How can salinity be managed

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We are like minded people, who stive to increase yields and save fertilizations costs, while being environmentally friendly! Are you sure you want to leave? Subscribe No, Thanks. Leaching every year may be eliminated by growing salt sensitive crops early in the crop rotation following leaching.

As salt accumulates, more salt-tolerant crops are grown. Leaching is performed following the last crop in the rotation. Crop rotation example are:.

Where shallow water tables limit the use of leaching, artificial drainage may be needed. Cut drainage ditches in fields below the water table level to channel away drainage water and allow the salts to leach out. Drainage tile or plastic drainpipe can also be buried in fields for this purpose.

With all artificial drainage systems you must also consider disposal of the drainage water. Restrictions on the discharge of drain water to streams may apply in certain situations and should be investigated through the Colorado Department of Public Health and Environment. In the case of regulated discharge, treatment or collection and evaporation of the water on site may be required and may add significant costs.

The advantage of artificial drainage is that it provides the ability to use high quality, low salinity irrigation water if available to a grower to completely remove salts from the soil. However, artificial drainage systems will not work where there is no saturated condition in the soil. Water will not collect in a drain if the soil around it is not saturated.

After drainage appears adequate, the leaching process can begin. The following equations can be used to estimate how much water is required to leach salts for reclamation purposes.

This equation can be used to estimate the depth of water to apply for simple continuous ponding with one application of water. With intermittent ponding, several small applications are applied.

Using several small applications requires less water than one single application. See the UC Davis publication cited below for additional guidelines on using this equation for reclamation leaching.

In addition to leaching salt below the root zone, salts can also be moved to areas away from the primary root zone with certain crop bedding and surface irrigation systems. Figures 1 and 2 illustrate several ways to manage salt accumulation in this manner. The goal is to ensure the zones of salt accumulation stay away from germinating seeds and plant roots. Irrigation uniformity is essential with this method.

Without uniform distribution of water, salts will build up in areas where the germinating seeds and seedling plants will experience growth reduction and possibly death. Double-row bed systems require uniform wetting toward the middle of the bed. This leaves the sides and shoulders of the bed relatively free from injurious levels of salinity.

Without uniform applications of water one furrow receiving more or less than another , salts accumulate closer to one side of the bed. Periodic leaching of salts down from the soil surface and below the root zone may still be required to ensure the beds are not eventually salted out. Alternate furrow irrigation may be desired for single-row bed systems. This is accomplished by irrigating every other furrow and leaving alternating furrows dry.

Salts are pushed across the bed from the irrigated side of the furrow to the dry side. Care is needed to ensure enough water is applied to wet all the way across the bed to prevent build up in the planted area. This method of salinity management can still result in plant injury if large amounts of natural rainfall fill the normally dry furrows and push salts back across the bed toward the plants.

This phenomenon also occurs if the normally dry furrows are accidentally irrigated. Crop residue at the soil surface reduces evaporative water losses, thereby limiting the upward movement of salt from shallow, saline groundwater into the root zone.

Evaporation and thus, salt accumulation, tends to be greater in bare soils. Fields need to have 30 percent to 50 percent residue cover to significantly reduce evaporation. Under crop residue, soils remain wetter, allowing fall or winter precipitation to be more effective in leaching salts, particularly from the surface soil layers where damage to crop seedlings is most likely to occur. Plastic mulches used with drip irrigation effectively reduce salt concentration from evaporation.

Sub-surface drip irrigation pushes salts to the edge of the soil wetting front, reducing harmful effects on seedlings and plant roots. As mentioned before, most crop plants are more susceptible to salt injury during germination or in the early seedling stages. An early-season application of good quality water, designed to fill the root zone and leach salts from the upper 6 to 12 inches of soil, may provide good enough conditions for the crop to grow through its most injury-prone stages.

Salts are most efficiently leached from the soil profile under higher frequency irrigation shorter irrigation intervals. Keeping soil moisture levels higher between irrigation events effectively dilutes salt concentrations in the root zone, thereby reducing the salinity hazard.

Most surface irrigation systems flood or furrow systems cannot be controlled to apply less than 3 or 4 inches of water per application and are not generally suited to this method of salinity control.

Sprinkler systems, particularly center-pivot and linear-move systems configured with low energy precision application LEPA nozzle packages or properly spaced drop nozzles, and drip irrigation systems provide the best control to allow this type of salinity management. Under irrigated conditions in arid and semi-arid climates, the build-up of salinity in soils is inevitable. The severity and rapidity of build-up depends on a number of interacting factors such as the amount of dissolved salt in the irrigation water and the local climate.

However, with proper management of soil moisture, irrigation system uniformity and efficiency, local drainage, and the right choice of crops, soil salinity can be managed to prolong field productivity. Using the salt-tolerant crops is one of the most important strategies to solve the problem of salinity. Salt tolerance in crops will also allow the more effective use of poor quality irrigation water. To increase the plant salt-tolerance, there is a need for understanding the mechanisms of salt limitation on plant growth and the mechanism of salt tolerance at the whole-plant, organelle, and molecular levels.

Under saline conditions, there is a change in the pattern of gene expression, and both qualitative and quantitative changes in protein synthesis. Although it is generally agreed that salt stress brings about quantitative changes in protein synthesis, there is some controversy as to whether salinity activates specialized genes that are involved in salt stress. Salt tolerance does not appear to be conferred by unique gene s Manchanda and Garg, When a plant is subjected to abiotic stress, a number of genes are turned on, resulting in increased levels of several metabolites and proteins, some of which may be responsible for conferring a certain degree of protection to these stresses Bhatnagar-Mathur et al.

Efforts to improve crop performance by transgenic approach under environmental stresses have not been that fruitful because the fundamental mechanisms of stress tolerance in plants remain to be completely understood. Development of salt-tolerant crops has been a major objective of plant breeding programs for decades in order to maintain crop productivity in semiarid and saline lands.

Although several salt-tolerant varieties have been released, the overall progress of traditional breeding has been slow and has not been successful as only few major determinant genetic traits of salt tolerance have been identified Schubert et al. Although there has been some success with technical solutions to the problem, the biological solutions have been more difficult to develop because a pre-requisite for the development of salt tolerant crops is the identification of key genetic determinants of stress tolerance.

The existence of salt-tolerant plants halophytes and differences in salt tolerance between genotypes within salt-sensitive plant species glycophytes indicates that there is a genetic basis to salt response Yamaguchi and Blumwald, Although a lot of approaches have been done for development of salt tolerant plants by transgenics complete success is not achieved yet.

The assessment of salt tolerance in transgenic experiments has been mostly carried out using a limited number of seedlings or mature plants in laboratory experiments. In most of the cases, the experiments were carried out in greenhouse conditions where the plants were not exposed to those conditions that prevail in high-salinity soils e. The salt tolerance of the plants in the field needs to be evaluated and, more importantly, salt tolerance needs to be evaluated as a function of yield.

The evaluation of field performance under salt stress is difficult because of the variability of salt levels in field conditions Richards, and the potential for interactions with other environmental factors, including soil fertility, temperature, light intensity and water loss due to transpiration.

Evaluating tolerance is also made more complex because of variation in sensitivity to salt during the life cycle. For example, in rice, grain yield is much more affected by salinity than in vegetative growth Khatun and Flowers, In tomato, the ability of the plants to germinate under conditions of high salinity is not always correlated with the ability of the plant to grow under salt stress because both are controlled by different mechanisms Foolad and Lin, , although some genotypes might display similar tolerance at germination and during vegetative growth Foolad and Chen, Therefore, the assessment of stress tolerance in the laboratory often has little correlation to tolerance in the field.

Although there have been many successes in developing stress-tolerant transgenics in model plants such as tobacco, Arabidopsis or rice Grover et al. There are several technical and financial challenges associated with transforming many of the crop plants, particularly the monocots. First, transformation of any monocot other than rice is still not routine and to develop a series of independent homozygous lines is costly, both in terms of money and time.

Second, the stress tolerance screens will need to include a field component because many of the stress tolerance assays used by basic researchers involve using nutrient-rich media which in some cases include sucrose. This type of screen is unlikely to have a relationship to field performance.

Third, because saline soils are often complex and can include NaCl, CaCl 2 , CaSO 4 , Na 2 SO 4 , high boron concentrations and alkaline pH, plants that show particular promise will eventually have to be tested in all these environments Joseph and Jini, Several strategies have been developed in order to decrease the toxic effects caused by high salinity on plant growth, including plant genetic engineering Wang et al. The role of microorganisms in plant growth promotion, nutrient management and disease control is well known and well established.

Previous studies suggest that utilization of PGPB has become a promising alternative to alleviate plant stress caused by salinity Yao et al. PGPR facilitate plant growth indirectly by reducing plant pathogens, or directly by facilitating the nutrient uptake through phytohormone production e. It has been demonstrated that inoculations with AM arbuscular mycorrhizal fungi improves plant growth under salt stress Cho et al.

Kohler et al. The plants inoculated with P. Bacteria isolated from different stressed habitats possess stress tolerance capacity along with the plant growth-promoting traits and therefore are potential candidates for seed bacterization.

When inoculated with these isolates, plants show enhanced root and shoot length, biomass, and biochemical levels such as chlorophyll, carotenoids, and protein Tiwari et al. Investigations on interaction of PGPR with other microbes and their effect on the physiological response of crop plants under different soil salinity regimes are still in incipient stage. Inoculations with selected PGPR and other microbes could serve as the potential tool for alleviating salinity stress in salt sensitive crops.

Therefore, an extensive investigation is needed in this area, and the use of PGPR and other symbiotic microorganisms, can be useful in developing strategies to facilitate sustainable agriculture in saline soils. Besides developing mechanisms for stress tolerance, microorganisms can also impart some degree of tolerance to plants towards abiotic stresses like drought, chilling injury, salinity , metal toxicity and high temperature. In the last decade, bacteria belonging to different genera including Rhizobium , Bacillus , Pseudomonas , Pantoea , Paenibacillus , Burkholderia , Achromobacter , Azospirillum , Microbacterium , Methylobacterium , Variovorax , Enterobacter etc.

Use of these microorganisms per se can alleviate stresses in agriculture thus opening a new and emerging application of microorganisms. Microbial elicited stress tolerance in plants may be due to a variety of mechanisms proposed from time to time based on studies done.

Production of indole acetic acid, gibberellins and some unknown determinants by PGPR, results in increased root length, root surface area and number of root tips, leading to an enhanced uptake of nutrients thereby improving plant health under stress conditions Egamberdieva and Kucharova, Plant growth promoting bacteria have been found to improve growth of tomato, pepper, canola, bean and lettuce under saline conditions Barassi et al.

Some PGPR strains produce cytokinin and antioxidants, which result in abscisic acid ABA accumulation and degradation of reactive oxygen species.

High activities of antioxidant enzymes are linked with oxidative stress tolerance Stajner et al. Many aspects of plant life are regulated by ethylene levels and the biosynthesis of ethylene is subjected to tight regulation, involving transcriptional and post-transcriptional factors regulated by environmental cues, including biotic and abiotic stresses Hardoim et al.

Under stress conditions, the plant hormone ethylene endogenously regulates plant homoeostasis and results in reduced root and shoot growth. In the presence of ACC deaminase producing bacteria, plant ACC is sequestered and degraded by bacterial cells to supply nitrogen and energy. Furthermore, by removing ACC, the bacteria reduce the deleterious effect of ethylene, ameliorating stress and promoting plant growth Glick, The complex and dynamic interactions among microorganisms, roots, soil and water in the rhizosphere induce changes in physicochemical and structural properties of the soil Haynes and Swift, Microbial polysaccharides can bind soil particles to form microaggregates and macroaggregates.

Plant roots and fungal hyphae fit in the pores between microaggregates and thus stabilize macroaggregates. Plants treated with Exo-poly saccharides EPS producing bacteria display increased resistance to water and salinity stress due to improved soil structure Sandhya et al. Chen et al. Introduction of proBA genes derived from B.

Increased production of proline along with decreased electrolyte leakage, maintenance of relative water content of leaves and selective uptake of K ions resulted in salt tolerance in Zea mays coinoculated with Rhizobium and Pseudomonas Bano and Fatima, Rhizobacteria inhabiting the sites exposed to frequent stress conditions, are likely to be more adaptive or tolerant and may serve as better plant growth promoters under stressful conditions.

Moreover Yao et al. In a study carried out by Naz et al. Noteworthy, the isolates produced ABA in a concentration much higher than that of previous reports. Likewise Upadhyay et al. Jha et al. Plants inoculated with endophytic bacterium P. While at higher salinity levels, a mixture of both P. Nia et al. The component of grain yield most affected by inoculation was grains per plant.

Plants inoculated with saline-adapted Azospirillum strains had higher N concentrations at all water salinity levels. Sadeghi et al. They observed significant increases in germination rate, percentage and uniformity, shoot length and dry weight compared to the control. Applying the bacterial inocula increased the concentration of N, P, Fe and Mn in wheat shoots grown in normal and saline soil and thus concluded that Streptomyces isolate has potential to be utilized as biofertilizers in saline soils.

More recently Ramadoss et al. In particular, Hallobacillus sp. These results indicate that halotolerant bacteria isolated from saline environments have potential to enhance plant growth under saline stress through direct or indirect mechanisms and would be most appropriate as bioinoculants under such conditions.

The isolation of indigenous microorganisms from the stress affected soils and screening on the basis of their stress tolerance and PGP traits may be useful in the rapid selection of efficient strains that could be used as bioinoculants for stressed crops. Some of the advances and researches carried out in evaluating role of rhizobacteria as salinity stress remediators have been summarized in Table 1. An ideal sustainable agricultural system is one which maintains and improves human health, benefits producers and consumers both economically and spiritually, protects the environment, and produces enough food for an increasing world population.

One of the most important constraints to agricultural production in world is abiotic stress conditions prevailing in the environment. Plant-associated microorganisms can play an important role in conferring resistance to abiotic stresses.

These organisms could include rhizoplane, rhizosphere and endophytic bacteria and symbiotic fungi and operate through a variety of mechanisms like triggering osmotic response, providing growth hormones and nutrients, acting as biocontrol agents and induction of novel genes in plants.

The development of stress tolerant crop varieties through genetic engineering and plant breeding is essential but a long drawn and expensive process, whereas microbial inoculation to alleviate stresses in plants could be a more cost effective environmental friendly option which could be available in a shorter time frame. Taking the current leads available, concerted future research is needed in this area, particularly on field evaluation and application of potential organisms as biofertilizers in stressed soil.

Peer review under responsibility of King Saud University. National Center for Biotechnology Information , U. Saudi J Biol Sci. Published online Dec 9. Author information Article notes Copyright and License information Disclaimer.

Pooja Shrivastava: moc. This article has been cited by other articles in PMC. Abstract Salinity is one of the most brutal environmental factors limiting the productivity of crop plants because most of the crop plants are sensitive to salinity caused by high concentrations of salts in the soil, and the area of land affected by it is increasing day by day.

Introduction The beginning of 21st century is marked by global scarcity of water resources, environmental pollution and increased salinization of soil and water. Problem of soil salinization Soil salinity is an enormous problem for agriculture under irrigation. Impact of salinity on plants Agricultural crops exhibit a spectrum of responses under salt stress.

Amelioration of salinity Salinization can be restricted by leaching of salt from root zone, changed farm management practices and use of salt tolerant plants. Open in a separate window. Figure 1. Different approaches for improvement of salt tolerance in agricultural crops. Use of salt tolerant crops and transgenics Using the salt-tolerant crops is one of the most important strategies to solve the problem of salinity.

Microbes: abiotic stress alleviation tool in crops Several strategies have been developed in order to decrease the toxic effects caused by high salinity on plant growth, including plant genetic engineering Wang et al.

Alleviation of abiotic stress in plants by rhizospheric bacteria Besides developing mechanisms for stress tolerance, microorganisms can also impart some degree of tolerance to plants towards abiotic stresses like drought, chilling injury, salinity , metal toxicity and high temperature.

Table 1 Role of plant growth promoting bacteria in salinity stress alleviation in plants. Plant growth promoting bacterial species Crop plant Effect References Achromobacter piechaudii Tomato Lycopersicon esculentum Reduced levels of ethylene and improved plant growth Mayak et al.

Tafalla ACC deaminase activity and enhanced uptake of essential nutrients Kohler et al. ACC deaminase activity and increased water use efficiency Ahmad et al. Conclusion An ideal sustainable agricultural system is one which maintains and improves human health, benefits producers and consumers both economically and spiritually, protects the environment, and produces enough food for an increasing world population.

Footnotes Peer review under responsibility of King Saud University. References Ahmad M.