ReviewCrop and irrigation management strategies for saline-sodic soils and waters aimed at environmentally sustainable agriculture
Introduction
Irrigation has ever been an important factor in agricultural development. The area of land under irrigation in the world has expanded substantially, particularly in the second half of the last century. Between the mid-1960s and the mid-1980s, expansion of irrigation has accounted for more than 50% increase in global food production (El-Ashry and Duda, 1999). Although only approximately 17% of the world's cropland is irrigated, it produces more than a third of the food and fiber harvested throughout the world (Hillel, 2000). The expansion in irrigated agriculture needs to continue as the world population increases, but annual renewable freshwater resources for the foreseeable future are now largely allocated. There may be some areas where freshwater resources increase or decrease according to rainfall changes due to climate change, however, these are likely to occur at the level that is small compared to the increased future demands for freshwater (Wallace, 2000). Competition for freshwater already exists among the municipal, industrial and agricultural sectors in several regions due to an increase in population. The consequence has been a decreased allocation of freshwater to agriculture (Tilman et al., 2002). This phenomenon is expected to continue and to intensify in less developed, arid region countries that already have high population growth rates and suffer from serious environmental problems.
As supplies of good-quality irrigation water are expected to decrease, available water supplies need to be used more efficiently (Oweis et al., 1999, Hatfield et al., 2001, Wichelns, 2002), where one of the techniques can be the reuse of saline and/or sodic drainage waters generated by irrigated agriculture (Shalhevet, 1994, Rhoades, 1999, Oster, 2000), or of marginal-quality waters generated by municipalities (Bond, 1998, Bouwer, 2002). The same applies to salt-affected soils, which occupy more than 20% of the irrigated lands (Ghassemi et al., 1995), and warrant attention for efficient, inexpensive and environmentally acceptable reclamation and management to improve crop production (Qadir and Oster, 2002). If mismanaged, the use of such poorer quality waters and soils can increase salinity and sodicity problems, which already plague many irrigation projects reducing crop yields.
A major problem with irrigated agriculture is its negative environmental impacts. Irrigated agriculture, over the long-term, cannot avoid causing adverse off-site effects due to the drainage water it generates (Van Schilfgaarde, 1994). The generation of drainage water by irrigation is a necessity to maintain soil salinity, through leaching, at acceptable levels for crop growth. However, it is no longer sufficient to set leaching requirement objectives based solely on irrigation water salinity and crop salt tolerance. Nor is it sufficient to limit the objectives of soil reclamation, or rehabilitation, to reducing soil salinity and sodicity to levels that permit high levels of crop productivity. The environmental impacts of the drainage waters generated by reclamation, rehabilitation and irrigation in general must also be considered. What is the disposal site for the drainage water, or more to the point, the salt it contains? What will be the impact on the chemical composition of the receiving waters or soil strata? The key issues are: (1) What can be done to minimize the volume of drainage water? (2) Should the disposal of unusable drainage water be localized to the sub-regions where these waters are generated. One strategy to deal with such issues is to improve irrigation management (Wichelns, 2002) so that excess water is not applied over that needed for evapotranspiration and leaching. Another is to reuse drainage waters for irrigation of appropriate salt-tolerant crops (Rhoades, 1999).
In the future, sustainable irrigation systems using saline-sodic soils and waters have the potential to improve crop production with minimized adverse environmental effects. This will require a comprehensive approach to soil, water and crop management. The foci will need to be on reclamation of new lands, rehabilitation of saline and sodic lands generated by past irrigation practices, improved productivity per unit of water, and environmental protection. Crop and water management will play key roles in such a comprehensive approach, and are the foci of this review.
Section snippets
Vegetative bioremediation of sodic and saline-sodic soils
Accumulation of salts and sodium (Na+) in salt-affected soils originates either through the weathering of parent minerals (causing fossil or primary salinity/sodicity) or from anthropogenic activities involving the inappropriate management of land and water resources (contributing to man-made or secondary salinity/sodicity). Excess salinity levels do not have adverse impacts on soil structure and its physical and hydraulic properties. Rather, saline conditions may have favorable effects on soil
Reusing drainage waters for irrigation
Drainage from irrigated lands is a necessity for irrigation to be sustainable. Drainage waters carry a salt load that is always higher, sometimes substantially higher, than that of the irrigation water. In many instances, drainage water does not flow directly back to the rivers from which the irrigation water was obtained. Saline geologic deposits and saline groundwaters often exist along the flow path. As drainage water flows through these deposits, or displaces the saline groundwater, the
Crops for vegetative bioremediation and drainage water reuse strategies
An appropriate selection of plant species capable of producing adequate biomass is vital during vegetative bioremediation and different drainage water reuse strategies. Such selection is generally based on the ability of a crop to withstand elevated levels of soil salinity and sodicity while also providing a saleable product or one that can be used on-farm. Salinity may reduce crop yields by disturbing the water and nutritional balance of plants (Maas and Grattan, 1999). Sodicity affects plant
Future perspective
Despite limitations with the freshwater supplies, particularly in water-starved countries, there will be an increasing need for more water to meet the needs of municipal, industrial and agricultural sectors. With increasing population, less and less freshwater will be available for agricultural use. Consequently, the use and reuse of saline and/or sodic irrigation waters is expected to increase in the future. This scenario generates a need to modify existing soil and crop management practices
References (102)
Restoration of saline land through revegetation
Agric Water Manage
(2002)Role of natural vegetation in improving salt affected soil in northern Egypt
Soil Till Res
(2002)- et al.
Bio-reclamation of saline-sodic soil by Amshot grass in northern Egypt
Soil Till Res
(1992) How do plant roots acquire mineral nutrients? Chemical processes involved in the rhizosphere
Adv Agron
(1998)- et al.
Chemical changes in a saline-sodic soil after gypsum application and cropping
Soil Technol
(1997) - et al.
Biomass production and soil amelioration in a high density Terminalia Arjuna plantation on sodic soils
Biomass Bioenerg
(1998) Saline water management for irrigation in India
Agric Water Manage
(1996)- et al.
Irrigation with saline water in the reclaimed marsh soils of south-west Spain: impact on soil properties and cotton and sugar beet crops
Agric Water Manage
(2001) Irrigation with poor quality water
Agric Water Manage
(1994)The chemistry of submerged soils
Adv Agron
(1972)
Reclamation of a saline-sodic soil by gypsum and Leptochloa fusca
Geoderma
Use of saline-sodic waters through phytoremediation of calcareous saline-sodic soils
Agric Water Manage
Intercepting, isolating and reusing drainage waters for irrigation to conserve water and protect water quality
Agric Water Manage
Using water of marginal quality for crop production: major issues
Agric Water Manage
Strategy for long term use of saline drainage water for irrigation in semi-arid regions
Soil Till Res
Screening for salinity and waterlogging tolerance in five Casuarina species
Landscape Urban Plan
Increasing agricultural water use efficiency to meet future food production
Agric Ecosyst Environ
Amelioration of a calcareous saline-sodic soil by gypsum and forage plants
Land Degrad Rehabil
Salt tolerance of Echinochloa crusgalli
Biol Plant
Field crop production in areas with saline soils and shallow saline groundwater in the San Joaquin Valley of California
Microbiological and chemical amelioration of alkaline soil by growing Karnal grass and gypsum application
Exp Agric
Reclaiming sodic soils for wheat production by Prosopis juliflora (Swartz) DC afforestation in India
Agroforestry Systems
Effluent irrigation—an environmental challenge for soil science
Aust J Soil Res
Integrated water management for the 21st century: problems and solutions
J Irrig Drain Eng
Agroforestry farming system for the management of selenium and salt on irrigated farmland
Economics and effectiveness of biological and chemical methods in soil reclamation
Pak J Agric Res
Subsoil amelioration by plant roots—the process and the evidence
Aust J Soil Res
Optimal ratios of saline and non-saline waters for crop production
Soil Sci Soc Am J
Plant injury and adaptation to oxygen deficiency in the root environment: a review
Plant Soil
Future perspectives on agricultural drainage
Controlling dryland salinity by planting trees in the best hydrogeological setting
Land Degrad Dev
Salt tolerance of safflower
Agron J
Effect of salinity on grain yield, and quality, vegetative growth, and germination of triticale
Agron J
Kochia: a new alternative for forage under high salinity conditions of Mexico
Interaction of tree crops with a sodic soil environment: potential for rehabilitation of degraded environments
Land Degrad Dev
Using brackish water on normal and salt-affected soils in Pakistan: a review
Pak J Agric Sci
Salt tolerance and crop potential of halophytes
Crit Rev Plant Sci
Purslane (Portulaca oleracea L.): a halophytic crop for drainage water reuse systems
Plant Soil
Managing soils to achieve greater water use efficiency: a review
Agron J
Hydraulic conductivity of saline-sodic soil after gypsum application and cropping
Soil Sci. Soc. Am. J.
Comparison of biological and chemical methods for reclaiming saline-sodic soils
Pak J Sci Res
Bioamelioration of a sodic soil by silvopastoral systems in northwestern India
Agroforest Syst
The reclamation of alkali soils
Calif Agric Exp Sta Bull
Principles governing the reclamation of alkali soils
Hilgardia
Effect of saline water on soil properties and crop yield
Hassadeh
Economics of salinity and drainage management in irrigated agriculture
Cited by (403)
A geospatial assessment of soil properties to identify the potential for crop rotation in rice systems
2024, Agriculture, Ecosystems and EnvironmentImpacts of long-term saline water irrigation on soil properties and crop yields under maize-wheat crop rotation
2023, Agricultural Water ManagementField-scale measurements of soil physico-chemical profiles of the Potohar region in the Indus basin of Pakistan
2024, Irrigation and Drainage