting eliminates I. cliffordiana, it seems judicious to allow a 2‐3 year deferral period followed by moderate grazing if it is to be optimally managed.
Impact of protection and free grazing on sand dune vegetation in the Rajasthan Desert, India
Authors: Kumar M. , Bhandari M. M.
Published: February 2007

In the Thar (Rajasthan) Desert of India, sand dunes and sandy plains dominate the landscape. Livestock raising and marginal land cultivation are the main occupations. Owing to the high growth rates of human and livestock populations and a decrease in pasture area and its primary productivity, these lands bear acute grazing pressure. Average rainfall is low and vegetation growth is restricted to the short rainy season of two to four months duration. Often there are years of lower than normal rainfall. In these circumstances, fenced areas, established to stabilize formerly active sand dunes, are increasingly opened to grazing to prevent high stock mortality during droughts. This study was conducted in four fenced and one open site, representative of the region's different vegetation types and grazing pressures. The impact of 2 and 5 per cent free grazing pressure on protected sand dune vegetation density and cover was tested in the two fenced sites. The vegetation data for grazed sites are compared with those for the two ungrazed fenced (protected) and one unfenced (open) site subjected to unlimited grazing pressure throughout the year. The vegetation sampling was carried out by the qaudrat and line‐transect method before and after grazing from November 1984 to October 1986. It shows a significant reduction in the density and cover of many palatable species and an increase of unpalatable plants. The effect of vegetation degradation is greater in the unfenced area. The low grazing pressure on the fenced sand dunes sites can still cause drastic changes in the vegetation density and cover. Protection resulted in reduced sand erosion and enhanced growth of palatable plants in the fenced sites under similar climatic and edaphic conditions to the unfenced sites. The grazing pressure in the unfenced areas remains high to extreme during the year, due to low land productivity and high feed demand. The regeneration rate is very slow under the constant (3rd to 5th degree) overgrazing. Low intensity grazing pressure on the fenced sites during droughts can cause heavy utilization and mortality of palatable vegetation.
Frentes de trabalho: Potentials and limitations of large scale labour employment for soil and water conservation in Cape Verde
Authors: Haagsma B. , Reij C.
Published: February 2007

After gaining independence in 1975 the government of Cape Verde embarked on large scale nationwide employment schemes to carry out soil and water conservation, (SWC) work. Impressive numbers of erosion control schemes have been realized on a scale not seen in other Sahelian countries. the programmes have largely concentrated on mechanical protection and afforestation. Little is known about the impact of these massive SWC activities on agricultural production. Employment has been created by establishing workgangs (frentes de trabalho), which became an important source of income, in particular for the numerous landless peope. These frentes have become institutionalized, and at present their role is increasingly under criticism. Serious problems have arisen with regard to the participation of local land users in the management of natural resources. the consensus now is that local land users should be given greater responsibilities for resource management, supported, where necessary, by the state. However, The role of frentes can be cut back only gradually due to the lack of viable employment alternatives in other sectors of the economy.
Establishment of trees on mixtures of pulverized fuel ASH and Gypsum. I. Tree performance
Authors: Moffat A. J. , Shaw P. J. A.
Published: February 2007

Experiments that investigated the performance of nine tree species planted in pulverized fuel ash (PFA) and gypsum power stattion wastes are described. Lombardy and white poplars, common alder and false acacia were the most successful in gypsum and PFA‐gypsum mixtures, but tree growth in pure PFA was unsatisfactory. Co‐disposal of gypsum and PFA is the best means of promoting the growth of tolerant species planted in power station wastes. Tree performance is improved if these materials are covered by a soil layer, which promotes tree rooting into the underlying wastes.
Modifications of the phosphorus cycle with development of lignite mine soils
Authors: Trasar‐Cepeda M. C. , De Blas E. , Garcia‐Rodeja I. , Leirós M. C. , Gil‐Sotres F.
Published: February 2007

Various aspects of the P cycle in four and seven year old soils from the Meirama lignite mine (northwest Spain) were studied. With increasing soil age, The organic P (Po) content increased in parallel with the organic matter content. the observed increase in secondary inorganic P (Bic—Pi + NaOH‐Pi + us‐NaOH Pi) is related to the increase in the retention capacity for P with soil age. the observed increase in the HCl‐P fraction can be attributed to a gradual dissolution of the non‐extractable forms of P produced from fertilizers added in the course of spoil management. Both the C:Po ratio and phosphatase activity also increased with soil age, suggesting that biochemical mineralization processes are taking place and indicating a need for the hydrolysis of phosphate esters to ensure an adequate phosphorus supply to plants. All these findings suggest that in the long term plants May, suffer a pronounced P deficiency.
Determining the extent and spectral separability of industrially despoiled land in South Wales from satellite sensor data
Authors: Foody G. M. , Cutler M. E.
Published: February 2007

Satellite remote sensing offers the potential to accurately identify and monitor spectrally separable land‐cover classes at a range of spatial and temporal scales. This paper investigates the separability of despoiled land in imagery acquired by sensors carried by the Landsat satellites. These systems offer the opportunity to map areas at large to medium scales at a relatively high temporal frequency and so provide information on environmental quality necessary for many monitoring and planning activities. From an investigation using imagery of South Wales it was found that despoiled land was separable from other classes in the Landsat TM imagery, with an accuracy of over 90 per cent. Furthermore, with Landsat TM data three spectral wavebands were found to provide a level of separability similar to that based on all wavebands available, illustrating potential savings to the analyst. Despoiled land cover was classified from Landsat TM and MSS data and these classifications were evaluated against a manually produced map of despoiled land cover derived from the interpretation of aerial photographs. Estimates of the extent of despoiled land cover in administrative units derived from the Landsat TM data were significantly correlated (r = 0.81) with the map based estimates, although a weaker correlation was observed with Landsat MSS data.
Proposed assessment of the vulnerability of European soils to pollution using a soter shell approach
Authors: Batjes N. H. , Van Engelen V. W. P. , Oldeman L. R.
Published: February 2007

After recent unanticipated occurrences of environmental pollution caused by the time‐delayed and sudden release of contaminants previously believed to be held firmly in soils, awareness has increased that the vulnerability of soils to chemical degradation needs to be assessed and mapped. Although some soils appear to be capable of receiving and holding chemical compounds while at the same time retaining their ecological functions, others are readily damaged. Procedures for identifying areas where vulnerable soils occur are presented, with special reference to the minimum soil data sets that would be required in a small scale study at the European level using geographical information systems. These data can readily be compiled, stored and processed with the relational database management system developed for SOTER, The 1:1 million world soil and terrain digital database project of the International Society of Soil Science, which is co‐ordinated by the International Soil Reference and Information Centre. the proposed initial soil vulnerability programme would essentially serve to increase awareness about areas prone to chemical soil degradation, and will form the basis for implementing soil pollution assessment programmes at larger scales (1:1 M to 1:250 000). the latter national or regional programmes would include the identification of the major sources of soil pollution, and measurement of the accumulated load and the rate of loading according to uniform and standardized procedures, providing the conceptual basis for developing process based models to assess where particular types of soil degradation are likely to occur.
Phosphorus saturation in soils and groundwaters
Authors: Behrendt H. , Boekhold A.
Published: February 2007

On average, crops require about 30 kg ha−1 y−1 of P in humid regions. in some regions fertilizer and manure are applied in amounts that exceed this. the surplus of P in agricultural areas is about 20‐45 kg ha−1 y−1. This implies an accumulation of P. the surplus of P estimated from the balance of agricultural soils of industrialized countries in Europe in the last four decades is between 800 and more than 1500 kg ha−1 although this distribution is not even. Phosphorus accumulation is more than one order of magnitude higher than average in areas with intensive livestock farming. Consequently, The application of high levels of manure exceed the capacity of the soil to store P. This implies that P saturation May, pose a problem. Indeed, about half of the Dutch sandy soils (approximately 300 000 ha) are currently considered to be saturated with P, meaning that there is a hazard of P leaching to groundwaters in the future.

Assuming current phosphate application rates, phosphate leaching is a distinct possibility over a period of decades to a century. Vulnerable areas are soils with high inputs, low sorption capacities for P, high water‐tables and a low retention time for water. the possible consequence is a time‐delayed increase of eutrophication of surface waters (lakes, rivers and the sea) caused by a diffuse load of P in the few next decades. Modelling the influence of different agricultural strategies shows that accumulation of P would not increase further only if the use of P increases by an amount that compensates for the increased inputs. It is proposed to change the current support system of agriculture by installing a system of financial incentives and taxes which seek to promote nutrient balances for each farm.
Effects of stopping liming on abandoned agricultural land
Authors: Hesterberg D.
Published: February 2007

It is suggested that stopping liming on agricultural land could lead to a potential chemical time bomb (CTB). the sequence of interrelated events leading to the CTB include the end of liming, perhaps caused by a change in land use, a progressive decrease in soil pH and increased solubility of potentially toxic contaminants that accumulate in soils as a result of agricultural practices. Data are presented on rates of long‐term soil acidification and modelled changes in the solubility of some trace metals in soil as a result of acidification. Soil acidification rates depend primarily on acid input rates and the soil's acid neutralizing capacity, possibly limited by neutralization kinetics. Experimental data illustrating this point show that the pH decreased rapidly in a field soil receiving ammonium rather than nitrate fertilizer treatment. on a limed agricultural field that was later abandoned and converted to deciduous woodland, The pH of the 0‐23 cm soil layers decreased over 100 years from pH 7 to 4.2. Deeper layers acidified at a slower rate. Thermodynamic model calculations simulating the solubilities of metals in a sandy topsoil showed zinc, cadmium and aluminium solubilities increasing exponentially with decreasing pH, resulting in several‐fold solubility increases between pH 5 and 4. These results suggest how metal solubility increases after liming stops. the model pH‐solubility relationships depended on the type of metal, The solid phase controlling the solubility, and the amount of metal in the soil if adsorption controlled the solubility. Decreasing pH and the resultant increase in metal solubility expected on abandoned farmland might be managed through techniques such as liming or planting forests of selected tree species.
Environmental conditions and chemical time bomb hazards in Poland
Authors: Smal H.
Published: February 2007

Observations on the state of the environment, soil properties, soil hazards and some possible changes in soil parameters are discussed. Sandy and light loamy soils cover more than 50 per cent of the arable land in Poland. About 58 per cent of soils are acid (pH<5‐5) in the surface layer and 25 per cent in the layer from 100 to 150 cm. About 51‐3 per cent of soils are very vulnerable to pollution. According to a BIGLEB‐SOWEP prognosis, in the year 2000 about 13 per cent of soils will be seriously at risk from chemical degradation. Acidification will proceed due to increases in the emission of SO2 and NOx, and the end of liming. the environmental conditions in Poland favour delayed responses to environmental hazards: chemical time bombs.
Chemical time bombs related to forestry practice: Distribution and behaviour of pollutants in forest soils
Authors: Mayer R.
Published: February 2007

Heavy metals and persistent organic pollutants from atmospheric deposition and from fertilizer and pesticide applications are important hazardous substances in forest soils. Data are presented showing that these substances preferentially accumulate in the upper humic horizons of the soils. Another group of substances to be considered in relation to the chemical time bomb concept are the components of humus and soil minerals, mainly nitrogen and metals, which May, be mobilized and thus threaten groundwater quality. Forestry management practices such as thinning, cropping, fertilization and liming are discussed as potential triggers for the mobilization of harmful substances. in this context, The turnover (build‐up and mineralization) of organic matter plays a crucial part. It will be shown, however, that even more danger arises from soil acidification induced by the atmospheric deposition of acidifying pollutants such as sulphates and nitrates.
Riverine and estuarine sedimentation of pollutants and leaks from sludges and wastes: Analytical, prognostic, experimental and remedial approaches
Authors: Förstner U.
Published: February 2007

The effects of chemical time bombs are typically discontinuous and non‐linear. Once a certain threshold has been passed, The system starts to behave differently from before (Stigliani, 1991). a typical example is the consumption of a certain buffer capacity in a system, and the subsequent breakthrough of parameters such as pH values and metal concentrations. the mobilization of metals from different types of waste materials, after the depletion of typical barriers (mechanical or chemical) or after an increase of accelerating factors such as the lowering of pH values, was studied. the release of metals from sediments, leaks of pollutants from sludges and wastes, and some remedial approaches are discussed.
Sediment pollution in the southern baltic
Authors: Lewandowski A. , Szczepanska T.
Published: February 2007

In 1991 geochemical mapping of sediments in the southern Baltic was begun by the Polish Geological Institute, Marine Geology Branch to determine sediment pollution, sediment spreading and the rate of accumulation of pollutants to define ‘hot‐spot’ regions. the initial results on the concentration of heavy metals in 36 samples collected in the Gdansk Basin are presented. One ‘hot‐spot’ is the network of channels in Gdansk Harbour where the bottom sediment (sludge) is highly contaminated. Sampling results and proposals for dredging, separation of the sand fraction, dewatering and the deposition of sludge are discussed.
Sources of heavy metal pollution in the rhine basin
Authors: Rautengarten A.
Published: February 2007

The concept of industrial metabolism is introduced as an analytical framework for many diffuse sources of pollution for which ‘end of pipe’ control will not work and pollution prevention at the source is required. the concept is applied to pollution in the Rhine Basin which ends up in the Netherlands Delta and the North Sea, where the character of the pollutants changes over time. Cadmium, lead and zinc pollution from point sources, traffic, corrosion and atmospheric deposition are considered. Calculations cover the period from 1950 to 2010. in this study strongly urbanized paved and unpaved areas are distinguished based on their transport of pollutants to surface waters.
Low volatile chlorinated hydrocarbons in aquatic sediments in Berlin and surrounding areas
Authors: Terytze K. , Mende W.
Published: February 2007

Low volatile chlorinated hydrocarbons, especially DDT and HCH, have been used as indicators of the level of pollution in aquatic sediments. These compounds were present in all the sediment samples analysed in this study by gas chromatography. Enrichment factors between the water and sediment were high (Kd = 85‐108 for DDT), documenting the strong geoaccumulation of toxic chlorinated hydrocarbons. in contrast with the generally held view, no linear relationship was observed between the concentration of HCH and PCBs and the organic matter content of the sediment. the application of the EVOLON model to determine the kinetics of sorption clearly showed a saturation value. the sorbed amount of low volatile chlorinated hydrocarbons depends to a large extent on the amount of organic matter on the surface of the sediment particles.
Effects of pollution from oil shale mining in Estonia
Authors: Vallner L. , Sepp K.
Published: February 2007

The largest commercially exploited oil shale deposit in the world is in northeast Estonia. the accumulation of solid residues by oil shale mines and processing plants has resulted in numerous dumps and ash hills, which are polluting the environment. the groundwater and streams are highly polluted by sulphates, phenols and oil products. a dump hill of radioactive wastes poses a serious threat to the Baltic Sea. Local people suffer from diseases more often than in other regions of Estonia.
Effects of heavy metals from mining and industry on some rivers in Poland: An already exploded chemical time bomb?
Authors: Suschka J.
Published: February 2007

Upper Silesia has rich deposits of hard coal and substantial deposits of zinc, lead and iron ores. the watersheds of two rivers cut right through the zinc and lead ore mining region and most of the tailing drainage water is contaminated with heavy metals. in total, about 807 tyr‐1 of zinc, 67t yr‐1 of lead and 17 tyr‐1 of cadmium are discharged with the drainage and process waste water. in the Upper Silesia many industrial plants also discharge waste water contaminated with heavy metals. the Bukowno Complex is the most important regional source of heavy metals and the Biala Przemsza River is the main receiver of waste waters from this complex. Measured data at a cross‐section of this river are given. It is shown by a simplified calculation that lead and zinc are transported downstream to the Vistula River and later to the Baltic Sea, or are deposited in the river bed. It is shown that there are many other possible sources of heavy metals. Atmospheric deposition of metals on the surface leads to surface runoff, accumulation in plants, and subsequently discharge with animal or human excreta. Contaminated sediments will continue to pollute the overflowing river water, perhaps for centuries. Mobilization of heavy metals and factors affecting that process are discussed in relation to providing safe drinking water now and in the future. It is emphasized that the drinking water quality is already threatened.
Quaternary aquifer pollution in the notec valley, Poland
Authors: Polanska K.
Published: February 2007

The problem of salinization of ground and surface waters and soils in the Notec valley, Poland is reviewed. the effects of salt mining and the results of a drainage barrier to prevent salt water intrusion in the aquifer and wetlands are considered.
Chemical dump sites in Poland
Authors: Zurek J. , Samsonowicz A. , Gosk E.
Published: February 2007

Recent political and other changes have made it more difficult to manage and control Poland's numerous chemical dump sites. Many previous owners and managers of these sites are no longer in charge and valuable data, collected and stored locally, May, be lost if a countrywide inventory is not made soon. Previously unnoticed surface and groundwater pollution will then increase significantly. Three maps are presented showing the amounts of generated and stored hazardous wastes and the number of chemical dump sites in Poland. Further information is needed on site verification. It is proposed that a computerized database, combining existing and supplementary information, should be developed to provide the decision‐makers with a tool for establishing priorities for monitoring, protective measures and remedial action.
Long‐term environmental risks for soils, groundwaters and sediments in the danube catchment area: The danube chemical time bombs project
Authors: Várallyay G. , Salomons W. , Czíkós I.
Published: February 2007

The accumulation of pollutants in soils, sediments and groundwaters due to natural causes or as a consequence of human activities is a serious problem in the Danube region. the sudden release of the (temporarily) immobilized pollutants as a consequence of various soil degradation processes (acidification, salinization or alkalinization, The destruction of the soil structure and clay minerals, a decrease in the organic matter content and the buffering capacity) is even more harmful. This chemical time bomb phenomena significantly influences the present and future land and water use in the whole Danube catchment area and therefore has great practical significance. the aim of this project, as the first phase of an integrated environmental master plan, is to identify the problems, to delineate problem areas, to analyse the natural system (present status, vulnerability, future risks) and to develop the scientific tools and infrastructure for long‐term environmental risk assessment, which will be the scientific basis for the plan of action to prevent, eliminate or, at least, reduce the harmful side‐effects and the unfavourable ecological and economic consequences of the chemical time bomb in the Danube catchment area.
Effect of vegetation removal on airflow patterns and dune dynamics in the southwest Kalahari desert
Authors: Wiggs G. F. S. , Livingstone I. , Thomas D. S. G. , Bullard J. E.
Published: February 2007

Vegetation is a major control of dune surface activity. To assess the effect of removing vegetation from otherwise largely inactive sand‐dune surfaces, two field experiments were undertaken in the southwest Kalahari Desert of southern Africa. In the first, wind velocity profiles were measured on two flat surfaces, one vegetated and one where vegetation had been removed by fire. In the second, levels of dune surface activity were measured on burnt and vegetated sites over a ten week period. The data indicate a striking increase in the near‐surface wind velocity allied to a decrease in shear stress after the destruction of the vegetation canopy as a result of burning, grazing or drought. Measurements on the consequences of such changes in the airflow patterns on dune dynamics suggest a three‐fold increase in dune surface activity after vegetation clearance. The dunes therefore have a staggered response to the contemporary environment, being largely inactive relicts for much of the time, but becoming more active as vegetation is episodically removed.
Living with the past: Uses of history for understanding landscape change and degradation
Authors: Wasson R. J.
Published: February 2007

The analysis of land degradation is almost always ahistorical, and as a consequence is of diminished value. Global change, as it has come to be known, is thought of as a climatic phenomenon of this and the next century, but has actually been happening as a consequence of land use and climate variation for centuries. Land and water degradation are probably the most obvious manifestations of this global change. The various uses of historical analyses are exemplified in this paper to show their value as contextual explanations, possible analogues of future conditions, a library of experiments already performed, and a narrative of change.
Land‐use change and climate
Authors: Henderson‐Sellers A.
Published: February 2007

Human activities in Australia and world‐wide cause, or contribute to, desertification, deforestation, salinization and soil erosion, and also to reforestation, irrigation and landscape ‘management’. Human‐induced land‐use changes impact on the Earth's climate both locally and on a larger scale, right up to disturbance of the general circulation and hence the global climate. People have become a major environmental agent acting on the future climate through land‐use change, particularly deforestation (and reforestation), desertification (which often includes overgrazing and excessive exploitation of vegetation), agricultural expansion, and soil erosion and degradation. The largest impact of land‐use change on the future climate seems likely to be as a result of enhanced greenhouse gas emissions. At the same time, rapidly increasing populations, especially in the tropics, demand additional food, water for drinking and cleaning, and materials for the construction of shelters—all of which depend upon sustaining a reasonable climate. Climate and human land‐use requirements are linked, but the closeness of that link varies from intimate dependency to callous disdain. In this paper, the impacts of human‐induced land‐use changes on future climate are explored in the context of the projections of global climate models.