Developments in Soil Salinity Assessment and Reclamation

Soil salinity spreads in more than 100 countries, and no continent is completely free from salinity. The level of salinity problem varies trans-country and even within the country at different locations, landforms, and irrigated agriculture regions to farmers’ fields. Local climatic, environmental, and management conditions determine the salinity problem. Current global estimates reveal over one billion ha area affected to various degrees of soil salinization. Soil salinization in the coastal areas due to seawater intrusion developed very strongly saline soils called sabkha. Human-induced salinization occurs in irrigated agriculture farms due to poor management of soil and water resources, high water table, poor drainage conditions, and the use of saline-brackish water for irrigation with less emphasis on leaching fraction. There have been significant innovative advancements in technologies to assess, map, and monitor soil salinization spatially and temporally, from regional, national, to farm levels and submicroscopic scales. In this chapter, a comprehensive array of routine and modern techniques to address salinity issues at various scales using remote sensing and GIS, geophysical methods, and modeling are presented to guide stakeholders for the selection of appropriate technology to suit their needs and budget. A comprehensive review of such technologies and their applications has been included in this chapter, and salinity diagnostic procedures from regional to submicroscopic levels with relevant examples are described. Soil salinity classification systems used in various countries such as Australia, China, FAO-UNESCO, Russia, the USA, and Vietnam have been described. The chapter also presents global distribution of salt-affected soils.

Salinization is a progressive soil and water degradation process. Soil salinity can be natural or induced by human affecting aquifers and the most productive irrigated agroecosystems in arid and semiarid regions, representing an increasing environmental concern. Root zone soil salinity can be managed using advanced tools and adjusting irrigation application and using the concept of leaching requirement. Modeling the reactive transport in soil uses simplified representations of the reality, but can reveal complex interrelations of properties of the system under study, and is best suited for drawing scenarios for investigating “what-if…” questions. Each modeling effort tries to give answer to a particular question; hence, the input information required for running the models ranges in complexity as does the data acquisition efforts. The scale of application, geometry of the system, and biological, chemical, and physical processes represented, as well as the capability of representing an evolving system, are main differences among models. Some aspects important under normal agricultural practices are not well reproduced by some codes nowadays. Management practices, geometry of irrigation and evaporation, sinks of solutes (plant uptake), and interaction of fertilizers with soil components are incorporated in an uneven way in the available codes and should be further developed. Currently models become more and more mechanistic and require very intensive research efforts. There are uncertainties associated to the values of the input parameters, to the computation procedure, or to the inaccurate description of the system. The parameter estimation, analysis of sensitivity, and validation procedures are refinements applicable to most models. This chapter presents an overview of different modeling approaches, discusses the limits of application of models, and develops a study case.

The effect of rainfall, evaporation, and aridity on salt accumulation in the soil, on a national scale, is not straightforward, and other factors such as geology, position in the landscape, and previous climatic conditions should be considered. Good decisions for the management of salt-affected soils on a national scale require good information, derived from raw data. Such data must be generated with specific goals in mind, and it must be stored properly in a format that is easy to access and process. Like any basic resource, the data environment must be managed meticulously. In this study although data verification was previously done on most samples, much effort was devoted to data cleaning. Of the more than 40,000 original data points, only 22,404 data points were used due to the stringent cleaning protocol. A forward selection stepwise regression was used to simplify the various models. In a stepwise regression, variables are added or removed from a regression model one at a time, with the goal of obtaining a model that contains only significant predictors, but does not exclude any useful variables. The accuracy with which EC, ESP, and pH

water

were predicted with stepwise multiple linear regression relationships on a national scale is surprising, considering that the various models included all “outlier” values. The

R

2

statistic indicated that the models as fitted explained the variability in EC and ESP much better for the low rainfall class (<550mm annual rainfall), than for the high rainfall class (>550mm annual rainfall). For EC, <550mm annual rainfall class in the model explains 58% of the variability and for >550mm annual rainfall class 39% of the variability. Values for ESP are 85% for <550mm annual rainfall class and 52% for >550mm annual rainfall class.

Thailand is an agrarian country with a total land area of 51.4 × 10

6

hectares (ha), of which 38% are farm land, 25% are forests, and the remaining 37% cover urban area, public area, sanitation, swamp land, railroad, highways, real estate, and others. Thailand has been changed in the last five decades due to rapid population increase and land use pattern change. The encroachment of natural forests, use of marginal lands, and mismanagement of soil and water resources have degraded soil and water resources. It is estimated that degraded soils cover 31 × 10

6

ha or 60% of the total land area of the country, comprising six major soil problems, that is, acid sulfate soils, peat soils, sandy soils, eroded soil, mined soils, and saline soils. Saline soils are the oldest and represent one of the most important environmental problems to humanity. In Thailand, they occupy 3.5 × 10

6

ha area. These soils reduced the agricultural productivity in the northern region, northeastern region, the Central Plain, and along the coastal areas of the country. It is therefore important to assess and monitor soil salinization in these areas for better management of agricultural soils. This has been accomplished in Boe Klue District, Nan Province, Northern Thailand. The methodologies used are geophysical method, ground-based surveys using EM38 measurement and laboratory analysis of soil and water samples. The result showed the occurrence of salt on soil surface being derived from soil salinization as a natural phenomenon. The source of salts is found to be from strike slip of Boe Klue formation. Salinized soils have been found to coincide with shallow saline groundwater or exposure of Boe Klue formation.

Almost 50% of the irrigated lands of Central Asia are affected by different levels of salinity. In extreme cases, the most severely affected lands are abandoned, while moderately saline lands produce low crop yields. Rehabilitation of the saline lands could have significant implications on productivity of irrigated lands as well as positive impacts on the environment. The assessment of the trend and the scale of salinity are crucial element in the development of a remediation/rehabilitation strategy. The traditional approach for soil salinity mapping is extremely costly and has low level of precision. The chapter discusses the approach in developing the soil salinity maps by analysis of vegetation stress from multi-temporal remote sensing data for irrigated areas.

Among the numerous adverse processes related to the soil and the environment is the soil salinization, which affects more extended areas posing a real global problem. This chapter presents a new soil salinity map, which was compiled with the aim of specifying the information on geographical distribution and peculiar features of soil salinization in the vast areas of the Russian Federation. The new map of soil salinity as well as the map of chemical composition in salinization at a scale of 1:2,500,000 allowed identifying the main regularities in geographical distribution and genesis of salt-affected soils in Russia. This information helps to give the comparative characteristics of soil salinization in different regions of the country.

Soil salinity in the arid and semiarid environments is a major concern for the sustainability of agriculture and water management. Salinity problem does exist in Egypt as well. In this study, we attempted to map soil salinity in a narrow strip in Sinai Peninsula. This was accomplished by analyzing surface soil samples for electrical conductivity (EC dS m

−1

) and using Landsat TM image acquired in 1991 with a 30-m resolution that covered the study area to measure the mean reflectance pixel values at these specific samples’ ground locations. Landsat TM data was preprocessed (geometrical and radiometrical). Forty bands ratios were developed from the 6 TM original bands to select the bands required for this particular need. A correlation matrix was developed to select the best regression model to represent a soil salinity map. Significant correlation was shown between the inverse of 3 reflectance TM bands and the premeasured EC values (

r

= 0.82, 0.79, 0.62 at 0.01 level for inverse of TM1, TM2, TM7, respectively). Linear regression model,

y

=

c

1 +

c

2(1/TM1) +

c

3(1/TM2) +

c

4(1/TM7), with correlation of determination

r

2

= 0.72 was developed for soil salinity mapping. Thus, by applying this equation to the inverse of Landsat bands 1, 2, and 7, a soil salinity map was prepared. It is concluded that remote sensing is useful technique and can be considered a reliable, cost-effective, and timely method needed to determine the extent of soil salinity.

Quantitative assessments of the temporal variability in soil salinity are discussed in this chapter. Currently such assessments are based on the comparison of point-size data for several years (regular observations and sampling in the same point) or on the comparison of soil salinization maps developed in different years. Both methods have drawbacks. In the case of point-size data, it is difficult to extrapolate them on large territories. In the case of comparison of two soil maps obtained in different times, the problem of temporal extrapolation of the data arises. We estimated the dynamics of soil salinization on the basis of remote sensing materials with ground-truth calibration for the territory of the Usman Yusupov farm in the Golodnaya Steppe of Uzbekistan. Remote sensing materials on this territory were obtained for years 1983, 1985, 1986, 1988, 1989, 1990, 2000, and 2008. On their basis, eight separate soil salinity maps were developed for the area of 80 km

2

. A comparison between them made it possible to develop a series of the maps of soil salinization dynamics. Separation of the areas with a stable soil salinity status upon the comparison of the maps for different years proved to be very informative. Such areas comprised no more than 1.5% of the farm area for the whole period (25 years) and about 25% of the farm area for two consecutive years. Quantitative data on soil salinization dynamics made it possible to outline certain drawbacks in soil reclamation procedures and to suggest the ways of their optimization.

Soil salinity in the central arid region of Iran is mainly due to dry climate, salt-rich parent materials, insufficient or lack of drainage and use of saline groundwater for irrigation. Esfahan province is located in the central arid region of Iran. Of 105,000 km

2

total area, an area of 5,000 km

2

is used for crop and fruit production. Soil and water salinity is the major limitation to achieve optimum crop yields. The soils are classified as Entisols and Aridisols. Soil salinity is distributed in nine physiographic land forms, namely, mountains, hills, plateau, piedmont plain, alluvial plain, lowland, flood plain, colluvial fan and alluvial fan. In this study, salinity data were obtained from soil survey project reports conducted in the last decade. The data showed the ECe varied to a large extent. The highest and lowest average salinities were 38.3 dS m

−1

in the lowland (high evaporation and ground water table) and 0.6 dS m

−1

in the mountainous area, respectively. High precipitation over evaporation in the mountainous area of west leached salts from soil profile. The ECe values are moderately high to extremely high in the east part of Zayandeh-Rud river plain due to fine soil texture and poor drainage. In the river plain, irrigation often causes secondary soil salinization. More work is required to establish real causes of soil salinization and spatial distribution in the province. However, it is evident that salinity distribution is highly variable in the central arid region of Iran and in different physiographic unit of land area. Future development of agriculture and industry in each landform should consider the present and future soil salinity potential. Given the importance of irrigated agriculture and the shortage of water supply, more ground-based soil and groundwater salinity monitoring schemes are needed as a prerequisite of land use in the region.

The knowledge about the magnitude, the spatial extent, the distribution and the evolution of salinity over a period of time is essential for the better management of salt-affected soils. Soil salinity is determined, conventionally, by measuring the electrical conductivity of a saturated past extract (ECe). However, given the spatio-temporal variability of salinity, numerous samples are necessary, which makes the conventional procedure laborious and expensive. As an alternative, the apparent electrical conductivity of soil (ECa) can be measured in the field by the use of the electromagnetic induction (EMI) method. This method is fast and allows making extensive ECa determination in space and monitoring. In the present study, an area of 2,060 ha has been investigated in the irrigation district of Tadla, central Morocco. Twelve soil samples were collected for ECe measurement, while 92 ECa measurements were realized with EM38. The pairs of ECe-ECa values allowed establishing the calibration equation permitting to convert the ECa into ECe values and for other ECa values for which ECe was not accomplished. The geostatistics was used to develop maps for the risk of soil salinization. Initially, a threshold for the risk of soil salinization was determined, and indicators were built. Later, the spatial variability of these indicators was described and modelled using the variogram. Finally, the maps were generated based on a non-parametric method of geostatistical interpolation, that is, indicator kriging. The results showed that the study area presents various degrees of soil salinization risks. The south-eastern part and small areas in central west and east of the study area have a low risk of salinization. In contrast, the south-western, the north-western and the central parts have a high risk of salinization. All the remaining parts of the study area have a moderate risk of salinization. It is concluded that the combined use of ECe and ECa-EM38 values and geostatistics allowed establishing a reliable soil salinization risk map and help to develop rehabilitation plan for the salt-affected soils.

Agricultural productivity may be constrained by many factors such as water scarcity, soil degradation, and use of marginal quality water. In Morocco, the main degradation processes occurring for irrigated areas are on-site impact (soil salinization and/or alkalinization) and off-site impacts (pollution of groundwater by salts and nitrates). Since 1995, the Moroccan Public Irrigation Agency has installed and maintained a network of soil and groundwater monitoring stations. For the present study, we selected the soil and water sampling sites on spatial representativeness in the perimeter, the main soil types, and the hydrogeological variants. Soil salinity, alkalinity, and sodicity as well as groundwater salinity, nitrates, and water table level were recorded to determine spatiotemporal variability and dynamics of groundwater salinity. A good understanding of its evolution in space and time will make possible to obtain reliable models for spatiotemporal prediction, estimation of the missing data, cartography, and over the long term for the delineation of risky zones. The spatiotemporal analysis of the groundwater salinity shows the presence of a strong spatial dependence and a weak temporal dependence. The spatiotemporal dependence of the residuals is very weak and primarily consists in random fluctuations. Consequently, a simple model was adopted, containing two components: a spatial component explaining more than 50% of the total variability of groundwater salinity and a temporal component that explains almost 77% of the remaining variability. Overall, this model explains more than 90% of total observed variability. Cartography of the average groundwater salinity was also established by kriging, by computing mean spatial variograms on the basis of per site data. The spatial variogram of the northern area was adjusted by the Gaussian model characterized by a sill of 3 dS

2

/m

2

and a range of 12,526 m, while the southern area was adjusted by a Gaussian model with a sill of 0.2 dS

2

/m

2

and a range of 9,674 m, with a nugget effect of 0.06 dS

2

/m

2

.

The assumption of zero trend seems unlikely for many soil properties that change systematically across the landscape. Removal of a trend may result in a bias in estimating the semivariogram and in many studies has not resulted in apparent improvements in kriging estimates. This study was conducted with the objective to use a proportional effect semivirogram model approach for handling a region with a pronounced trend aside from trend removal. To demonstrate this approach, soil samples (0–30-cm depth) were collected along four transects and analyzed for the electrical conductivity (EC) of the soil/water (1:5) extracts. The 50-m long transects centered on the points (

x

j

) were from four subregions with maximum contrast in salinity means [

m

(

x

j

)]. Fractile diagrams and goodness-of-fit analysis at the 0.05 significance level indicated that the normal distribution function fitted the EC values of the four transects. Except for transect T(

x

1

), a lognormal distribution function might also be accepted. A proportional effect stationary semivariogram model:

$$ {\gamma }_{{e}}(h,{x}_{j}){ /}\Phi \left[m({x}_{j})\right]={\gamma }_{s}(h)$$

was fitted to the local experimental semivariograms

γ

e

(

h

,

x

j

) by the steepest-descent optimization method. The predicted local dispersion variances were reasonable when compared with the experimental variances thereby supporting validity of the proposed model. Statistical analysis of cross validation (kriging) results confirmed the adequacy of the stationary semivariogram model and the validity of the estimated parameters. The assumption of quasi-stationary instead of stationary along the transect improved predictions of true kriging variance. The proportional effect quasi-stationary semivariogram models may offer a possible approach for krig handling a regionalized variable having a pronounced trend without the need for trend removal.

Mapping, updating, and managing soil salinity are considered difficult tasks due to the large spatial and temporal variability of salinity phenomena. In the present study, GIS and field studies are integrated on an area of 22,019 ha to monitor soil salinity development during 2002–2009 in Sinnuris District soils, Fayoum, Egypt. Results have shown decrease in areas of soil salinity from 42.57 to 29.5% within the studied period, mainly due to subsurface drainage networks system and soil reclamation activities. The saline soils in the study area are classified as Typic Aquisalids, Typic Haplosalids, and Typic Salitorrerts. Based on the updated soil studies, groundwater, and Digital Elevation Models (DEM), a strategic management plan supplemented with GIS spatial maps (semi-detailed GIS maps of soil characteristics) is suggested to improve salinity conditions to overcome the future challenges of water scarcity in the area. Future prospective GIS models were produced to simulate drainage condition at groundwater level and to improve salinity conditions in the study area. The study is of vital importance for decision makers for the management of natural resources in Fayoum Governorate.

Geographical distribution of soil salinity, alkalinity, calcicity, soil texture, and organic matter (grid system-log distance of 2 km) has been evaluated and mapped in the study area (about 770 km

2

) using GIS-ILWIS format. It is found that in the soils of Tamia District, ECe ranged between 1.22 and 22.4 dS m

−1

and 1.03 and 97.1 dS m

−1

in Fayoum District soils within the top layer. Results show 91.5% of Tamia soils and 56.5% of Fayoum District soils present ECe > 4 dS m

−1

, indicating that salt-affected soils are distributed throughout the study area. About 94.5% of Tamia soils and 30% of Fayoum soils are calcareous (>10% CaCO

3

eq), due to the nature of parent material from which these soils are evolved. Soil pH of more than 8.00 was found in about 3.25% of Tamia soils and 73% of Fayoum District soils, whereas the soils with pH >8.5 are 3.96% in Tamia and 9.53% in Fayoum District. The organic matter contents seldom exceeded 1% in Tamia soils and did not exceed 1.5% for Fayoum soils. Soil texture in both districts is found as clay, sandy clay, sandy clay loam, sandy loam, and sandy. The maps generated through GIS are useful for decision makers for land use planning, conservation, and uses, as well as interest to researchers and soil science students to use the information for further investigations.

The sagebrush-steppe of the northern Great Basin, USA, receives 120–500 mm of precipitation per year. Clay horizon formation in these semiarid/arid Pleistocene-lake landscapes allows development of seasonal wetlands (vernal pools) that are recognized critical habitat for several native animal species. Most pools were dug out to create livestock water holes in the early and mid-1900s. Restoration efforts are underway to restore these ecosystems. This study was undertaken to evaluate the pre- and post-restoration hydrology of several regraded vernal pools. Five total sites, one undisturbed and four dugouts, were mapped for apparent electrical conductivity (EC

a

) using electromagnetic induction to evaluate hydrologic flow patterns. Two sites were subsequently regraded to fill in dugouts and redistribute excavated piles. EC

a

for the restored sites was remeasured 1 year later. EC

a

patterns of the dugout pools indicate that the hydrology is directed toward the low areas concentrating soluble salts in the dugout through evaporation. Patterns of the undisturbed site suggest a broader distribution of water and salts. Conductivity patterns of post-restoration show a marked difference in conductivity with a broadening out of the high-concentration area and a decreased difference between the former dugout area and surrounding area. The pattern after 1 year of hydrologic activity suggests that regrading allows the water to spread across a larger area and begins to develop hydrologic patterns similar to undisturbed pools, suggesting potential to restore desired ecological function. Results of this study will refine understanding of vernal pool hydrology and ecology for the region.

Salt-affected soils in the canal commanded area of Jammu (Jammu and Kashmir) have been mapped on scale of 1:250,000 using remote sensing data from IRS LISS III satellite imagery. Ground truthing was made through field survey to characterize salt-affected soils under Ravi-Tawi canal command area. The canal command area is mainly located in the Kathua and Jammu districts in Jammu and Kashmir state, North India, and covering an arable area of 75,000 ha. The land use and landscape variability was assessed through integrating RS imagery and ground truthing. It has been found that an area of 25,670 ha becomes unproductive due to salinization and waterlogging. The soils are very strongly alkaline (pH 9.9), with dominance of exchangeable Na (ESP 25.3) and sodium adsorption ratio (SAR) of 78.41 (mmoles L

−1

)

0.5

. Amongst cations, Na was dominant followed by Ca, Mg and K. The highest ESP was recorded in Tarore soil with ustic and aquic moisture regimes associated with hard surface crust, calcic and natric sub-surface horizons. Gypsum requirement (GR) to amend soil sodicity was measured on representative soil samples and applied at 100% GR basis; this application has increased rice and wheat yields 43.3 and 86.9%, respectively, over control treatment. Soil properties were also improved noticeably, pH was decreased from 9.70 to 8.84, bulk density decreased from 1.52 to 1.48 Mg m

−3

and infiltration rate was slightly improved.

Low rainfall, high temperature, and the past human activities resulted serious salinity problems in today’s agriculture in the Sultanate of Oman. Secondary soil salinity has increased rapidly due to the persistent use of saline groundwater, and the extent is increasing due to increased pumping in Batinah region. The balance existing between total pumping and annual recharge before the 1990s has been disturbed that has resulted in the reduction of crop yields and gradual abandoning of lands for agriculture. In addition, seawater intrusion due to overpumping also occurs. In the year 2005, about 18.9–36.0 × 10

6

US$ was lost due to salinity. To tackle salinity problem, a project was undertaken at Sultan Qaboos University to mitigate soil and water salinity. The project focused on four approaches: soil rehabilitation, biosaline agriculture, fodder production, and integration of fish culture into crop production. The project was initiated with the objectives to develop scientifically sound and environment-friendly guidelines for farmers (a) to sustain cost-effective agricultural production in saline agriculture lands irrigated with saline groundwater, (b) to improve food security of Oman, and (c) to combat desertification in agricultural lands to avoid abandonment. The salt-tolerant varieties of tomatoes, barley, sorghum, and pearl millet have shown promising results for successful cultivation in saline soils. Surface mulching with a thin layer of shredded date palm residues resulted in lesser salt accumulation and more crop yield than other methods. The fodder grown in saline soils using saline irrigation water did not affect growth and meat quality of sheep fed with this fodder. The incorporation of aquaculture in saline areas was proven feasible and profitable.

A large area of Pakistan is suffering from salinity problem. Being situated in arid and semiarid region, the process of salinization and sodification remains in progress. Bringing these marginal lands into agriculture production is essential from food security perspectives for rapidly growing population. To develop comprehensive technology for the reclamation of these soils, field experiments were conducted to grow rice crop in salt-affected soil using different amendment technologies. The treatments used were

T

1

= control,

T

2

= 100% gypsum requirement (GR),

T

3

= 50% GR with wheat straw at 2 t ha

−1

,

T

4

= 50% GR with rice straw at 2 t ha

−1

, and

T

5

= 50% GR with rice and wheat straw at 2 t ha

−1

in the ratio of 50:50. The

N

,

P

, and

K

were applied at 100, 80, and 60 kg ha

−1

, respectively. Fertilizer sources were urea, triple super phosphate (TSP), and sulfate of potash (SOP) for N, P, and K, respectively. Canal water was used to irrigate the crop based on crop requirement. The results revealed that rice biomass and paddy yield was increased significantly in all the treatments over control. Biomass of 14.60 t ha

−1

and paddy yield of 3.50 t ha

−1

were achieved in

T

2

(100% GR) compared to the values under control treatment, that is, 7.22 and 1.62 t ha

−1

for biomass and paddy yield, respectively. The yield in treatment

T

5

was close to the highest yield obtained in

T

2

. Post harvest soil analysis indicated the decrease in ECe, pHs, and SAR values in all the treatments compared to the values in control.

Appropriate use of marginal-quality waters coupled with crop rotation(s) and management interventions on saline-sodic soils have the potential to transform such water and soil resources from environmental burdens into economic assets. Several long-term field studies in the Indus basin of Pakistan were carried out to evaluate different irrigation and soil management options of using saline-sodic waters on saline-sodic soils for reclamation in a rice-wheat production system. The effect of different amendments like gypsum (gypsum requirement on water RSC basis and on soil SAR basis) and farm manure along with conjunctive use of fresh and saline-sodic waters for irrigating rice and wheat crops was evaluated. The effects of applied amendments were evaluated in terms of change in the physical and chemical properties of soils, yield-based crop growth response and economic implications. The results showed significant improvement in physical and chemical properties of soils with good yields of crops with the application of amendments specially gypsum and farm manure along with conjunctive use of fresh and saline-sodic waters. Salt removal (kg ha

−1

) was the highest with the application of two pore volume (PV) water. In general, it was concluded that after the application of four irrigations of different PV, highest leaching fraction removed maximum salts from loamy sand soil. Salt removal remained the highest with first two irrigations and then decreased subsequently. Overall, the greatest net benefit was obtained from gypsum plus cyclic use of saline-sodic and fresh waters. It was found that the farmers’ management skills were crucial in the overall success to improve crop yields during reclamation of saline-sodic soils. Based on the results, we propose that saline-sodic water could be used to reclaim saline-sodic soils by using a rice-wheat rotation and a site-specific combination of soil amendments and water application strategies.

A major portion of the area under cassava in India is under irrigated Vertisols, and the farmers face a number of soil-related constraints which significantly reduce the tuberous root yield of cassava. In order to reclaim these arid lands and to increase the yield and profitability of farmers, farmer-friendly technologies have been developed based on field experiments conducted during the past 7 years since 2003. Three different on-farm experiments were conducted to study these problems and to develop a sustainable reclamation strategy. Major components of the technology include adoption of deep tillage with a chisel plough, application of neem cake, application of biofertilizers such as N fixer, P-solubilizing bacteria and AM fungi and biocontrol agents like

Trichoderma

and

Pseudomonas

. Besides this, a balanced fertilization schedule based on site-specific nutrient management (SSNM) approach have also been developed to address the problems due to imbalance in nutrient applications by farmers in those arid environments. Studies have shown that these technologies have resulted in significant increase in tuberous root yield and income of farmers besides improving soil health and soil quality.

Two major types of salt-affected soils were distinguished in the study area: saline and alkali (sodic) soils. Saline soils have an excess of neutral soluble salts such as chlorides and sulphates of Na

+

, Ca

2+

and Mg

2+

. Plant growth is adversely affected due to reduced water uptake and ionic imbalance and/or nutrient stresses. Alkali soils, on the other hand, have Na

2

SO

4

and NaHCO

3

which upon hydrolysis produce alkalinity leading to high pH and exchangeable sodium, nutrients unavailability and low yields. The reclamation technology involves integrated use of amendments like gypsum for rice-based cropping system, balanced and integrated use of chemical fertilisers and organic/green manures improving soil health and input-use efficiency. In saline soils, leaching with good-quality water and sub-surface drainage is essential. Use of poor-quality ground water constitutes about 30–80% of total ground water. The management practices for optimal crop production with saline and sodic water irrigation must aim at preventing the build-up of salinity/sodicity and toxic ions in the root zone, to levels that limit the productivity of soils, control the salt balances in soil-water system as well as minimise the damaging effects on crop growth. Efficient, balanced and integrated nutrient management strategies are extremely important to increase yields to match the potential yields obtained under good-quality irrigation water. Therefore, we focus on the ionic interactions and nutrient dynamics as influenced by salinity/sodicity of irrigation water and discuss how these issues relate to the nutritional problems and suggest long-term remedial measures to utilise poor-quality waters for improving and sustaining crop productivity of salt-affected soils.

The anionic polyacrylamide (PAM) is recently used to rehabilitate saline and sodic soils and control soil erosion. The research on the effectiveness of anionic PAM along with gypsum or lime application on soil erosion is rare and poorly documented. Therefore, an experiment was conducted to study the effects of anionic PAM with or without gypsum on the erosion of soils under saline/sodic conditions. For this purpose, a clay loam soil was prepared to achieve three levels of exchangeable sodium percentage (ESP) 0.5, 9.9, and 25.5 with an appropriate solution of salts. Soil samples were air-dried and packed in the trays. Powdered PAM, gypsum, or a mixture of both was applied to the salt-treated soils. Thereafter, the soils were subjected to simulated rainstorm of 40 mm h

−1

by a fixed rainfall simulator. Saline waters with different levels of electrical conductivity (EC

w

): 0.1, 2, 5, and 8 dS m

−1

were used for simulated rains during the study. PAM amendment substantially controlled the erosion of the soils. The ESP was directly associated with the soil erosion and runoff. Among the treatments, the resistance to soil erosion was developed in the order of PAM > gypsum ≈ saline water > PAM mixed with gypsum ≈ PAM mixed with saline water. The magnitude of runoff water was reduced both by gypsum and saline water, whereas it was enhanced by PAM application. The mixed addition of PAM with gypsum or salts exacerbated water erosion of soils.

Saline soils in Pakistan are of three types. First type includes porous saline and saline-sodic soils (4.79 × 10

6

ha) located in irrigated areas. These soils possess electrical conductivity in the range of 10–15 dS m

−1

and can be cultivated with salt-tolerant wheat. A short-duration and short-stature wheat line (SSt) was developed for such areas which is also resistant to lodging that may occur as a consequence of irrigation. The second types of soils (1.5 × 10

6

ha) have twin problems of salinity and water deficiency and are located in water-deficit areas of southern Punjab and parts of Sindh. A drought-tolerant wheat line (DTL) was developed for these areas which can be grown with only pre-sowing irrigation and can produce grain yield of about 6,000 kg ha

−1

. The third types of soils (11 × 10

6

ha) are located in Cholistan, Thar, Thal, and Kharan areas beset with salinity, high rate of evaporation, and strong winds. Water is most critical and limiting factor that prohibits agriculture production under such areas. Wheat variety “DURUGEN” was developed for these soils which combine tolerance for salt, water deficiency, and high temperature. It can be cultivated in desert areas for production of green biomass which can be used (1) as fodder to raise sheep and goats, (2) to provide green cover to barren lands thereby improving both land and the environment, and (3) to help providing livelihood to the poor natives. This chapter provides details of specific wheat genotypes and successful cultivation of these genotypes on saline soils.

It is well known that most saline soils have salt accumulation at the soil surface and the root zone due to the capillary movement of saline groundwater and subsequent evaporation. The criteria for classifying soil as saline taxa are different in different soil classification systems. In Chinese Soil Taxonomy (CST), soils that have a salic horizon starting within 30 cm from the soil surface are named as Orthic Halosols. In the World Reference Base for the Soil Resources (WRB), soils that have a salic horizon starting within 50 cm from the soil surface are named as Solonchaks. In the US Soil Taxonomy (ST), soils that have a salic horizon starting within 100 cm from the soil surface are named as Salids. In China, a large area of saline soils was reclaimed for crop production. This chapter describes some soil profiles that were classified into saline taxa in CST, WRB, and ST before they are reclaimed, to see if these soils, after a long history of irrigation, are still classified into saline taxa in the three soil classification systems. The results showed that the salts were leached into certain depth, the salic horizons were observed at different depth from the surface, many profiles could not be classified as Orthic Halosols as identified earlier, some of them could not be classified as Solonchaks, and few of them even could not be classified as Salids. With a long irrigation history, the depth of salic horizon is related to the amount of irrigation water and irrigation models. When more water was used for irrigation each time, the salts were found at deeper layers. Relatively the surface irrigation leached the salts deeper than the drip irrigation. According to the present study, we suggest that the criteria of ST should be taken in order to keep the reclaimed saline soils in the saline taxa, i.e., soil classification should not be changed by irrigation. We also suggest that more soil survey should be taken for discovering how much water was used in normal irrigation models and how deep the salts were leached under such normal irrigation models. Through analyzing large amount of data, especially those data coming from reclaimed saline soils, the depth and index for salic horizon should be redefined to keep the reclaimed saline soils in the saline taxa of soil classification systems. In this chapter, we examined the criteria of saline soil classification and made some suggestions by citing other scholar’s research results published in the scientific literature.

Existing high-quality water supplies are not sufficient to sustain irrigated agricultural production in arid and semiarid regions. Use of marginal-quality waters and reuse of agricultural drainage waters and treated municipal wastewaters are currently the only economic options for maintaining production in these regions. Marginal-quality waters are characterized by one or more of the following: elevated salinity, sodicity, pH, alkalinity, dissolved organic matter, and toxic elements such as boron and selenium. These water characteristics have a potentially adverse impact on crop productivity as well as soil physical properties. However, these waters can generally be used with proper management considerations. Model simulations of irrigation with saline waters confirm field data indicating that existing leaching guidelines overestimate water quantities needed for salinity control in the root zone. Leaching recommendations must also consider efficient water use, costs of water, nutrients, and disposal of drainage water as well as crop production. The sodicity hazard associated with application of saline water has been generally overlooked, due primarily to lack of consideration of the adverse impact of even small quantities of rain on physical properties of the soil surface. Recent long-term studies on infiltration of degraded waters indicate that the sodicity hazard to soil physical properties is greater than currently considered and that surface addition of gypsum may need to be more generally utilized. The utility of computer modeling as an aid to irrigation management is further demonstrated by the simulation of intermittent use of high-boron waters currently deemed unsuitable for irrigation. Future salinity research is critical to meet food demands of arid and semiarid regions of the world, especially for development of new varieties improving the salt and boron tolerance of sensitive species and improved prediction of plant production under multiple stress conditions (salinity water nutrient and toxic element).

Desertification of arable lands due to urbanization, global warming, and low rainfall mandates water conservation and using low-quality/saline waters for irrigation. Use of low-quality irrigation water imposes more stress on plants which are already under stress in these regions. Thus, there is an urgent need for finding salt/drought-tolerant plants to survive under stresses. Since the native plants are growing under such conditions and are adapted to these stresses, they are the most suitable candidates for use under arid regions. If stress-tolerant native species are identified, there would be a substantial savings in inputs in using them under stressful conditions. Present studies on saltgrass (

Distichlis spicata

L.), a euhalophyte, have shown it to have excellent drought/salinity tolerance, making it well adapted to harsh desert conditions, with great potential for use in urban landscape and agricultural settings to combat desertification and reclaim arid saline soils. The objectives of this study were to find the most drought-tolerant saltgrass genotypes for use in arid regions, where limited water supplies coupled with saline soils result in drought/salinity stresses, for use in sustainable desert agriculture, urban landscapes, and in biologically reclaiming desert saline soils. Various saltgrass genotypes were studied to evaluate their growth responses under progressive drought stress. Though all the grasses showed a high level of drought tolerance, there was a wide range of variations observed in their stress tolerance levels. Superior stress-tolerant genotypes were identified which could be recommended for sustainable production under arid regions and combating desertification.

Increasing population growth, particularly in urban centers, is resulting in critical freshwater shortages for both agriculture and urban use worldwide. To counteract existing water crises, many governments are restricting use of freshwater sources for irrigation. In the urban setting, governments are requiring use of reclaimed wastewater or other secondary saline water sources in lieu of freshwater for landscape irrigation.

Lolium

spp. (ryegrasses) is widely used for forage as well as in urban turf landscapes. Relative salinity tolerance of 35

Lolium

spp. cultivars was determined in solution culture by measuring changes in shoot weight, root weight, rooting depth, and % green leaf canopy area, relative to control (non-salinized) plants. There was a wide range in salinity tolerance of the tested cultivars, ranging from salt tolerant (e.g., cv. Paragon) to salt sensitive (e.g., cv. Midway). All shoot parameters were highly correlated, being mutually effective predictors of salinity tolerance. Root dry weight, significantly correlated with all shoot quality and growth parameters, was also effective in predicting relative salinity tolerance. However, rooting depth was not correlated with other parameters, and therefore not effective in predicting relative salinity tolerance. Based on these results, it is concluded that salt-tolerant cultivars exist within

Lolium

spp. for agricultural forage and urban landscape use.

Australia is listed under group II which represents countries that face economic water scarcity in 2025. Groundwater resources are the main source of water supplies for 30% of the world’s population. We have studied the use of saline groundwater to grow four turfgrass species (

Paspalum vaginatum

,

Sporobolus virginicus

,

Distichlis spicata

– three halophytes; and

Pennisetum clandestinum

– a non-halophyte) over two years under saline irrigation (13 dS m

−1

) groundwater or with freshwater, both at approximately 60% replacement of net evaporation. Soil salinity was assessed with the EM38, and by soil sampling and subsequent analyses for EC, a strong correlation was found between the two methods (

r

2

= 80%). Irrigation with saline water reduced turfgrass colour (i.e. ‘greenness’) in

Pennisetum clandestinum

whereas it was not affected in

Distichlis spicata

,

Paspalum vaginatum

and

Sporobolus virginicus

. Growth, represented by turf height increased by 3, 10 and 3 cm under saline irrigation for

Paspalum vaginatum

,

Sporobolus virginicus

and

Distichlis spicata

, respectively, whereas decreased by 1 cm for

Pennisetum clandestinum

. Na

+

concentration in leaf tissues increased threefold more in

Pennisetum clandestinum

compared with the halophytic grasses. Elucidation of quantitative relationships between growth, root-zone salinity and water content will improve basic knowledge on the functioning of halophytes managed for turfgrass and contribute to the sustainable management of these species under saline irrigation conditions. This chapter illustrates the potential use of the halophytic grasses as high-quality turfgrasses.

This chapter presents results of a 3-year field investigation in a vineyard located in Sicily (Mazara del Vallo, Trapani) within the framework of the Project “

Evolution of cropping systems as affected by climate change

” (CLIMESCO). Soil-plant responses to two saline irrigation waters were determined by measuring soil hydrological characteristics, soil salinity, crop transpiration and stomatal conductance in field plots of a Sicilian vineyard. The results proved that crop transpiration (

T

r

) and stomatal conductance (

G

s

) were significantly affected by soil salinity conditions, expressed by electrical conductivity of soil saturation extract (EC

e

). Significant reductions in

T

r

and

G

s

were found in plants irrigated with water of EC

w

= 1.6 dS m

−1

(L) compared to

T

r

and

G

s

values in plots irrigated with water EC

w

= 0.6 dS m

−1

(R). Significantly higher crop water stress index (CWSI) values, indicating stronger stress conditions, were measured in the L treatment, relative to the R treatment. Validity of the linear relationship between relative yield and relative transpiration was confirmed. A value of 0.7 for the yield response factor (Ky) provided accurate prediction of yield reduction in years 2008 and 2009. Reductions due to soil salinity, calculated according to Maas and Hoffman equation, showed that under conditions of water and salinity stress, yield reduction due to salinity represented a percentage of the total yield reduction of up to 11% in the L plots and up to 3.5% in the R plots. The investigation also indicated that EC

e

(1.5 dS m

−1

) discriminated a different plant response to salinity, indirectly confirming the Maas threshold value for grapes. Under the irrigation conditions in the Sicilian vineyard, it is suggested to implement management strategies aimed at keeping soil salinity below this threshold value. This can be realized by using low-salinity irrigation water only or by alternating the two irrigation sources.

Saline water use is one way of water saving in water-scarce regions. It allows preserving drinking water for other uses. In Tunisia, pearl millet (

Pennisetum glaucum

(

L

.)

R

.

Br

.) is mainly cultivated under irrigation in the arid and saline areas. Therefore, it is essential to make selection of salt-tolerant genotypes. It offers a scope for understanding the traits related to tolerance and to integrate these tolerant crop species/genotypes into appropriate management programmes to improve the productivity of the saline soils. Identifying autochthonous ecotypes growing under local agricultural conditions with significant levels of beneficial factors may promote the value-added cultivation and enhance the agricultural economy. The objective of this study was to identify morphological and physiological traits for salinity tolerance in Tunisian autochthonous ZZ pearl millet ecotype under local conditions. The ability of this ecotype to cope with severe salt stress is the combined characteristic of many plant features, both morphological and physiological. These mechanisms enable ZZ pearl millet ecotype to store the large amounts of salt in the leaves while maintaining high leaf water content and without a grave consequent on panicle yield.

Freshwater resources are not enough to meet the ever increasing demand of the agriculture sector to feed the growing population. Owing to this reason, agriculture scientists are exploring different ways to use saline water as an alternative source for crops. Samphire (

Salicornia bigelovii

Torr.) is one of the best candidates for such plants that can be grown using seawater. It has high culinary value and can be consumed either cooked or raw. The plant can also be used as feed for different domestic animals. Since its seed contains high-quality unsaturated oil (30%) and proteins (40%), it can be used to make biodiesel and as animal feed. At the Dubai-based International Center for Biosaline Agriculture (ICBA), a field experiment was conducted using five different lines of

Salicornia bigelovii

irrigated with seawater. In general, all of the Salicornia lines grew well and gave good results. To evaluate their performance, data were recorded on 50 individual plants from each line at maturity. Data on 12 different morphological characteristics of spikes and plants were collected. The range for plant height varies from 49.2 to 63.0 cm. Minimum of 65.8 g and maximum of 91.8 g plant dry weight were recorded. The lowest seed weight per plant was 6.39 g, and the highest was 9.17 g. The results indicate that highly valuable Salicornia can be grown successfully in arid regions using seawater for irrigation.

Germination and seedling of

Chenopodium quinoa

were evaluated under different salinity concentrations in the culture medium in order to introduce it in Morocco as a crop for the reclamation of saline soils under saline irrigation.

C

.

quinoa

seeds were treated with aqueous solutions of 0, 75, 100, 125 and 150 mM of NaCl (corresponding respectively to 0, 15, 20, 25 and 30% seawater concentration). The germination percentage was strongly affected by salinity such that only 45% seeds were germinated at 150 mM NaCl compared to the control that germinated at the rate of 80%. Five-week-old seedlings were irrigated with four seawater (SW) dilutions (20, 30, 40 and 50%) in comparison with control plants of the same age irrigated with freshwater. Maximum biomass was registered in 20% SW treatment, and the threshold salinity tolerance was observed in 30% SW treatment. The root-to-shoot ratio went up with the increase of salinity in the culture medium, while the relative growth rates (RGR) decreased significantly. Ionic analysis of vegetative organs and seeds revealed that Na

+

and K

+

concentrations increased in all organs tested, while Ca

2 +

concentration decreased significantly. The concentration of Mg

2+

was not affected by the presence of salt in the culture medium.

The possibility of inducing pea plants for better growth and yield in reclaimed soil with ECe (7.9 dS m

−1

) was investigated in a private farm in Fayoum, Egypt. The experiments were conducted during the two successive seasons of 2007/2008 and 2008/2009 using a soil classified at the family level as Typic Torriorthents, fine-loamy, mixed, and hyperthermic. The calcium paste-treated pea seeds were sown in beds fecundated with ground sunflower heads; the plants were sprayed with ascorbic acid at the rates of 100, 200, 300, and 400 mg L

−1

. Significant positive influences of calcium paste plus ground sunflower heads applied solely or in combination with all ascorbic acid treatments were observed on growth traits (plant height, number of branches plant

−1

, and shoot dry weight plant

−1

), some chemical components (leaf pigments, some photosynthates, Ca, Na, and Ca/Na ratio), and green yield of pods and seeds. As for ascorbic acid foliar application, all studied rates revealed significant increase in all aforementioned parameters with superiority of 300 mg L

−1

rate as compared to the control (water application). It has been concluded that spraying pea plants “cv. Master-B,” produced from calcium paste-treated seeds sown in beds fecundated with ground sunflower heads, with ascorbic acid at the rate of 300 mg L

−1

proved to be the best combined treatment and may overcome the adverse conditions of newly reclaimed soils particularly ECe of 7.9 dS m

−1

, and consequently, economic green yield of pods and seeds is obtainable.

Of 2.83 × 10

6

hectares (ha) coastal area of Bangladesh, about 1.0 × 10

6

ha is suffering from various levels of salinity. During monsoon, rice can be grown in these areas due to rainfall-induced natural leaching. In dry seasons, soil salinity increases in the soil profile and hence the entire coastal saline belt remains fallow. Considering this, International Center for Biosaline Agriculture jointly with Bangladesh Agricultural Research Institute initiated a project to grow cash and forage crops using irrigation and water management technologies in the coastal saline soils.

In 2007–2008, an initial pilot assessment was made and basic soil properties were determined in Satkhira District, where soil salinity (EC

e

11 dS m

−1

) was recorded in dry months (March–April). Tomato, cowpea, and barley were used as test crops and harvested rain water was used for irrigation. Tomato crop with drip irrigation on mulched raised beds produced 55–66 t ha

−1

yield, which is 3.13–3.36 times of control treatment (flat lands with traditional can irrigation). A net return of US$ 2,658–3,559 ha

−1

was obtained which is 5.76–5.92 times more than the control treatment. The hosepipe irrigation in mulched raised bed gives net return of US$ 2,696–3,610 ha

−1

, about 5.84–6.00 times more than the control treatment. These returns are higher than those obtained from drip irrigation due to less investment in irrigation setup. Fodder crops (i.e., cowpea and barley) were also found profitable. These were irrigated by both fresh and saline water using hosepipes with different irrigation scheduling. The net returns of cowpea and barley were about 4.00–4.23 and 2.11–2.60 times more than the control treatment, respectively, in various locations. The study indicates that 770,000 ha saline coastal land (EC

e

≤ 12.0 dS m

−1

) has the potential for crop and fodder cultivations through proper irrigation and soil management practices.

Most models about global changes predict the development of salt deserts with strongly degraded vegetation, unhealthy living conditions and negative impact on economic goods. The reservoir of freshwater on earth (especially in arid zones) is not sufficient to ensure the feeding of manhood in future. Furthermore, the substitution of freshwater against saline sources in combination with unprofessional artificial irrigation systems leads to an increasing destruction of useful areas and to strong economic damages. The consecutive increase of soil salinity is a threat for the productive land because most crops have only a low degree of salt resistance. In future, halophytes, plants with a natural high salt resistance, can play a major role for the rehabilitation and economic use of salt-affected habitats. Halophytic ecosystems present a high productivity and can be the base for a sustainable agriculture on saline soils.

A precondition is the extension of the up to now incoherent knowledge about the ecology of halophytes, their economic potential and – for the warranty of a sustainable use – also about their individual mechanisms of resistance. The physiological studies with the sea water irrigation system shown in this chapter have the potential to provide highly valuable means of detecting individual mechanisms of species against NaCl toxicity and may also provide opportunities for the comparison and screening of different varieties for their adaptation to salinity (QCS for cash crop halophytes). After the selection of halophytic species suited for a particular climate and for a particular utilisation, greenhouse experiments at the local substrates (and climatic conditions) to select and propagate promising sites have to be started.

Worldwide, initiatives are being undertaken to develop saline vegetable crops, as well as crops for fuel and fibre, but the use of halophytes is still in the early stages of development.

Considering the interest for arid and semi-arid regions to improve biosaline agriculture by domestication and sustainable use of halophytic plants in salt-affected regions, present work was accomplished by studying diverse ecophysiological mechanisms of several promising candidates such as

Batis maritima

,

Sporobolus spicatus

,

Spartina alterniflora

,

Sesuvium portulacastrum

,

Beta vulgaris

ssp.

maritima

and

vulgaris

and

Aster tripolium

. They all share high economic potential, the ability for reclamation of salt-affected lands and to survive at high salinities. Seawater was used as the source of saline water at different dilutions with fresh water: 0% (control: fresh water), 25, 50, 75 and 100% seawater. Plants were cultivated in an automated irrigation and drainage system, in coastal sand as substrate, under highly reproducible greenhouse conditions (

quick check system

). The salt-tolerant species survived at all salinity treatments, and maximum growth occurred in low and moderate salinities (25 and 50% seawater). Beyond the optimal growth treatment, a progressive growth decrease took place. Threshold of salinity tolerance differed from one species to another which is related to osmotic adjustment by the regulation of minerals and water uptake from culture medium. To avoid toxicity of excess ion accumulation, halophytic plants have developed morphological and anatomical adaptations at the scale of the whole plant. The Na

+

and Cl

−

were the dominant ions, and their concentrations increased with the increase of seawater concentrations while K

+

concentration decreased. However, the degree of NaCl – and the maintenance of K

+

content – accumulation differed between species. One similarity of all halophytes was the unaffected Ca

2+

uptake and transport through the plants when plants are irrigated with seawater which is rich in Ca

2+

.

To introduce

Avicennia marina

in some bays of Morocco, a planting test has been carried out in the bay of Agadir. The plantation failed mainly due to human pressure and natural stress (wind); however, these effects could have been reduced through taking necessary measures during the first stages of plantation. As a follow-up to this failure, and to better understand the optimum conditions for the establishment of

A. marina

under Moroccan conditions, several experiments are carried out; one of these was the vegetative propagation of the species and growth under different salinity levels. It is observed that air layering showed encouraging results, when 30% of plants produced thick roots after 5 months. The performance of 6-month-old

Avicennia marina

plants was evaluated in quick check system (QCS) using five water salinity levels (0, 50, 75, 100 and 150% seawater) and by studying limit of salt tolerance, growth and some physiological parameters. The number of leaves, length and area, stem diameter, branching and biomass showed a similar trend, that is, maximum values were obtained in 50% seawater. The threshold of salt tolerance exceeded 150%. Ions concentration (K

+

, Na

+

, Ca

2+

and Mg

2+

), relative water content (RWC), protein content and osmotic potential of different parts of the plants showed that

Avicennia marina

adapts physiologically to survive under very high salt stress conditions. Ions concentration increased with increasing salinity (0.59 g/100 g and 2.35 g/100 g of Na

+

at 0 and 150% seawater, respectively, in leaves), and their content in the shoots was higher than in the roots. In consequence, osmotic potential was lower in plants grown in high salinity (−12.24 bars at 0% and −37.45 bars at 150% seawater in roots).

Salt-affected lands in the Central Asian region demonstrate the most characteristic features of natural continental terrestrial salinization, sodication, and alkalinization. Low organic matter (<1.0%), high salt contents, and poor water-holding capacity render these soils unproductive. The predominant salinity type is sulfate-chloride. The Na

+

and

$ {\rm{SO}}_{4}^{2-}$

are dominant ions. Total nitrogen and phosphorus ranged between 0.7–5.5 mg kg

−1

and 10.0–18.26 mg kg

−1

, respectively. Available potassium is low or moderate. Vegetation richness, botanic species diversity, and plant biomass were well integrated with soil moisture and soil salinity. A linear regression equation between apparent soil electrical conductivity (EM38) and quantitative Na

+

accumulation for 0–75 cm (

r

2

 =  0.88) soil profiles allowed us to identify the proportional contribution and interactive effects of each plant community (calculated for C

3

/C

4

species abundance) at fine desert landscape scale. Foliar δ

13

C (carbon discrimination ) indexes as an indicator of long-term water-use efficiency in plants in a restored forest – pastures ecosystem showed that δ

13

C of C

3

species increased with a decrease in soil water availability, suggesting that water-use efficiency increased with decreasing soil moisture and salinity. The C

4

species’ occurrences were observed to be absent and/or scarce within relatively lower soil moisture microhabitats, whereas they occurred and/or even had a high abundance within relatively higher soil moisture microhabitats and salinity, suggesting limited moisture available was a key factor of limiting C

4

distribution in arid region. The suitable coexistence of C3/C4 into an integrated agroforestry – farming system comprising 12–15% of tree cover, 58% of alfalfa, and 27–30% of annual forage crops provides satisfactory drainage – control of these salt affected marginal lands preventing salts accumulation at the root zone area. Trees/shrub plantations were deeply planting (sticks tap into the water table) through seedlings transplanting in early spring or late autumn seasons. A limited irrigation with low-quality water has been applied during the initial stage of growth before sole reliance on available drainage water (EC 4.5–12.3 dS m

−1

) resource becomes possible. The most promising plants including stands of native rangeland halophytes grown alone, or mixed with various traditional salt-tolerant trees, and fodder crops are addressed in this chapter.

This chapter addresses various aspects of

Atriplex

cultivation (

Atriplex halimus

and

Atriplex nummularia

) from Egypt and Morocco. The species were analyzed for germination and growth under irrigation with different water salinity levels (5, 10, and 20 dS m

−1

) and freshwater as control. Germination experiments were conducted on filter paper and sterilized soils. Growth and development parameters were measured on plants growing in sandy soil. One set of 64 containers was flushed with saline water to start the experiment. The germination experiment was continued for 2 months. Germination percentage, plant height, number of shoots and lateral shoots, fresh and dry weight, leaf area, xylem water potential, and Na and Cl ion content in plants were recorded in germination tests. Soil salinity (EC) at various depths and Na and Cl ions in soil were determined. It has been found that the germinability of both species (fresh seeds) is correlated linearly to water EC; both species gave different quantitative responses to various treatments, and the best response was with non-freshwater treatment, indicating that plants showed a good potential of taking up salt from saline soil in the soil column. A strict correlation was contributing to the desalinization of the saline soil irrigated with freshwater that promptly leached the salinized soil, while irrigation with diluted seawater caused a progressive enrichment of salts in soil and subsequently in the leaves and xylem water potential. It is concluded that

Atriplex

can be profitably grown in saline environment where conventional plants cannot grow. However, more research is needed to explore many ecophysiological aspects as well as to assess the long-term sustainability of saline water irrigation.

Land degradation is a major global issue because of its adverse impact on agricultural productivity and sustainability. Population pressure along with the demand for more food, fodder, and fuelwood has generated a chain of interrelated economic, social, and environmental issues associated with the land degradation especially in developing countries in arid and semiarid regions. In this concern, two pot experiments were conducted in the greenhouse of the National Research Centre, Dokki, Giza, to study the mutual influence of soil salinity (five initial soil salinity levels, i.e., 2.84, 5.36, 10.22, 17.45, 20.56, and 24.69 dS m

−1

) referred as S

0

, S1, S

2

, S

3

, S

4

, and S

5

, respectively, on the growth, physiological aspects, and some cation content as well as biomass production of

Leptochloa fusca and Sporobolus virginicus

grasses. Moderate levels of initial soil salinity significantly increased most of the growth characters in both seasons. The S

2

and S

3

treatments for

Sporobolus virginicus

and S

3

and S

4

treatments for

Leptochloa fusca

gave the highest values for all growth characters and biomass production in the first and second seasons, respectively. The improvement of growth characters and biomass production of both species in the second season is due to improving the initial soil salinity. Meanwhile, leaf/stem ratio increased with increasing the initial soil salinity in both seasons. Increasing initial soil salinity significantly increased Na

+

, soluble carbohydrates, and proline concentration in the plant tissues. On the other hand K

+

, K

+

/Na

+

ratio, and Ca

2+

content insignificantly decreased with the same treatment compared to control. No clear effects were recorded for Mg

2+

. As for the effect of successive growing of

Leptochloa fusca

and

Sporobolus virginicus

on the soil quality is concerned, all cations, anions (except for

$$ {\text{HCO}}_{3}^{-}$$

), sodium adsorption ratio, and electrical conductivity decreased by the end of the first season and reached its lowest values by the end of the second season; this is due to the leaching and to the accumulation of salts as halophyte plants are capable of accumulating salts into their leaves’ vacuoles and excrete it through their salt glands.

Leptochloa fusca

had more pronouncing effects on improving soil quality more than

Sporobolus virginicus

.

A large area of Indian soils is of marginal quality with high pH and alkalinity especially in semiarid conditions. Such soils contain excessive sodium salts and possess impermeable hard pan of calcium carbonate below the soil which affects the survival of crops. Currently, these soils are reclaimed by using chemical amendments and mechanical means which exert higher costs, and this practice is repeated every year prior to sowing of crop. In India, per capita land is decreasing every year due to steep rise in population which requires more food to fulfil their requirements. The land is limiting factor. The only way to increase land is through reclamation of abandoned saline and sodic lands and their use for crop production. Permanent reclamation of alkaline soils (high pH) is possible by the adoption of agroforestry system in which trees and crops are grown together which sustain agricultural production and productivity. Keeping in view the seriousness of the problem, an experiment was conducted to improve soil characteristics through agroforestry system for Central Plain Zone of Uttar Pradesh, India. The project was undertaken during the year 1989–2002, at Chandra Shekhar Azad University of Agriculture and Technology, Kanpur, Uttar Pradesh, India. The key objective of the experiment was the selection of suitable multipurpose trees which can improve soil quality of high pH (alkaline soils) for crop. The experiment consists of ten multipurpose tree species, namely,

Azadirachta indica, Dalbergia sissoo, Albizia procera, Terminalia arjuna, Eucalyptus hybrid, Leucaena leucocephala, Acacia nilotica, Acacia catechu, Morus alba and Cassia siamea

, and in between two rows of trees, agricultural crops were planted. The initial average soil pH, organic carbon and electric conductivity were 10.5, 0.41% and 0.73 dS m

−1

, respectively. After 12 years experimentation, it was concluded that the planting of multipurpose trees improved the soil organic carbon up to 0.59% and reduced the soil pH up to 8.10 and EC 0.31 dS m

−1

. The agricultural crops, namely, rice in Kharif (rainy season) and wheat in Rabi (winter season), were found suitable with trees. Among the trees, Eucalyptus hybrid reduces the soil pH and EC drastically as compared to other trees, whereas higher carbon was estimated with

Leucaena leucocephala

followed by Dalbergia sissoo,

Acacia nilotica and Morus alba

.

Accumulation of salts on soil surface and in the root zone damages physico-chemical and biological properties of salt-affected soils. Exo-polysaccharides (EPS), the polymers of monosaccharides, are synthesised and released in soil by microorganisms inhabiting rhizosphere, roots of the plants and the decomposing organic residues. The bacterial EPS are involved in formation and stability of soil micro-aggregates, a factor that ensures fertility of the cultivated soils. The rhizosheaths formed around roots by bacterial EPS contribute to build up soil physical structures, regulate nutrients and water flow from rhizosphere soil to the plants, promote growth and protect the roots against pathogens. Thus, the bacterial EPS are directly and indirectly involved in and impacted both physico-chemical soil characteristics and growth of the plants. However, the role of the bacterial EPS in improving soil fertility and interaction with constituents of the salt-affected soils has rarely been explored. Research studies, therefore, were conducted to observe the effect of the bacterial EPS extracted from

Microbacterium

sp. MAS133 isolated from a salt-affected soil on soil moisture release and aggregate stability at three (native, acidic and alkaline) pH values of clay fraction of a saline-sodic soil compared to a normal soil. Results showed that the processes and phenomenon of soil aggregate formation and stability in the colloidal form with interactive effect of biopolymers and SMA (suspended micro-aggregates) as well as water retention and release of a saline-sodic soil were all influenced by the bacterial EPS. Although extent and nature of the bacterial EPS-micro-aggregates interactions varied with pH, soil type and EPS concentration, the effect was consistent and persistent for extended time periods. Moreover, 16S rRNA gene sequence analysis showed that MAS133 belonged to

Microbacterium hominis

of the lineage of the Firmicutes and the EPS produced on sucrose medium were fructose biopolymers. Interaction of the bacterial biopolymer with soil constituents and a positive impact of the bacterial inoculation on soil aggregation around roots and mitigation of negative effects of salinity on plant growth observed in earlier studies suggest the EPS-producing bacteria a useful biological tool for reclamation of the salt-affected soils. Additionally, a strategy of provision of carbohydrate substrates to foster growth and production of the EPS by the bacterial populations living in the salt-affected soils through field water distributaries and the ‘bioretention’ or ‘biomonitoring’ cells could help overcome the economy and the environmental concerns associated with application and use of the bacterial inoculum in the field.

Egypt is facing several fundamental problems: an ever-increasing population, a limited supply of cultivable land, and a limited supply of water resources. These problems intensify the importance of developing efficient natural resource use strategies. The future of Egypt depends on the water stored in the Nasser Lake reservoir for all purposes. There is strong evidence that governmental policies in the agricultural sector have led to an inefficient allocation of resources in general and water resources in particular, the latter being the focus of this study. These policies should be examined within sound economic frameworks, and policy alternatives should be tested to insure the efficient use of water resources. The last drought in Africa brought attention to the need for optimal intertemporal allocation of this vital resource. There are three major marginal-quality water sources that can be used in Egypt: wastewater, saline, and sodic agricultural drainage water and brackish groundwater. At present, wastewater is reused in many areas sometimes after dilution but mostly without enough treatment. Also, farmers use saline-sodic drainage waters in areas which suffer from irrigation water shortage especially at the end of irrigation canals. Still others irrigate with saline or brackish groundwater, either exclusively or in conjunction with good quality surface water. Many of those farmers cannot control the volume or quality of water they receive. Wastewater often contains a variety of pollutants: salts, metals, metalloids, pathogens, residual drugs, organic compounds, endocrine disruptor compounds, and active residues of personal care products. Any of these components can harm human health and the environment. Farmers can suffer from harmful health effects after contacting with wastewater, while consumers are at risk from eating vegetables and cereals irrigated with wastewater. Application of wastewater has to be carefully managed for effective use. In this chapter, the challenges and opportunities of marginal water use in Egypt are discussed. This chapter focuses on the marginal water use considerations technically (including space, time, quantity, and quality), economically, environmentally (including northern lake ecology, Delta salt balance and pollution concentration, and health risks), socially (including acceptance and practice), legally, and institutionally.

Sub-Saharan Africa accounts for 25% of the global figure of chronically undernourished. The region simply does not produce enough food to adequately feed its population, and food production per capita is declining. If nothing changes in sub-Saharan Africa (SSA), the absolute numbers of poor in the region will continue to increase. Unless African governments, supported by the international community, take the lead in confronting the factors that cause nutrient depletion and land degradation, deteriorating agricultural productivity will seriously undermine efforts to bring about food security and to strengthen the foundations of sustainable economic growth in SSA.

This chapter reviews the current state of knowledge related to the condition of SSA land and water resources and highlights the importance of linking degraded land and water management at local and landscape scales in order to address pressing issues of food crisis in the region. There has been less agricultural water development to date in SSA than in any other region. Water management is usually the key to increasing the productivity of arid and semiarid lands. The dominant water resource management challenge over the coming generations is how to secure water to cover food demands of a rapidly expanding population. Promising technologies available to farmers in SSA include conservation tillage, rainwater harvesting, and integrated soil and water conservation. Intensifying agricultural production has in the past often been carried out with negative side effects in terms of land and water degradation. Therefore, legislation that will safeguard a water reserve and efficient water productivity improvements that will make it the region to achieve the Millennium Development Goals (MDGs) and thus long-term sustainability in agricultural productivity is recommended.

Waters of Medjerda wadi catchment (eastern Algeria) are one of the most important resources in Algeria. In this basin, waters are used for irrigation purposes. However, they collect domestic and industrial sewages and irrigation effluents exposing surface and groundwater to significant pollution. In this study water quality monitoring in Medjerda wadi has been completed. Longitudinal profiles of water quality were completed using the data from 14 sites. All sewages from agricultural and industrial discharges were included. The water samples were analysed for nutrients (

$$ {\rm{NO}}_{3}^{\\-}$$

,

$$ {\rm{NO}}_{2}^{\\-}$$

,

$$ {\rm{NH}}_{4}^{\\+}$$

and

$$ {\rm{PO}}_{4}^{\\3-}$$

), biochemical oxygen demand (BOD

5

) after 5 days and dissolved oxygen (DO). Chemical composition showed the waters in the Medjerda wadi are extremely polluted, especially, at the confluence with domestic releases of Souk Ahras city and downstream of industrial discharges and therefore present a serious risk for irrigation. This pollution is characterized by an increase in indicators of pollution (BOD

5

,

$$ {\rm{NO}}_{2}^{\\-}$$

,

$$ {\rm{NO}}_{2}^{\\-}$$

,

$$ {\rm{NH}}_{4}^{\\+}$$

and

$$ {\rm{PO}}_{4}^{\\3-}$$

), a very low rate of dissolved oxygen and high concentrations of heavy metals particularly iron.

Entisols are common soils in the arid regions and have the potential for irrigated agriculture. However, when these soils are irrigated with brackish/saline water and the irrigation is poorly managed, the soils become saline. Maintaining desired saltwater balance in the potential root zone area is the key factor for growing agricultural, forestry, and landscaping plants under saline soil and water conditions. Irrigation management is one of the practices that can assist in achieving such a goal. In fact, irrigation methods along with better scheduling can manage the wetting-front movement and salt accumulation in the root zone. Micro-irrigation methods are usually desirable under water scarcity/salinity situations to facilitate water conservation and managing soil salinity. Among these irrigation systems, the trickle is commonly used for efficient soil salinity management and irrigation. In order to verify the above, field experiments on three emitter spacing (25, 50, and 75 cm) in two layout patterns (square and triangle) were evaluated on Entisols at the experimental farm of Dubai-based International Center for Biosaline Agriculture. Soil samples were collected at 0–25- and 25–50-cm depths and analyzed for EC of soil saturation extract to assess soil salinity development around the emitters. Results show that triangle pattern of emitters minimizes soil salinity development compared to salinity development in the square-type pattern through overlapping of wetting fronts and subsequent leaching. Similarly, close spacing of emitters also overlaps wetting fronts, and that helps in reducing salt accumulation. These preliminary findings may help formulate suitable irrigation management practices for growing different plants under saline environments.

Salinity is one of the most severe environmental factors limiting the productivity of agricultural crops. In this chapter, evaluation of water quality of Mouillah wadi was carried out in order to assess its suitability for irrigation purposes. Mouillah wadi is a subbasin of Tafna watershed which is situated in the north-west of Algeria. It feeds the Hammam Boughrara dam with a capacity of 177 Mm

3

. This wadi has important sources of pollution contaminating water whose quality deterioration is a direct consequence of the discharge of the effluents of all categories in surface water (industrial and urban wastes). To evaluate the water quality, chemical parameters such as the residual sodium carbonate (RSC), the magnesium hazard (MH) and the permeability index (PI) using US Salinity Laboratory Staff salinity classification and the Wilcox diagram were determined, and seasonal variation diagrams were prepared. The electrical conductivity values show the dam waters to be of marginal quality. The waters of Mouillah wadi are of poor to harmful quality according to Wilcox classification. The calculated values of SAR and % Na plotted on SAR and Wilcox diagrams versus conductivity indicate a good to doubtful use of the dam water for irrigation. High salinity, % Na, Mg hazard and RSC values at Mouillah wadi limit the use for agricultural purposes.

In Egypt, saline-sodic clayey soils represent approximately 109,200 ha of the delta. At present these areas are either of poor or low quality mainly due to salinity and sodicity problems. In Tina Plain area of North Sinai, there are about 6,300 ha of problematic saline-sodic clayey soils. Tina Plain area of North Sinai is one of the three regions of the reclamation areas under El-Salam canal development project. It represents the first region of the project. This project envisages the reclamation of an area of 170,000 ha. Therefore, it is important to measure the water use efficiency for leaching saline-sodic clayey soils in this area using irrigation water from El-Salam canal to evaluate the agro-economic value of this project. The study was conducted in an experimental field of saline-sodic clayey soils in Tina Plain area. The experimental field has an actual area of 25 ha. The soil is saline with heavy clay texture, poor drainage, shallow groundwater tables and 30-cm surface salt layer. From the site characteristics it is realistic that the most appropriate strategy for this stage of reclamation is to apply intermittent leaching and surface drainage. This strategy succeeded to remove the salt layer within 6 months of leaching. The study was extended for 1 year. The results indicated that 2.9 t of salts were leached for each hectare per day with irrigation water quantity of 223 m

3

. The average soil salinity before leaching was 400 dS m

−1

(0–50 cm) and 300 dS m

−1

(50–150 cm). Leaching decreased the soil salinity at the surface layer to about 100 dS m

−1

with leaching efficiency of 75%. For the other layer, EC decreased to 150 dS m

−1

with leaching efficiency of 50%. The water table depth below ground surface was lowered from 0.16 m to about 0.86 m below ground surface. This indicates that the soil properties also improved due to the salt leaching process.

The objective of the present study was to investigate the potential of some plants to uptake and accumulate some essential elements and cadmium in soils under wastewater irrigation. The study was performed in the farmer’s field in 2005 at Varamin region located in the south of Tehran, Iran. The soil at the studied site belongs to Shahr-e-Ray Series and soil taxa “

Fluventic Camborthids

”. The sunflower, turnip and forage corn were selected for the investigation. The wastewater was used for irrigation purpose. The experiment was laid out in a randomized block design (RBD), and treatments were triplicated. The sunflower, turnip and forage corn plants were harvested in 2005, and the plants were separated into roots and aboveground material. The results showed the highest concentration of nitrogen, phosphorus, zinc, copper and cadmium was 6.05%, 1.27%, and 97.27, 22.84 and 0.54 mg kg

−1

in sunflower, respectively, and the most accumulations of nitrogen, phosphorus, zinc and copper were in grain and cadmium in the leaf. The concentration of potassium and nitrate was 5.79 and 8.26% in turnip, respectively, and the high accumulation of potassium and nitrate was in leaf. The highest concentration of iron and manganese was 349.56 and 144.78 mg kg

−1

, respectively, in forage corn. The results suggest that the lands irrigated with wastewater with excessive amount of essential elements and cadmium can support sunflower cultivation through uptake of sufficient quantities by selected crops.

The use of natural resources to meet people’s requirements, currently and in the future, is sustainable agriculture. In order to uphold the growing rural and urban population in the developing world, considerable development in the efficiency of agricultural systems is required. Intensification of current production systems via increasing cropping intensity and by increased use of external inputs is often the only way to increase agricultural production. However, a major portion of the currently cultivated land is being lost through soil degradation. Degradation includes soil erosion, nutrient depletion, desertification, deforestation, salinization and overgrazing. As agricultural areas become even more crowded, arable land has come under increasing pressure. Agricultural yields are at risk of serious decline as soils are becoming more degraded, putting the livelihoods of millions of subsistence farmers at risk. Integrated soil fertility management (ISFM) is the key in raising productivity levels while maintaining the natural resource base. The main purpose of this integrated approach is to restore soil nutrient pools, maximize on-farm recycling of nutrients, reduce nutrient losses to the environment and improve the efficiency of inputs. Soil fertility can be built up by progressive and steady modification of the natural resources including soils, vegetation and water by crop fallowing, grazing, selecting crop species, deep ploughing to break the plough pan, subsoiling, organic fertilizing, transferring crop residues and fodder. Therefore, ISFM is a viable tool to rebuild the degraded soils. Conclusively, ISFM can play a major role in improving farm output from degraded lands and ultimately in ­sustainable agriculture for the poor farmers.

To help bridge the gap between food demand and supply, Pakistan requires an optimum, sustainable, and best adopted strategies to maintain the momentum of the agriculture sector. Investments need to be made in agricultural education, research and development, extension, soil and water resources, and allied infrastructural development which will lead to increase the food production and improve soil and water conservation. Wheat-rice cropping system in Pakistan, particularly in the areas where late-maturing fine-rice varieties are grown, the late-season harvesting of rice crop coupled with conventional land preparation leads to significant delay in wheat sowing and extra usage of irrigation water, and preparatory tillage operations result in a reduction in wheat yields. These practices not only increase the costs of production but also degrade the soil structure and organic matter availability. Conservation tillage technology including earlier wheat plantation, improved water use efficiency which can help to resolve this yield decline when compared with conventional tillage practices in both canal and ground water command areas. In an attempt to test these technologies, a comparative study on the soil and water conservation is tested using four wheat varieties in randomized complete block design (RCBD). Analysis revealed significant differences in all noted parameters including yield-contributing traits due to conservation tillage system compared to where this was not used. It was concluded that out of four exotic and local wheat varieties, the genotype Inqalab-91 proved best yielder in seedling as well as across tillage operation conditions. Additionally, the energy conservation was also done by adopting an integrated, holistic, and pragmatic approach to ensure staple food ­especially in competitive areas of semiarid regions.

To rehabilitate the degraded soils and to improve the quality of ­agricultural product, especially leguminous plants (

Vicia faba

L.), we used bentonite to ameliorate the physical and chemical properties of sandy soil. To evaluate the ecological advantage of bentonite, we studied the effect of increasing amounts of bentonite on the physical and chemical characteristics of analyzing pH, EC (electrical conductivity), total calcareous, active calcareous, total phosphorus, organic carbon, organic matter, total nitrogen, and cation-exchange capacity. In Algeria, the drought has increased salts in the rhizosphere in the soils of semiarid and arid areas. The objective of this study was to assess the response of leguminous plants (

Vicia faba

L.) to increasing levels of salts, the combined effect of bentonite/salts to certain metabolic activities, mineral contents, and morphophysiological behavior of the plant response to abiotic stress. It is observed that variability exists in the physical and chemical characteristics and morphological growth of the plant according to the bentonite amount mixed in the sandy soil sample.