Soil Salinization Processes Research Articles

Evaluation of the Impact of Different Soil Salinization Processes on Organic and Mineral Soils

Soil salinization is a worldwide problem of which secondary salinization is increasingly more frequent, threatening agricultural production. Salt accumulation affects not only plants but also the physio-chemical characteristics of the soil, limiting its potential use. Climate change will further increase the rate of salinization of soil and groundwater as it leads to increased evaporation, promotes capillary rise of saline groundwater as well as increased irrigation with brackish water. Episodic seawater inundation of coastal areas is likely to increase in frequency as well. This work analyzed three types of salinization: seawater inundation (by irrigating soils with a 54 dS m−1 NaCl solution), saline groundwater capillary rise (soil contact with a 27 dS m−1 NaCl solution), and irrigation with two types of brackish water with different residual sodium carbonate (RSC). Two soils were used: a mineral soil (7.0 % clay; 0.7 % organic matter) and an organic soil (2.7 % clay; 7.4 % organic matter). The tested soils had different resilience to salinization: The mineral soil had higher sodium adsorption ratio (SAR) due to low levels of calcium + magnesium but had higher leaching efficiency and more limited effects of RSC. The organic soil however was more prone to capillary rise but seemingly more structurally stable. Our results suggest that short-term inundation with seawater can be mitigated by leaching although soil structure may be affected and that capillary rise of brackish groundwater should be carefully monitored. Also, the impact of irrigation with brackish water with high RSC can be inferior in soils with higher exchangeable acidity.

Managing soil salinity with permanent bed planting in irrigated production systems in Central Asia

Land degradation due to water logging and its influence on secondary soil salinization processes pose a major threat to the sustainability of irrigated agriculture in the semi-arid production ecologies of Central Asia. In rainfed conditions, conservation agriculture (CA) practices, i.e., reduced tillage, residue retention and crop rotation, have proven to have substantial scope for arresting or reversing soil degradation. Previous research findings suggest that CA can be beneficially applied to irrigated croplands as well, but influences on salinization processes are insufficiently documented. This study investigates the effect of CA practices on soil salinity dynamics in irrigated production systems in the Khorezm region, Uzbekistan, Central Asia. The study was conducted under a cotton-wheat-maize rotation system, typical for the region, from 2007 to 2009 with two tillage methods (‘CA’ – permanent raised beds (PB); conventional tillage (CT)) combined with two residue levels (residue harvested (RH); residue retained (RR)). Compared to pre-experiment levels, salinity in the top 30cm soil increased significantly during cotton (May–October), while a negligible change occurred during wheat (October–June) and maize (July–September) season. In absence of crop residues, soil salinity on top of the beds increased compared to CT without crop residue retention. When retaining crop residues, the soil salinity under PB was reduced by 32% in the top 10cm and by 22% over the top 90cm soil profile compared to CT without crop residue retention. Thus, PB+RR seems a promising option to slow down on-going soil salinization in salt-affected agro-ecologies such as those in the irrigated arid lands of Central Asia.

MODFLOW Modeling to Solve Drainage Problems in the Argaman Date Palm Orchard, Jordan Valley, Israel

Overwetting and soil salinization processes are common in irrigated date palm orchards in Israel. Subsurface drainage systems are generally used to overcome soil salinity. Subsurface drainage models can contribute to the selection of a proper drainage system and its proper placement in the field. In this paper, the groundwater flow modeling program MODFLOW was used to simulate groundwater levels in a date palm orchard in Argaman, in the Jordan Valley, Israel. Using a three-layer groundwater flow model, the most efficient drainage system was a combination of 4.5-m depth primary drains and 3-m depth drains of different lengths installed at a different spacing between drains. Installation of this drainage system would cost approximately NIS$2.6 million, i.e., 30% less than the initially proposed project. Given certain input, a spatially distributed groundwater flow model such as MODFLOW can provide more reliable information than different analytical solutions for planning an effective subsurface drainage system.

Satellite-based monitoring of decadal soil salinization and climate effects in a semi-arid region of China

Soil salinization is a common phenomenon that affects both the environment and the socio-economy in arid and semi-arid regions; it is also an important aspect of land cover change. In this study, we integrated multi-sensor remote sensing data with a field survey to analyze processes of soil salinization in a semi-arid area in China from 1979 to 2009. Generally, the area of salt-affected soils increased by 0.28% per year with remarkable acceleration from 1999 to 2009 (0.42% increase per year). In contrast, the area of surface water bodies showed a decreasing trend (−0.08% per year) in the same period. Decreases in precipitation and increases in aridity due to annual (especially summer) warming provided a favorable condition for soil salinization. The relatively flat terrain favored waterlogging at the surface, and continuous drought facilitated upward movement of soil water and accumulation of surface saline and calcium. Meanwhile, land-use practices also played a crucial role in accelerating soil salinization. The conversion to cropland from natural vegetation greatly increased the demand for groundwater irrigation and aggravated the process of soil salinization. Furthermore, there are potential feedbacks of soil salinization to regional climate. The salinization of soils can limit the efficiency of plant water use as well as photosynthesis; therefore, it reduces the amount of carbon sequestrated by terrestrial ecosystem. Soil salinization also reduces the absorbed solar radiation by increasing land surface albedo. Such conversions of land cover significantly change the energy and water balance between land and atmosphere.

Spatial Variation of Soil Salinity in the Mexicali Valley, Mexico: Application of a Practical Method for Agricultural Monitoring

The degradation of irrigated lands through the process of soil salinization, or the buildup of salts in the soil, has hampered recent increases in agricultural productivity and threatens the sustainability of large-scale cultivation in critical agricultural regions of the world. Rapid detection of soil salinity on a regional basis has been identified as key for effective mitigation of such land degradation. The ability to detect regional patterns of soil salinity at an accuracy sufficient for regional-scale resource management is demonstrated using Landsat 5 Thematic Mapper (TM) imagery. A case study of the Mexicali Valley of Baja California, Mexico was selected due to the region's agricultural significance and concern for future soil salinity increases. Surface soil salinity was mapped using georeferenced field measurements of electrical conductivity (EC), collected concurrently with Landsat 5 TM imagery. Correlations between EC measurements and common indices derived from the satellite imagery were used to produce a model of soil salinity through regression analysis. Landsat band 7, TNDVI, PCA 1, Tasseled Cap 3 and Tasseled Cap 5 were found to offer the most promising correlations with surface soil salinity. Generally low levels of soil salinity were detected, however, distinct areas of elevated surface salinity were detected at levels potentially impacting sensitive crops cultivated within the region. The difficulty detecting low levels of salinity and the mid-range spatial resolution of Landsat 5 TM imagery restrict the applicability of this methodology to the study of broad regional patterns of degradation most appropriate for use by regional resource managers.

Assessing soil salinity hazard in cultivated areas using MODFLOW model and GIS tools: A case study from the Jezre’el Valley, Israel

A high water table and soil salinization processes are common in irrigated fields in the Jezre’el Valley of Israel. This valley, located in the Lower Galilee in the northern part of the country, covers nearly 300km2. In general, salinization is accelerated when a field is underlain by a shallow, semi-confined aquifer exerting upward hydraulic pressure, which impedes drainage of the overlying soil layers. Owing to its hydrological setting, the Jezre’el Valley has inherent drainage problems, which were aggravated in the 1960s by the introduction of intensive irrigated farming. The water table rose, leading to soil salinization problems. By 1989, 1500ha showed soil salinity problems and by 1991, an area of 3300ha was affected by salinity. In this study, the MODFLOW groundwater flow model was used to simulate groundwater levels in the Jezre’el Valley. Geo-database and ArcGIS techniques were used for model input of the required dates, spatial analysis of the model results, and assessment of areas under soil salinity hazard, based on two hydrogeological criteria: (1) groundwater table depth from the soil surface and (2) difference between groundwater levels in the upper soil layer and semi-confined aquifer. It was found that the total area with intensive soil salinization is 325ha, and that with potential soil salinization 6275ha. With the appropriate input, a spatially distributed groundwater flow model such as MODFLOW can provide reliable information for the planning of an effective subsurface drainage system to prevent soil salinization.

Application of chemometrics to spectroscopic data for indicating humification degree and assessing salinization processes of soils

Purpose Chemometric methods were used to analyze chemical/spectroscopic data of fulvic acid (FA) isolated from soils in Hetao Irrigation District of China and to indicate humification degree of soil organic matter and assess soil salinization processes.

Fluorescence Spectroscopic Properties of Dissolved Fulvic Acids from Salined Flavo‐aquic Soils around Wuliangsuhai in Hetao Irrigation District, China

This study was conducted to discuss fluorescence spectroscopic properties of dissolved fulvic acids (FA) isolated from salined flavo‐aquic soils around Wuliangsuhai Lake in Hetao Irrigation District, and to evaluate humification degree of FA and soil salinization processes. Composite soil samples of different depths (0–20, 20–40, 40–60, and 60–80 cm) were collected from four different halophyte communities along a saline‐impact gradient around Wuliangsuhai Lake, namely, Comm. (Community) Salicornia europaea (CSE), Comm. Suaeda glauca (CSG), Comm. Kalidium foliatum (CKF), and Comm. Sophora alopecuroides (CSA). Ten humification indices (HIX) (A4/A1, A465, I383/I330, I460/I355, I460/I380, S355–460, S380–460, AF3/AF1, AF3/AF2, and r), deduced from fluorescence spectra of FA, were used to assessing humification degree. Aromatic C structure of FA was the most complex in the CSA soils, and humificaiton degree was the highest too, followed by CKF, CSG, and CSA. There were significant relationships among the 10 HIX (P < 0.01), and A465, S355–460, and S380–460 can more indistinctly differentiate humification degree than the other seven HIX. The 10 HIX exhibited good correlations with exchangeable sodium percentage (ESP), and humification degree rose with the decreasing ESP. The HIX not only indicate humification degree, but character soil salinization processes. Therefore HIX may be used as a surrogate for ESP, and may be indicative of soil salinization processes. This study can provide a theoretical basis for the prevention of desertification and saline soil remediation.

Saline waters and soil quality

The processes of secondary salinization due to anthropic actions are considered one of the most important environmental emergencies owing to their level of dangerousness. The soils of the dry areas of the Mediterranean basin are particularly prone to these processes. In such environments, it is imperative to resort to irrigation that allow for the reduction of risks due to soil moisture deficit and for the stabilization of yields. Frequently, saline waters are used that cause a lowering of the soil quality. If on one hand the presence of salts can benefit the soils mainly improving soil structure, on the other high levels of salts produce negative effects on soils and crops.When sodium prevails problems of soil quality can rise such as structure degradation, low hydraulic conductivity, soil sealing. The processes of secondary soil salinization due to the use of saline waters for irrigation are particularly evident in our Country among others. In Italy, saline soils are mainly distributed in long strips of the coastal belt of the Tyrrhenian sea and Adriatic sea, in the coastal belt of Apulia, Basilicata and Sardinia and in wide areas of Sicily. It is not possible to suggest general actions to combat soil salinization because we must take into consideration that in the relationship soil-water two different quality concept interact: one linked to the soils, the other to the waters.

Applying MODFLOW Model for Drainage Problem Solution: A Case Study from Jahir Irrigated Fields, Israel

High water table and soil salinization processes are common in irrigated fields in Israel. Subsurface drainage systems are a common technique to solve soil salinity problems. Subsurface drainage models can contribute to the efficiency of the drainage system as it can assist in the selection of the proper drainage system and its proper placement in the field. In this study we used the MODFLOW groundwater flow model to simulate groundwater levels in Jahir irrigated fields, the Jordan Valley, Israel. Using a three-layer groundwater flow model, the most efficient drainage system was found to be a combination of deep drains with relief wells and a pump placed in the area with soil salinity problem and upward hydraulic pressure. It was found that simulated drainage system can yield nearly 200,000m3 of water per year. Given certain information, a spatially distributed groundwater flow model such as MODFLOW can provide more reliable information than different analytical solutions for planning of an effective subsurface drainage system.

Potential risk of soil salinization in different regions of Central Asia with special reference to salt reserves in deep layers of soils

To analyze the potential risk of secondary soil salinization along with the development of irrigation agriculture, an extensive soil survey was conducted with special reference to the salt concentration in deeper layers of soils in different regions of Central Asia (Kazakhstan and Uzbekistan). In total, 41 soil profiles from different scales of distance, that is, from within respective farms to over different countries, were analyzed for soluble salt contents and particle size distribution. A regional trend was found in terms of the contents of soluble salts in the 100–200 cm layers of soils, which is considered to represent a potential risk of secondary soil salinization. The detailed findings were as follows. In the Ili watershed, the contents of soluble cations tended to be low. In the Fergana regions, the contents of soluble cations and sodium adsorption ratio (SAR) were relatively low, but increased in the lower watershed of the Syr-Darya River. It is considered, on a geochemical scale, that the most mobile species, such as Na+ and Cl−, tend to be removed from the upper regions and concentrated in the lower watershed. In northern Kazakhstan, soluble cations were usually high in subsoils with a high proportion of Na. These salts were considered to be derived from fluvial deposits that extensively cover this region. Therefore, although rainfed agriculture is most common in this area, the risk of secondary salinization is high with the introduction of irrigation agriculture in the future. Thus, the salt contents in deep soil layers are primarily determined by geochemical factors, with the accessory factors of soil texture and topography (or water regimes) affecting the salinization risk in certain regions. In contrast to non-irrigated conditions, under irrigated conditions, the upper layers of soils usually accumulate higher concentrations of soluble cations compared to the 100–200 cm or even deeper soil layers, and as a result SAR increases, indicating a process of secondary soil salinization. There is a higher fundamental risk (i.e. by geochemical factors) for secondary salinization in the lower watershed of the Syr-Darya River and in northern Kazakhstan than in the alluvial fans, such as the Ili and Fergana basins. For sustainable maintenance of irrigation agriculture, further extension in the lower watershed of large rivers should be reconsidered.

Rehabilitation of saline soils by means of volcanic material coverings

SummaryThe scarcity of water in arid regions promotes natural soil salinization processes, which limit soil productivity, cause degradation and contribute to desertification. Human activity can speed up these processes although it can also help reduce their effects and even rehabilitate affected soils. A number of traditional soil water conservation systems used in farming are also techniques for reducing soil salinity. Examples include systems that involve the use of volcanic materials as mulch, a practice known as ‘arenados’ that has been common for decades in the Canary Islands. The present work examines short‐term changes in the salinity of two saline soils, one with clay texture and the other with loamy texture, both of which were covered artificially with a 12‐cm layer of basaltic pyroclasts. Monitoring over a period of 4 years, during which rainfall averaged 130 mm for the clay soil and 120 mm for the loam, revealed a decrease of approximately 76% and 86%, respectively, in the salinity of the top 40 cm of the profile in the two soils. The decreased salinity of the rooting zone, which is associated with an improved moisture regime in the covered soils has given rise to a form of dryland farming with acceptable yields in a soil environment which is otherwise poorly suited to agriculture.

Agriculture in the Oasis of the Manga Grasslands of Semi-Arid North-East Nigeria

Peasant farmers in the Manga Grasslands of semi-arid north-east Nigeria depend largely on agriculture for their livelihood. However, recurrent drought since the early 1970s has disrupted the traditional farming systems of the region, and hence the agriculture-based rural economy of the Grasslands. There is evidence that farmers in the Grasslands are obliged to intensify crop production in areas with ‘good’ soils and ‘adequate’ water supply, that is, the oases. The rich organic soils and the shallow, semi-confined water table beneath the oases are precious natural resources for intensive agriculture. These do not come without a price, however, as the rich, organic soils have the potential to be contaminated by acid sulphate and salt. It is expected that future soil creation, particularly under dry climatic conditions, will lead to the formation of true acid sulphate soils, and consequently, the twin processes of soil acidification and salinization will present real management problems for sustainable agriculture. It is concluded however, that under the prevailing soil, hydrological and climatic conditions of the oasis, sustainable agricultural production remains elusive.

Engineering salt tolerance in crop plants

Environmental stress caused by salinity is a serious factor limiting the productivity of agricultural crops, which are predominantly sensitive to the presence of high concentrations of salts in the soil. Although drainage and the supply of high quality water can solve the problem, these measures are extremely costly and not applicable in extensive agriculture. Salt has a detrimental effect on plants because it causes a water deficit, which results in osmotic stress, and because of the effects of excess sodium ions on key biochemical processes. To tolerate high levels of salts, plants should be able to use ions for osmotic adjustment and to accumulate these ions in the vacuole to keep sodium away from the cytosol. It has been shown previously that overexpression of AtNHX1 (a vacuolar Na+–H+ antiport) in Arabidopsis plants, allowed the transgenic plants to grow in 200 mm NaCl, suggesting that crop plants with improved salt tolerance could be engineered.Hong-Xia Zhang and Eduardo Blumwald 1xTransgenic salt tolerant tomato plants accumulate salt in the foliage but not in the fruits. Zhang, H-X. and Blumwald, E. Nat. Biotechnol. 2001; 19: 765–768Crossref | PubMed | Scopus (627)See all References1 now report the generation of salt-tolerant transgenic tomato plants. Whereas wild-type plant growth was severely inhibited by salt, the transgenic plants overexpressing an Arabidopsis vacuolar Na+–H+ antiport were able to grow and produce fruit in the presence of 200 mm NaCl (Fig. 1Fig. 1). The sodium and chloride content of the leaves of the transgenic plants was 20-fold higher that in untransformed plants. This increase in sodium content in the transgenic plants correlated with an increase in the amount of antiport protein and an increase in Na+–H+ antiport activity in the tonoplast vesicles of transgenic plants compared with the untransformed plants. More significantly, whereas the leaves of the transgenic plants accumulated high sodium and chloride concentrations, the tomato fruits displayed low sodium and chloride content.Fig. 1(a) Control and (b) transgenic tomato plants growing in the presence of 200 mm NaCl. (Photographs courtesy of Eduardo Blumwald.)View Large Image | Download PowerPoint SlideIn summary, these results show that the accumulation of sodium into the vacuoles, mediated by the vacuolar Na+–H+ antiport, allows crop plants to minimize the toxic effects of salinity. In spite of many years of conventional breeding for salt tolerance, only a few varieties, with only limited salt tolerance, have been released. Salt tolerance is a complex trait, and a long list of salt-responsive genes has been reported. One school of thought has concluded that salt tolerance will be achieved only after pyramiding several characteristics into a single genotype, where each one alone could not confer a significant increase in salt tolerance. However, Zhang and Blumwald's work shows that it is possible to generate crop plants that can tolerate high salinity levels with the modification of a single gene. This result suggests that with the incorporation of transgenic modification, breeding of salt-tolerant crops will be possible with far fewer target traits than has been anticipated. A substantial area of irrigated land has been damaged by the accumulation of salt, and the process of soil salinization is a permanent threat. The generation of salt-tolerant transgenic plants is an essential step toward solving the problem of feeding the world's rapidly growing population.

Causal processes of soil salinization in Tunisia, Spain and Hungary

AbstractSoil salinization arises due to the build up of soluble salts at or near the soil surface. Salts accumulate by primary and secondary processes that alter the soils physicochemical properties and lead to direct and indirect soil degradation. Results are presented here from the study of three contrasting salt‐affected landscapes. The Chott el Fedjadj, Tunisia, is a naturally salt‐affected basin containing saline sediments deposited during a marine incursion. The endoreic conditions lead to salt recirculation, concentration and reprecipitation. In the Guadalentin Valley, Spain, increased irrigated agriculture has led to aquifer overexploitation releasing gas and salts. Irrigating with the resultant contaminated groundwater has induced soil salinization. The salt accumulation and translocation is dictated predominantly by irrigation method, water quality and quantity. Hungary has the largest expanse of naturally salt‐affected soil in Europe, with the dominant soil type being solonetz. In Hungary the type of salt‐affected soil development is related to the salts present, hydraulic properties of the soil and depth and quality of the watertable. In Tunisia a catenary relationship of increased water and soil salinity towards the centre of the chott is found, whereas in Spain the highest salinities were found under flood irrigation with the valley displaying a complex spatial distribution of soil salinity. The sediment distribution in Hungary dictates that solonchak soils are found mostly in the Danube–Tisza interfluve and solonetz soils in the Tisza floodplain, with localized variations in soil type related to watertable characteristics. Copyright © 2001 John Wiley & Sons, Ltd.

Relationships between yield and irrigation with low-quality water — a system approach

With the increasing usage of brackish water in agriculture there is a need to quantify the water quantity and quality relationship during irrigation of crops. A model based on a system approach was developed, where the responses of plants to water and salinity stress are expressed in a structural system of equations. The model was applied to field crops in the Israeli Negev, in three case studies, using existing linear and non-linear relationships between yield and irrigation and between yield and salinity. Model coefficients were estimated from experimental data. Model results were consistent with actual yield of corn and cotton in the single season cases. Simulation of wheat growing in the winter with supplemental irrigation with brackish water for 13 years showed interesting results of accumulation of soil salinity and reduction of yield. The model can be easily applied to other crops and growing areas. It can be used for analysis of long-term soil salinization processes.

Soil Salinization Processes in Rice Irrigation Schemes in the Senegal River Delta

AbstractSoil salinization constitutes a major threat to irrigated agriculture (mainly rice, Oryza sativa L.) in the Senegal River Delta. It is generally hypothesized that salinization is caused by (i) capillary rise from a saline water table and (ii) concentration of salts in the field due to lack of adequate drainage facilities. The impact of field water management and rice cropping intensity on salinization in the Delta was determined using an electromagnetic conductivity meter (Geonics EM38). More than 4000 measurements were made in 40 rice fields on a typical heavy clay soil (Vertic Xerofluvent). Thirty EM38 measurements per field (0.25 ha) estimated average field soil salinity with a relative error of 20%. A multiple linear regression model based on EM38 readings explained 60 to 75% of the variability in conductivity of 1:5 saturation extracts at 0‐ to 5‐, 10‐ to 15‐, and 30‐ to 35‐cm depths. Higher cropping intensity limited upward salt transport from the water table. Average horizontal and vertical EM38 measurements increased in the following order: two rice crops per year with drainage: 0.73 and 0.98 dS m−1; one rice crop per year with drainage: 1.26 and 1.76 dS m−1; one rice crop per year without drainage: 2.23 and 2.98 dS m−1; and abandoned fields: 4.77 and 4.29 dS m−1. Results indicate a beneficial effect of flooded rice on salinity for this type of heavy clay soil. Irrigation development in the area needs to be accompanied by monitoring of water table depth.

A defense of the theory of progressive soil salinization in ancient southern Mesopotamia

AbstractAn explanation is given of the fundamental processes of soil salinization and degradation induced by irrigation of poorly‐drained river valleys in arid regions, and of why these processes were practically uncontrollable under the circumstances of ancient Southern Mesopotamia.

NATURE AND DISTRIBUTION OF SECONDARY SOIL CARBONATES WITHIN LANDSCAPES IN RELATION TO SOLUBLE Mg++/Ca++ RATIOS

The presence of magnesium-bearing calcites in secondary carbonate accumulation layers of soils is shown to be associated with soluble Mg++/Ca++ ratios of one or greater in the attendant or underlying layers. The dissolution of both calcite and dolomite within the solum and the precipitation of only calcite in the developing Cca leads to a buildup of Mg++ in the soil solution. If leaching depth is considerably below the Cca horizon, the secondary calcite is Mg free. If leaching is restricted to relatively shallow depths (2–4 m), the buildup of soluble salts and the increased soluble Mg++/Ca++ ratio which result are conducive to the precipitation of Mg-bearing calcites. Soluble salt distribution within a glacial till landscape suggests that surface runoff waters and snow accumulation in depressions are more important aspects of water distribution in such landscapes than is lateral movement within the soil itself. The accumulation of soluble salts in the 2 to 4-m zone of upland soils and the complete lack of salts to greater depths in depressions ties in well with the presence or absence of Mg-bearing calcites. The implications of the nature of the carbonates to soil salinization processes are indicated.