Soil Physical Degradation Research Articles

Estimating soil fertility status in physically degraded land using GIS and remote sensing techniques in Chamarajanagar district, Karnataka, India

Soil physical degradation is a major environmental problem throughout the world due to its negative impact on biomass and economic production. This study presented new ways of combining rapid soil analysis using GIS and remote sensing imagery to provide a precision mapping of soil physical condition indicators in the study area and producing fertility status using Geostatistical approach. Study has been carried out to map the areas with physical degradation using remotely sensed data from Indian Remote Sensing LISS III sensor. It was observed that the data enabled better delineation of small units of eroded areas. Satellite data have been used for qualitative assessment of areas, being subject to soil erosion. Soil erosion was found to be none or slight to very sever using visual interpretation of IRS data along with field survey method where soil erosion was found to be moderate to high using the RUSLE method. The eroded areas of degraded lands will be used as an input for planning reclamation and conservation programs in Chamarajanagar district of Karnataka.Soil compaction is a form of physical degradation resulting in densification and distortion of the soil where biological activity, porosity and permeability are reduced, strength is increased and soil structure partly destroyed. Compaction can reduce water infiltration capacity and increase erosion risk by accelerating run-off. The compaction process can be initiated by wheels, tracks, rollers or by the passage of animals. Some soils are naturally compacted, strongly cemented or have a thin topsoil layer on rock subsoil. Soils can vary from being sufficiently strong to resist all likely applied loads to being so weak that they are compacted by even light loads.

Assessment of land degradation and its impact on crop production in the Dry Zone of Myanmar

Land degradation in terms of soil degradation is a major environmental issue posing threat to sustainable livelihood in the semi-arid region of Central Myanmar. However, the studies on soil degradation status and its impacts in this region are very scanty. The objective of this study was to determine the impact of land degradation on crop production both in terms of area and yield in the Dry Zone of Myanmar. Remote sensing and geographic information system-based modelling was utilized to assess and map soil erosion rates. Household survey was conducted to understand the causes of land degradation and its impacts on crop productivity and livelihoods. It has been found out that the current rate of soil erosion ranged from 0 to 114 t ha–1 yr–1, and that the average rate of soil erosion increased from 14.2 to 54.6 t ha–1 yr–1 over a period from 2000 to 2012. The major types of land degradation were physical and chemical soil degradation. Farmers identified topographic condition, soil types, improper crop management practices and climatic factors as the main causes of soil erosion. The observed crop yields of monsoon rice, groundnut, sesame and cotton in the highly degraded area were 3–12 times lower compared with the yields of these crops grown in less degraded area. Livelihoods of the farmers in the high-degraded area were affected by crop yield reduction, increased cultivation cost and increased uncultivable land area. The impact of land degradation on crop production was dependent on the severity of degradation. This suggests that advanced conservation measures are immediately required and the supportive policy strategies need to be implemented to educate farmers and to strengthen extension services for sustainable land management in the Dry Zone of Myanmar.

Calcareous soils in the Northeastern of Brazil: Alterations of attributes from different land use history

The intensive machinery traffic is an important feature of industrial agroecosystems. This traffic when performed under inappropriate moisture conditions can accelerate a series of soil physical properties exchanges, causing deterioration of several soil quality indicators. Intensive agricultural activity is advancing rapidly in western Sergipe State and northeastern Bahia State (Brazilian semi-arid regions), mainly on soils developed from limestone substrata. This study characterized the soils and investigated the effect of increasing periods of corn crops and other land use types on soil attributes of calcareous soils from Western Sergipe State, with emphasis on physical attributes, particulate organic matter, and total organic C. Five combinations with five replicates of land use were selected: dry forest (DF); corn crop (first, fourth and tenth year - C1, C4 and C10) after forest removal; and intensive pasture (IP). The study areas were dominated by soils with vertic properties. Almost all the chemical and physical attributes showed a lesser quality in IP sites compared with the other treatments. The differences among the DF sites and corn crop sites were smaller. When compared the land use time of corn crop treatments (with DF as zero time), tenuously, some attributes formed two groups, where DF and C1 treatments were separated from C4 and C10 treatments. Regarding the comparison of all treatments, the non-metric multidimensional scaling technique explained 94% of the variability (in two axis) of the 19 attributes analyzed, being the major part represented by axis 1 (79%). The IP sites had the greatest soil physical degradation index among all groups. The C1 sites had significant contrast compared with the DF sites. The C4 sites showed a loss of quality in many soil physical properties compared with C1 sites. There were no differences between the C4 and C10 sites. This shows that in order to achieve a near steady state a greater number of cultivation years is required.

Influence of wildfire severity on soil physical degradation in two pine forest stands of NW Spain

This study examined the effect of wildfire on the physical degradation of two forest soils in NW Spain and compared this against changes produced by controlled laboratory heating experiments in which unburned soils from neighbouring sites were exposed to five different heating regimes. The physical soil degradation was considered with respect to organic carbon content, dry aggregate size distribution, water aggregate stability, water repellency, and hydraulic conductivity. The results of this analysis show that the changes in the physical properties of the wildfire-affected soils were similar to the changes observed in the heating experiments. However, the wildfire had contrasting effects in terms of soil physical degradation at the two study sites, which can be attributed to differences in soil heating regimes and fire severity. At one study site, the wildfire did not produce marked changes in organic carbon content or in aggregation, except for a slight fragmentation of macro-aggregates into micro-aggregates. Also, soil water repellency remained very strong after the wildfire, resulting in low hydraulic conductivity. Based on the laboratory experiments, the soil at this site was not exposed to temperatures above 220°C. The wildfire at the other study site resulted in more pronounced degradation of the soil, as shown in the reduction of organic carbon content by almost 50%, resulting in reduced stability of the aggregates. The wildfire also reduced soil water repellency considerably, but hydraulic conductivity did not increase noticeably. In this case the soil could be exposed to temperatures between 220 and 380°C.

Elements of Climate Evolution in yhe Area Between Prut and Dniester Rivers. Landscape and Pedogenetic Implications

Abstract Component part of the Carpathian-Danubian-Pontic space, the interfluve area between Prut and Dniester is subject to the regional process of climate evolution and change. In what regards the concept of human-influenced pedogenesis, the role of the biological factor is significantly reduced. As a consequence the direction and intensity of the elementary landscape and pedogenetic processes are determined by the relations between climate and the geomorphological factor. In the conditions of a relative stability of the geomorphological factor, the determining role is held by climate. To this is added soil vulnerability to the implications of climate changes, determined by the degree of soil physical degradation but also by a series of intrinsic and external (drainage) factors. This implies the idea of the control and management of the landscape and pedogenetic implications of climate changes by improving soil physical characteristics.

Unravelling landslide risk: soil susceptibility, agro‐forest systems and the socio‐economic profile of rural communities in Italy

AbstractLandslides are considered a form of physical soil degradation and are concentrated, especially in southern European countries, on inland and marginal rural areas. Low‐density, economically disadvantaged and poorly accessible areas are assumed to share a high landslide occurrence probability. However, an empirical verification of this assumption is still lacking for Mediterranean countries. This study investigates the spatial relation between a composite index of landslide risk and more than 100 indicators at the municipal level in Italy – a country with high landslide risk – exploring multiple territorial dimensions (population dynamics and settlements, job market and human capital, economic specialization and competitiveness, quality of life, agriculture and rural development, territory and environment). We combine nonparametric correlation, principal component analysis and hierarchical clustering, to profile municipalities according to their levels of landslide risk. The high landslide risk in certain areas of Italy is related to specific socio‐economic attributes (depopulation, ageing, tourism specialization, low density of economic activities, modest participation to the job market and crime intensity) and agro‐environmental features (low‐intensity cropping systems, natural landscapes and water resource availability).

Measuring soil compaction and soil behavior under the tractor tire using strain transducer

Soil compaction can occur due to machine traffic and is an indicator of soil physical structure degradation. For this study 3 strain transducers with a maximum displacement of 5cm were used to measure soil compaction under the rear tire of MF285 tractor. In first series of experiments, the effect of tractor traffic was investigated using displacement transducers and cylindrical cores. For the second series, only strain transducers were used to evaluate the effect of moisture levels of 11%, 16% and 22%, tractor velocities of 1, 3 and 5km/h, and three depths of 20, 30 and 40cm on soil compaction, and soil behavior during the compaction process was investigated. Results showed that no significant difference was found between the two methods of measuring the bulk density. The three main factors were significant on soil compaction at a probability level of 1%. The mutual binary effect of moisture and depth was significant at 1%, and the interaction of moisture, velocity, and depth were significant at 5%. The soil was compressed in the vertical direction and elongated in the lateral direction. In the longitudinal direction, the soil was initially compressed by the approaching tractor, then elongated, and ultimately compressed again.

Assessment of potential soil degradation on agricultural land in the czech republic.

Many attempts have been made worldwide to develop methods to identify the areas most threatened by soil degradation. Some soils in afflicted areas may be irreversibly degraded and thus have very little resilience (the ability to restore themselves). For the purpose of assessing the current state of soil degradation in the Czech Republic (CZ) we have developed an overall indicator of land vulnerability to the threat of soil degradation on the basis of individual factors that contribute to soil degradation and are monitored on a long-term basis in various research worksites in the CZ. Individual degradation factors were divided into two groups: chemical and physical degradation. On the basis of principal component analysis, individual degradation factors were assigned a specific weight of influence. With the use of a GIS, the input factors of degradation were combined to create maps of chemical and physical soil degradation, and consequently a map of overall degradation-threatened soils for the CZ, along with a map of areas differentiated according to the prevailing type of degradation. Results showed that, at present, the most important degradation factor in the CZ is water erosion, followed by loss of organic matter. Statistical analysis showed that approximately 51% of agricultural land is moderately threatened in the CZ.

Soil Degradation and Soil Quality in Western Europe: Current Situation and Future Perspectives

The extent and causes of chemical, physical and biological degradation of soil, and of soil loss, vary greatly in different countries in Western Europe. The objective of this review paper is to examine these issues and also strategies for soil protection and future perspectives for soil quality evaluation, in light of present legislation aimed at soil protection. Agriculture and forestry are the main causes of many of the above problems, especially physical degradation, erosion and organic matter loss. Land take and soil sealing have increased in recent decades, further enhancing the problems. In agricultural land, conservation farming, organic farming and other soil-friendly practices have been seen to have site-specific effects, depending on the soil characteristics and the particular types of land use and land users. No single soil management strategy is suitable for all regions, soil types and soil uses. Except for soil contamination, specific legislation for soil protection is lacking in Western Europe. The Thematic Strategy for Soil Protection in the European Union has produced valuable information and has encouraged the development of networks and databases. However, soil degradation is addressed only indirectly in environmental policies and through the Common Agricultural Policy of the European Union, which promotes farming practices that support soil conservation. Despite these efforts, there remains a need for soil monitoring networks and decision-support systems aimed at optimization of soil quality in the region. The pressure on European soils will continue in the future, and a clearly defined regulatory framework is needed.

Escarificação e adubação orgânica: efeito na recuperação estrutural de solo produzindo Tifton 85

A produção intensiva de forrageiras para fenação aumenta os riscos de degradação física do solo e a escarificação, associada ou não com a adubação orgânica, pode ser alternativa para a recuperação estrutural desses solos. Assim, objetivou-se avaliar os efeitos da escarificação do solo, da adubação orgânica e adubação mineral, na densidade e porosidade do solo e na produtividade da Tifton 85. O experimento foi conduzido em uma área cultivada por dez anos para feno com Tifton 85. Apenas a escarificação promoveu alterações significativas nos atributos físicos do solo, principalmente na profundidade de 0,03-0,08m, mantendo-se por pelo menos nove meses. O curto período entre a escarificação e o primeiro corte para fenação prejudicou a produtividade da Tifton 85, porém não houve diferença na produtividade acumulada entre os manejos do solo ao fim de uma estação de crescimento da pastagem. A produtividade foi maior para os tratamentos com reaplicação de nitrogênio mineral em relação à testemunha, sendo que a produtividade com o uso de cama de aves foi inferior à adubação mineral no somatório dos quatro cortes da gramínea

Atributos físicos de Cambissolo Háplico em vinhedos submetidos a intensidades de tráfego

Em vinhedos, o tráfego de máquinas agrícolas causa compactação do solo que pode ser mais acentuada nas entrelinhas pela maior intensidade de tráfego. Este trabalho objetivou avaliar a variabilidade dos atributos físicos do solo em razão da posição de amostragem em relação à linha de plantio, em vinhedos comerciais da variedade Bordô em pé franco, submetidos a diferentes manejos da cultura. Em fevereiro de 2012, três vinhedos foram selecionados no município de Major Gercino (SC), sendo um manejado sem a utilização de máquinas agrícolas (vinhedo 1: com seis anos de implantação) e dois que utilizam máquinas nas entrelinhas (vinhedos 2 e 3: com oito e 17 anos, respectivamente). Na linha de plantio (Lp), na linha do rodado (Lr) e entre a linha de plantio e a linha do rodado (El), foram coletadas amostras indeformadas de solo nas camadas de 0,00-0,05, 0,05-0,10, 0,10-0,15 e 0,15-0,20 m de profundidade. Avaliaram-se a densidade do solo (Ds), a resistência à penetração (Rp), as classes de poros (macroporos - MaP, mesoporos - MeP, microporos - MiP e porosidade total - PT), os índices de agregação e de estabilidade de agregados (Diâmetro médio geométrico dos agregados secos ao ar e estáveis em água - DMGsa e DMGea, índice de estabilidade de agregados - IEA), a umidade gravimétrica (Ug), a densidade das partículas e a granulometria do solo. O estado de compactação aumentou no sentido da Lp para a Lr. A ocorrência de tráfego, em geral, influenciou negativamente os atributos avaliados. Entre as posições de amostragem, os maiores valores de Ds e Rp ocorreram na Lr, em que a Rp atingiu valores críticos ao desenvolvimento de raízes; nos vinhedos mecanizados, foram encontrados elevados valores de Rp e baixos de MaP nas camadas de 0,00-0,05 e 0,05-0,10 m. Observaram-se agregados com maior diâmetro e menores IEA, o que indica deterioração da qualidade física do solo. No vinhedo 1, houve menor variabilidade dos atributos físicos, enquanto no vinhedo 2 verificou-se influência negativa do tráfego de máquinas, principalmente para os atributos relacionados à agregação e elevada MiP. No vinhedo 3, observaram-se os maiores índices de Rp e de Ds, bem como o menor valor de MaP. Portanto, em relação aos vinhedos estudados, verificou-se aumento da degradação física do solo proporcionado pelo tráfego de máquinas (vinhedos 2 e 3). Dentre as posições de coletas e os vinhedos, evidenciou-se, por meio da análise de componentes principais, a separação da posição Lr do vinhedo 3, em razão dos atributos Ds e Rp, permitindo inferir que o manejo adotado na posição Lr está ocasionando maior degradação da qualidade física do solo.

Ecological Factors Influencing Physical Soil Degradation in the Atacora Mountain Chain in Benin, West Africa

This study analyzed the ecological factors influencing soil degradation in the Atacora Mountains in northern Benin, which harbor two endemic species, Thunbergia atacorensis and Ipomoea beninensis. Data were collected along line transects from plain to summit within 22 plots of 30 m × 30 m. Indicators of physical soil degradation (extent of organic layer, color of topsoil, compactness of soil, presence and extent of rills, and occurrence of sheet erosion) and environmental factors (canopy and ground cover, topography, occurrence of flooding, and slope) were assessed. Cluster analysis identified 4 soil degradation classes: light, moderate, high, and extreme. Discriminant and multivariate variance analyses identified canopy and ground cover as the 2 main ecological drivers of soil degradation. Plant, litter, and stone cover were found to decrease as soil degradation increased. The parts of the Atacora Mountains with high elevation and steep slope were found to be less degraded than areas with low slopes, which are easily accessible for human activities. Policies to mitigate soil degradation should prioritize practices with low impact on vegetation cover and promote soil protection practices such as tree planting and mulching.

Constraints for the restoration of tropical alpine vegetation on degraded slopes of the Venezuelan Andes

Background: In the Venezuelan high Andes, wheat cultivation on steep slopes since colonial times has caused the degradation of extensive areas. After several decades of abandonment, natural succession has not allowed the spontaneous recovery of the original alpine vegetation.Aims: Our aim was to identify a degradation gradient, based on vegetation structure, and relate this gradient to different environmental factors (grazing intensity, physical soil degradation, distance to seed sources and loss of soil fertility) that could be preventing spontaneous succession.Methods: Vegetation structure and 22 environmental variables were sampled on 92 slopes with different degrees of degradation. Multivariate statistics were used to relate the state of the vegetation to environmental factors.Results: Six types of vegetation were identified and ranked along a degradation gradient. Several soil properties, for example C, N, clay content and cation-exchange capacity, decreased by as much as 50% along this gradient, while other variables, such as current grazing intensity were only slightly correlated to the degradation gradient.Conclusions: Vegetation and soil properties were clearly related to a strong degradation gradient, caused by former wheat cultivation and overgrazing, with symptoms of desertification. Restoration practices have to be directed towards re-establishing soil organic matter and its functional role in regulating water balance and nutrient cycling.

Efeito de semeadora com haste sulcadora para ação profunda em solo manejado com plantio direto

A adoção do plantio direto na região subtropical úmida do Brasil, fundamentada apenas em dois preceitos da agricultura conservacionista - mobilização de solo restrita à linha de semeadura e manutenção de resíduos culturais na superfície do solo -, tem induzido à estratificação de atributos químicos do solo na camada de 0-20 cm profundidade e degradação física da camada subsuperficial (entre aproximadamente 5-20 cm de profundidade), que podem contribuir para frustrações de safras agrícolas, quando da ocorrência de estiagens. O objetivo deste trabalho foi avaliar o efeito residual de uma semeadora/adubadora, equipada com elemento rompedor de solo tipo haste sulcadora, atuando em quatro profundidades para a semeadura de milho (Zea mays L.), na mitigação de problemas de ordem física e química, em um Latossolo Vermelho distrófico húmico, manejado em plantio direto há mais de 10 anos. Os tratamentos avaliados foram: T1 = hastes sulcadoras atuando até 5 cm de profundidade; T2 = hastes sulcadoras atuando até 10 cm de profundidade; T3 = hastes sulcadoras atuando até 15 cm de profundidade; e T4 = hastes sulcadoras atuando até 17 cm de profundidade. O efeito desses tratamentos sobre os atributos físicos do solo foi avaliado pela técnica do perfil cultural associada à determinação da densidade, porosidade total, macroporosidade e resistência do solo à penetração, aos oito e 12 meses, após a semeadura da cultura de milho. Sobre os atributos químicos, esses efeitos foram avaliados pela determinação de pH em H2O, P e K disponíveis, Ca, Mg e Al trocáveis, acidez potencial e matéria orgânica, em amostras de solo coletadas em camadas de 2,5 cm de espessura, de 0-22,5 cm de profundidade. A utilização da semeadora/adubadora, equipada com elemento rompedor de solo tipo haste sulcadora, evidenciou-se eficaz em mitigar os problemas físicos e químicos do solo, tanto aos oito como aos 12 meses após a operação de semeadura.

Atributos físico-hídricos de um Argissolo amarelo sob floresta e savana naturais convertidas para pastagem em Roraima

O Estado de Roraima apresenta ampla diversidade pedológica e de ecossistemas, sendo gradativamente ocupados com pastagem, que dependendo do manejo podem estar associadas à degradação física do solo. Dentro desse contexto, este trabalho foi realizado com os objetivos de avaliar e comparar os atributos físico-hídricos de um Argissolo Amarelo sob os ecossistemas de savana e floresta natural, convertidos em pastagem para pecuária. Os tratamentos principais foram savana natural (SN), savana convertida em pastagem (SC), floresta natural (FN) e floresta convertida em pastagem (FC) e os tratamentos secundários foram as profundidades de amostragem do solo, 0-10, 10-20 e 20-40 cm. Os atributos avaliados foram: granulometria, densidade do solo (DS) e de partículas (DP), resistência à penetração (RP), porosidade total (PT), umidade gravimétrica (UG), capacidade de armazenamento de água (CAD) e matéria orgânica do solo (MOS). A DS foi superior nas duas áreas de Savana, não havendo diferença entre SC e SN em nenhuma das profundidades. A RP variou em função das áreas e da profundidade, verificando-se influência da conversão nesse atributo. A PT foi maior na FN e menor na SC; houve diminuição da porosidade com a profundidade. A CAD foi maior na FN apenas na profundidade de 0-10 cm. A MOS foi superior nas áreas de FN e FC. Portanto, a conversão dos ambientes naturais em pastagem provocou alterações significativas na RP, DS, CAD, PT e MOS, com maior expressividade nas áreas da FC em razão da supressão da cobertura vegetal natural, que tem na matéria orgânica o condicionador da qualidade físico-hídrica do solo. Na SC, por sua vez, a supressão da cobertura vegetal natural não provocou a mesma expressividade por causa dos teores significativamente inferiores de MOS.

Деградаційні процеси у дерново-підзолистих ґрунтах Надсянської рівнини

The study results of physical features of sod-podzolic soils at Nadsiannia moraineoutwash plain have been outlined. There has been given the description of levels of soil physical degradation under different lands based on the content of agronomically valuable aggregates, structure density and total porosity. The solutions to improve some properties of degraded soils have been proposed. Key words: degradation, agronomically valuable aggregate, structure density, total porosity.

Intervalo hídrico ótimo para avaliação da degradação física do solo

A influência do sistema de uso e manejo na qualidade física do solo tem sido tema de destaque em razão de seus impactos ambientais e agronômicos. O intervalo hídrico ótimo (IHO) é um moderno indicador da qualidade física que potencialmente pode apresentar os mecanismos e processos de perda ou recuperação da qualidade física do solo, por causa do seu uso e manejo. Diante disso, o objetivo deste trabalho foi quantificar a influência de diferentes sistemas de uso e manejo no IHO de um Latossolo Vermelho distrófico, textura franco-arenosa, composto por 170, 40 e 790 g kg-1 de argila, silte e areia, respectivamente. Foram selecionadas quatro áreas, sob os seguintes sistemas de uso e manejo do solo: mata nativa; pastagem cultivada por mais de 20 anos; citros por mais de 10 anos, antecedido por 10 anos de pastagens; e cultivo com culturas comerciais (milho, sorgo, aveia e mandioca), por cerca de 15 anos, após 10 anos de pastagem cultivada. Foram coletadas 48 amostras indeformadas, em cada área, no centro da camada de 0-0,10 m de profundidade. As amostras foram submetidas a potenciais de -10 a -15.000 hPa, em que foram determinadas a curva de retenção de água, a curva de resistência do solo à penetração e, posteriormente, a densidade do solo (Ds) e o IHO. A Ds foi influenciada pelos sistemas de uso e manejo do solo na sequência cultivo = citros > pastagem > mata nativa. A relação entre IHO e Ds foi linear e negativa, à exceção da mata nativa que na faixa de Ds entre 1,35-1,55 Mg m-3 apresentou relação positiva. Valores de Ds, em que o IHO = 0, associados com severa degradação física do solo, foram de 1,75 e 1,80 Mg m-3, nos solos sob citros e cultivo, respectivamente; a proporção desses valores foi de 21 % para o solo sob citros e 18 %, para o sob cultivo. A perda de qualidade física do solo foi menos acentuada no solo sob pastagem, quando comparado com os solos sob citros e cultivo, sendo a diminuição do IHO menos acentuada com o aumento da Ds. O menor valor de Ds em que iniciou a redução do IHO foi tomado como densidade do solo de alerta (Ds a). A Ds a foi de 1,55 Mg m-3 e pode ser utilizada como valor de referência no processo de recuperação da qualidade física do solo, válida para solos com textura, uso e manejo semelhante ao deste estudo.

Agrophysics - physics in agriculture and environment

Abstract Agrophysics is one of the branches of natural sciences dealing with the application of physics in agriculture and environment. It plays an important role in the limitation of hazards to agricultural objects (soils, plants, agricultural products and foods) and to the environment. Soil physical degradation, gas production in soils and emission to the atmosphere, physical properties of plant materials influencing their technological and nutritional values and crop losses are examples of such hazards. Agrophysical knowledge can be helpful in evaluating and improving the quality of soils and agricultural products as well as the technological processes.

Role of sweetclover and phacelia in agriculture ecology improvement for droughty left-bank areas of Saratov region

Ecological pollution and physical degradation of soil depend strongly on anthropogenic action on it. The role of such legumes as biennial yellow sweetclover, annual white sweetclover, and plants of Boraginaceae family—lacy phacelia and blue curls—in improvement of physical and chemical soil properties was investigated. An ecologically safe way for soil fertility increase under droughty conditions is offered. Use of both species of sweetclover and one species of phacelia tanacetifolia as green manure in crop rotations are recommended.

Soil Chemical Aspects of Water Management: Modeling Topsoil Water, Salt and Sodicity Dynamics

In large areas worldwide, both in semi-arid and humid climates, the availability of good quality water for primary production in agriculture or natural vegetations is limited. Whereas soil and groundwater pollution are nowadays general problems, much larger areas have to deal with the hazards of soil and groundwater salinity. For soil types that are susceptible to physical degradation in view of their swelling and shrinking behaviour, also the salinity associated hazard of soil sodicity needs to be anticipated. Sodicity related soil physical degradation may be quite irreversible and is a major candidate for preventive rather than curative measures. The process of salt displacement has received much attention, and spatial variability has been given explicit attention by Dagan and Bresler (1979). Temporal variability of the boundary conditions has been investigated only recently, when both primary and secondary salinity were studied with so-called minimalist ecohydrological modelling (Suweis et al., 2010, Shah et al., 2011, Vervoort and Van der Zee, 2012). This work emphasized the atmospheric forcing of erratic rainfall on water and salt dynamics in the rootzone layer, either envisioned as a Poisson process, or with seasonal periodicity. Taking such erratic rainfall as well as spatial variability of the depth of the groundwater level into account, an impression can be obtained of the importance of different sources of variability. For our parameterization, we find that both spatial and temporal variability were responsible for the variation in root zone salinity, C, but that root zone sodicity, expressed with the Exchangeable Sodium Percentage, ESP, depends predominantly on spatial variability. The difference is understandable from the buffering mechanisms involved with C and ESP.