Showing papers on "Soil salinity published in 1999"

Contributions of groundwater conditions to soil and water salinization

Abstract: Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or human-induced processes Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration, hydrolysis, and leakage between aquifers Salinity increases from catchment divides to the valley floors and in the direction of groundwater flow Salinization is explained by two main chemical models developed by the authors: weathering and deposition These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden in the catchments Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water In all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt At a small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis Saline groundwater flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges in lakes, where most of the saline groundwater is concentrated In the hummocky terrains of the Northern Great Plains Region, Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction with the formation of saline soils and seepages On a regional scale within closed basins, this process can create playas or saline lakes In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path and forms a saline zone at the distal end The saline zone in each rift forms a closed ridge, which coincides with the closed trough of the groundwater-level map The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate precipitation and dissolution of capillary salts

Salinity Tolerance Mechanisms of Grasses in the Subfamily Chloridoideae

Abstract: Forage grasses and turfgrasses are increasingly being subjected to salinity stress, due to accelerated salinization of irrigated agricultural lands worldwide, and to increased use of reclaimed and other secondary water sources for irrigating turfgrass landscapes. The objective of this study was to examine salinity responses of a number of important forage and turfgrass genera in the subfamily Chloridoideae in attempt to gain understanding of salinity tolerance mechanisms operating in this subfamily. Grasses were exposed to salinities up to 600 mM NaCl in solution culture. Salinity tolerance decreased in the following order: Distichlis spicata var. stricta (Torr.) Beetle > Sporobolus airoides (Torr.) Torr. > Cynodon dactylon (L.) Pers. = Zoysia japonica Steud. > Sporobolus cryptandrus (Torr.) A. Gray. > Buchloe dactyloides (Nutt.) Engelm. > Bouteloua curtipendula (Michx.) Torr. Relative root length (RL) and relative root weight (RW) increased under saline conditions, relative to control, in salt tolerant grasses. Leaf sap osmolality, Na + , Cl - , and proline concentrations were negatively correlated and glycinebetaine was positively correlated with salinity tolerance. Bicellular salt glands were observed on leaves of all species. Salinity tolerance was positively correlated with Na + and Cl - salt gland secretion rates. Within the subfamily Chloridoideae, salinity tolerance was associated with saline ion exclusion, facilitated by leaf salt gland ion secretion, and with accumulation of the compatible solute glycinebetaine.

Crop Response and Management of Salt-Affected Soils

Abstract: Salinity is a major factor reducing plant growth and productivity throughout the world [1]. Approximately 10% of the world’s 7 10 ha arable land surface consists of saline or sodic soils. The percentage of cultivated lands affected by salts is even greater. Of the 1.5 10 ha cultivated lands, 23% are considered saline and another 37% are sodic. Although the data are tenuous, it has been estimated that one-half of all irrigated lands (about 2.5 10 8 ha) are seriously affected by salinity or waterlogging [2]. Historically, soil salinity contributed to the decline of several ancient civilizations [3]. Despite the advanced management technologies available today, salinization of millions of hectares of land continues to reduce crop production severely in the United States and worldwide [4]. The National Academy of Sciences [5] includes salinization of soils and waters as one of the leading processes contributing to a worldwide biological catastrophe. Sustained and profitable production of crops on salt-affected soils is possible if appropriate on-farm management decisions are made. To be successful, growers require an understanding of how plants respond to salinity, the relative tolerances of different crops and their sensitivity at different stages of growth, and how different soil and environmental conditions affect salt-stressed plants. This chapter discusses the effects of soil and water salinity on agronomic and horticultural crop plants, presents data on the tolerance of crops to salinity, and considers consequences of various cultural and management practices on crop yield responses.

Salt Marsh Diking and Restoration: Biogeochemical Implications of Altered Wetland Hydrology.

Abstract: / In salt marshes, most biomass plus large reserves of biologically important N, P, Fe, and S are sequestered below ground under saline, waterlogged, and anaerobic conditions. Thus, hydrologic alterations such as diking and ditch drainage that reduce salinity and increase peat aeration can cause radical changes in the composition of salt marsh soils.Experimental short-term desalination and drainage of salt marsh cores in greenhouse microcosms caused Spartina production to increase after one growing season, reflecting decreased salt stress and sulfide toxicity. However, production thereafter declined, likely due to pyrite oxidation and acidification in drained treatments and sulfide accumulation in waterlogged treatments.A survey of longer-term (decadal) effects of diking on peat composition of Cape Cod, Massachusetts, USA, marshes revealed acidification, Fe(II) mobilization, and decreased organic content in drained sites. Despite the aerobic decomposition of organic matter, abundant nutrients remained as sorbed NH4 and mineral-bound PO4. In diked, seasonally waterlogged sites, porewater alkalinity, sulfide, ammonium and orthophosphate were much lower, and organic solids higher, than in adjacent natural marsh.Seawater was added to cores from diked marshes to study the effects of tidal restoration. Salination of the drained peat increased porewater pH, alkalinity, ammonium, orthophosphate, Fe, and Al; copious ammonium N, and Fe(II) for sulfide precipitation favored Spartina growth. Salination of diked-waterlogged peat increased sulfate reduction and caused 6-8 cm of sediment subsidence. The resulting increase in porewater sulfides and waterlogging decreased vigor of transplanted Spartina alterniflora. Results indicate that seawater restoration should proceed cautiously to avoid nutrient loading of surface waters in drained sites or sulfide toxicity in diked-waterlogged marshes.KEY WORDS: Salt marsh; Diking; Biogeochemical cycling; Restoration; Massachusettshttp://link.springer-ny.com/link/service/journals/00267/bibs/24n1p111.html

Is zonation on coastal sand dunes determined primarily by sand burial or by salt spray? A test in New Zealand dunes

Abstract: There has long been controversy on which environmental factor is the predominant determinant of community zonation on sand dunes. It is demonstrated here that, on a dune system in southern New Zealand, several environmental factors that could limit growth all vary along the sea-to-inland sand dune zonation: soil moisture, soil nutrients, wind exposure, sand burial, salt spray and soil salinity. Correlation of the responses of 30 species to experimental stress (burial, darkness, rooting-medium salinity and salt spray) with the zonation of the species in the field indicates that, in the four dune systems studied, sand burial and salt are both important, with salt generally being the more important. However, the relative importance of the factors differs between sites.

Effect of salinity on growth, water use and nutrient use in radish (Raphanus sativus L.)

Abstract: Radish (Raphanus sativus L.) plants were grown at five soil salinity levels (1, 2, 4, 9 and 13 dS m-1) to analyse the effects on growth, dry matter partitioning, leaf expansion and water and nutrient use. Salinity was varied by proportionally changing the concentration of all macro nutrients. When the electrical conductivity (EC) of the soil solution increased from 1 to 13 dS m-1, the influx concentration of the nutrients absorbed by the plants (the ratio between the uptakes of nutrients and water) increased only from 1.6 to 3.5 dS m-1. The total nutrient uptake showed an optimum at an EC of the soil solution of about 4 dS m-1. The data suggest that at low salinity level (≤ 2 dS m-1) the nutrient uptake was limited by availability while at high salinity (>4 dS m-1) it was limited by the growth of the plant. Total water use by the plants decreased and water use efficiency increased at high salinity. Plant growth was optimal at 2–4 dS m-1. At salinities higher than 4 dS m-1 total plant dry weight decreased 2.8% per dS m-1. About 80% of the growth reduction at high salinity could be attributed to reduction of leaf area expansion and hence to reduction of light interception. The remaining 20% of the salinity effect on growth was most likely explained by a decrease in stomatal conductance. The small leaf area at high salinity was related to a reduced specific leaf area and increased tuber/shoot weight ratio. The latter could be attributed to tuber formation starting at a smaller plant size at high salinity.

Mangrove species zonation and soil redox state, sulphide concentration and salinity in Gazi Bay (Kenya), a preliminary study

Abstract: The relationship between soil redox state, sulphide concentration, salinity and spatial patterns of mangrove species distribution was investigated in the mangrove forest of Gazi Bay (Kenya). Field measurements were conducted to examine the relationship between species distribution along a band transect of 280 m and soil redox potential (Eh) and sulphide patterns, as well as the indirectly related (through flooding regimes) soil salinity. Of the three major. species Avicennia marina, Ceriops tagal and Rhizophora mucronata present along the transect, only the distribution of the latter correlated with the measured soil variables, R. mucronata being absent from the less-reduced zone with high salinity. Bruguiera gymllorhiza and Heritiera littoralis occur in minor populations, they are restricted to the saline, sulphide-poor and less-reduced substrates. From the results it is concluded that soil redox potential (Eh), sulphide concentration and salinity may contribute to structure mangroves through the distribution of dominant species, however in combination with other environmental conditions and processes of vegetation dynamics.

Evaluating soil salinity status from bulk electrical conductivity and permittivity

Abstract: Summary In the range of volumetric water content, θ, from about 0.12 cm3 cm–3 to saturation the relation between bulk electrical conductivity, Cb, and bulk electrical permittivity, e, of mineral soils was observed to be linear. The partial derivative ∂Cb/∂e appeared independent of the moisture content and directly proportional to soil salinity. We found that the variable Xs = ∂Cb/∂e determined from in situ measurements of Cb(θ > 0.2) and e(θ > 0.2) can be considered as an index of soil salinity, and we call it the ‘salinity index’. Knowing the index and sand content for a given soil we could calculate the electrical conductivity of the soil water, Cw, which is a widely accepted measure of soil salinity. The two variables from which the salinity index can be calculated, i.e. Cb and e, can be read simultaneously from the same sensor by time-domain reflectometry. Quantities and symbols a constant /dS m–1 b constant c constant /dS m–1 Cb electrical conductivity of bulk soil /dS m–1 Cb′ constant equal to 0.08 dS m–1 Cs electrical conductivity of a solution used to moisten soil samples /dS m–1 Cw electrical conductivity of soil water defined as the soil salinity /dS m–1 Cwref reference salinity (that truly existing) resulting from the procedure of moistening samples, expressed as Cs + Cr/dS m–1 Cr baseline value of Cs due to residual soluble salts present in the soil /dS m–1 d constant D dry soil bulk density /g cm–3 l slope r ratio S sand content /% by weight t time /s Xs salinity index /dS m–1 Xsi initial salinity index when distilled water is used to moisten soil samples /dS m–1 Y a moisture-independent salinity-dependent variable /dS m–1 z coordinate along direction of flow of the soil solution e′ constant equal to 6.2 e relative bulk electrical permittivity (dielectric constant) of the soil θ volumetric water content determined thermogravimetrically using oven-drying /cm3 cm–3

Soil disturbance, flood management, and riparian woody plant establishment in the Rio Grande floodplain

Abstract: The exotic saltcedar (Tamarix ramosissima) has become the dominant woody plant in many riparian systems in the southwestern United States. We evaluated the effects of saltcedar clearing and overbank river flooding on recruitment of cottonwood (Populus fremontii) and saltcedar vegetation in the Rio Grande floodplain of central New Mexico, USA in 1993 and 1994. Overbank flooding coincided with the natural river hydrograph. After two seasons of growth, cleared areas supported more 1993 cohort cotton-woods and saltcedar than uncleared controlled areas. There were no differences between cleared and uncleared areas for the 1994 cohort after one growing season. Although there was a 2-week difference in the date of peak river flows between 1993 and 1994, similar seedling densities of both species were recorded for both years. The descending limb of the 1993 hydrograph was more gradual than the 1994 hydrograph, however, resulting in a higher survival rate of 1993 seedlings. Soil texture, soil salinity, elevation, and soil moisture data were collected from all plots and compared with seedling densities for each seedling sample date. Elevation and soil moisture indices were the most influential variables on seedling density. Decreasing soil moisture variables resulted in consistent seedling mortality for all species in cleared and uncleared plots for both cohorts. Secondary channels developed as a result of vegetative clearing where natural river fluvial processes provided topographic relief and sediment deposition for seedling establishment. Greater densities of cottonwoods and coyote willows (Salix exigua) were found on these deposits compared with remaining portions of cleared plots. Saltcedar clearing in conjunction with peak river flows in late May or early June encourages recruitment of native riparian plants, particularly along sand deposits created as a result of secondary channel development. Receding flows correlated with a receding water-table level of about 2 cm/day enhances native seedling densities relative to saltcedar.

Salinity Duration and Concentration Affect Fruit Yield and Quality, and Growth and Mineral Composition of Melon Plants Grown in Perlite

Abstract: The shortage of good quality water in semiarid zones necessitates the use of saline water for irrigation. In order to simulate the usage of brackish irrigation water in greenhouse melon (Cucumis melo L. cv. Galia) culture in perlite, plants were supplied with nutrient solutions containing 0 (control), 20, 40, and 60 mM NaCI applied at four different times. Treatments were applied during early vegetative growth [14 days after transplanting (DAT)], beginning of flowering (37 DAT), beginning of fruit set (56 DAT), and beginning of fruit ripening (71 DAT). All vegetative and fruit yield parameters were significantly reduced when salinization was started 14 DAT. This inhibitory effect of salinity was progressively lessened when salinity was imposed at later dates. This suggests that the response of melons to salinity depends on the duration of exposure to saline water. Salinity treatments increased fruit reducing sugars, acidity, and total soluble solids. Fruit yield reduction at each salinization time was correlated with salinity levels, but there was some evidence of a nutrient imbalance, since leaf concentrations of N-NO 3 , and especially K, were low at higher salinities. These results indicate that brackish waters can be used for growing melon with minimum yield losses if concentration and duration of exposure are carefully monitored.

Effects of salinity on chlorophyll fluorescence and photosynthesis of barley (Hordeum vulgare L.) grown under a triple-line-source sprinkler system in the field

Abstract: In flag leaves of four cultivars of barley (Hordeum vulgare L.) grown in the field under a triple-line-source sprinkler system, that produces a linear soil salinity gradient, a decrease in net carbon dioxide assimilation rate (PN) and stomatal conductance for water vapour (gs) was found. These changes were related to salinity tolerance at moderate salinity. With increasing salinity, PN was saturated at low irradiances and stomatal frequencies increased. A decrease in photosystem 2 (PS2) efficiency was not found in the field after dark adaptation even at high salinity. Salinity induced only small decreases in the actual PS2 efficiency at midday steady-state photosynthesis, indicating that the photosynthetic electron transport was little affected by salinity. Therefore, using PS2 efficiency estimates in attached leaves is probably not a useful tool to screen barley genotypes grown under saline conditions in the field for salinity tolerance. In contrast, excised flag leaves from high salinity plots, once in the laboratory, exhibited a decrease in the variable to maximum chlorophyll fluorescence ratio as compared to excised leaves from control plants. On the other hand, the PN rate might allow for a good discrimination between tolerant and non-tolerant cultivars.

Interactions between Rising CO2, Soil Salinity, and Plant Growth

Abstract: Publisher Summary This chapter describes the global impact of salinity and the consequences of elevated CO 2 on plant growth and soil salinity. The cellular and whole plant mechanisms by which salinity affects growth are described, with emphasis on the mechanism by which elevated CO 2 might interact with salinity. Much of the saline land in the world has been caused by human activities: by clearing, overgrazing, or the installation of irrigation schemes. The result of these activities is termed “secondary salinization.” The long-term productivity of the global agricultural system as a whole is declining, as is ecosystem stability. Rising CO 2 levels could increase the productivity of cultivated species and natural vegetation on saline soils, but it may also increase soil salinity. Elevated CO 2 can increase the growth rate of crops, pastures, and trees, but because it also increases their water use efficiency, it may alter the soil-plant water balance in a way that has adverse consequences for land with saline groundwater, where any factor that causes the water table to rise will increase the rate of salinization of the topsoil.

Germination and growth responses of hybridizing Carpobrotus species (Aizoaceae) from coastal California to soil salinity.

Abstract: Germination, growth, and physiological responses of hybridizing Carpobrotus from coastal California to soil salinity were studied. Hybrids are presumably the result of hybridization and introgression between the exotic Carpobrotus edulis, a succulent perennial invading coastal habitats, and the native or long-naturalized C. chilensis. Germination responses were investigated at 0, 10, 20, and 50% seawater. Seedling growth and physiology were compared by irrigating seedlings with solutions of the same seawater concentrations and in low and high nutrients. Germination was inhibited in the presence of salt, but recovered after transferring the seeds to fresh water. Seeds exposed to salt had higher final germination rates than control. Growth of Carpobrotus was slightly enhanced by low seawater concentrations but reduced at high salinity at both nutrient regimes. Leaf cell sap osmolarity increased with increasing soil salinity, and taxa did not differ significantly in this physiological adjustment. Leaf carbon isotope ratios (∂(13)C) ranged from -28 to -22‰ and became less negative at higher salinities, indicating an improved water use efficiency in the seedlings at high salt concentrations. In addition, ∂(13)C values were generally less negative at high than at low nutrients. Differences among taxa were generally small. The results show that salinity affects both establishment and growth of hybridizing Carpobrotus. The overall weak species differences in salt tolerance indicate that the exotic C. edulis can occupy the same sites as C. chilensis in terms of salinity. The similarity of hybrids in their response to salinity suggests that they may contribute to the invasion by Carpobrotus.

Emergence and seedling growth of soybean cultivars and maturity groups under salinity

Abstract: Soybean is an important agricultural crop and has, among its genotypes, a relatively wide variation in salt tolerance As measured by vegetative growth and yield, however, the achievement or failure of a high emergence ratio and seedling establishment in saline soils can have significant economic implications in areas where soil salinity is a potential problem for soybean This study was conducted to determine the effects of salinity, variety and maturation rate on soybean emergence and seedling growth Included in the study were the variety ‘Manokin’; four near-isogenic sibling lines of the variety ‘Lee’ belonging to maturity groups IV, V, VI and VII; and the variety ‘Essex’ and two of its near-isogenic related lines representing maturity groups V, VI and VII, respectively Field plots were salinized with sodium chloride and calcium chloride salts prior to planting The soybeans were irrigated with furrow irrigation which redistributed the salts towards the tail ends of the field plots Elevated soil salinity near the tail ends of the field significantly reduced soybean emergence rate, shoot height and root length No significant reduction was found for emergence or seedling growth of variety ‘Manokin’ when the electrical conductivity of soil solution extract (ECe) was less than 3 dS m−1 Soybean emergence and seedling growth was significantly reduced when soil ECe reached about 11 dS m−1 Maturity groups V and VII of variety ‘Lee’ or V and VI of ‘Essex’ appeared to be more sensitive to salinity stress than other maturity groups Salt tolerance of different genotypes and maturity groups should be considered, among other limiting factors, in minimizing salinity effects on soybean growth

Effects of kinetin on growth, grain yield and some mineral elements in wheat plants growing under excess salinity and oxygen deficiency

Abstract: Wheat plants, 22d. old, were exposed to wide range of soil water osmotic potential (Ψs = 0 to −1.2 MPa) induced by NaCl and CaCl2 treatments in combination with roots maintained under aerobic (drained at field capacity) or nonaerobic (flooded) conditions in the soil, and sprayed with 10 mg L−1 kinetin solution. In drained plants, not receiving kinetin, increased soil salinity resulted in appreciable inhibition of shoot growth and reduction in chlorophyll (Ch1.), soluble sugars (SS) contents and grain yield. Shoot growth, Ch1. content, soluble sugars and grain yield were significantly lower for flooded plants than unflooded analogues over the entire Ψs range. Both salinity and waterlogging synergize to increase Na+, Ca+ and Cl− accumulation in shoot tissues and to decrease the stability of leaf membranes to either dehydration (40% polyethylene glycol 6000) or heat (51 °C) stress. The ratio of K+/Na+ transported to shoots under aerobic and anaerobic conditions decreased progressively on salinization. The association between the internal mineral element concentrations was largely affected by kinetin treatment. Kinetin application ameliorated the deleterious effects of salinity and oxygen deficiency. It reduced Na+, Ca2+ and Cl− accumulation and improved K+ uptake under salinity and waterlogging stresses. Increased K+/Na+ ratio helped the plants to avoid Na+ toxicity and enhanced shoot growth and grain yield. Kinetin also reduced membrane injury by dehydration and heat stresses and improved the water status of plants under both aerobic and anaerobic conditions. The effects of single factors (Soil salinity ‘Ψs’, soil waterlogging ‘WL’ and Kinetin ‘Kin’) and their interactions (Ψs × WL, Ψs × Kin, WL × Kin and Ψs × WL × Kin) were shown by analysis of variance to be statistically significant for most parameters tested. Calculation of the coefficient of determination (η+) led to three important findings. (1) Salinity (Ψs) was dominant in affecting leaf relative water content (RWC), shoot dry mass, grain yield, stability of leaf membranes to dehydration stress and the contents of Na+, Ca2+, Mg2+ and Cl−. (2) Kinetin (Kin) had a dominant effect on the stability of leaf membranes to heat stress as well as on chlorophyll and soluble sugars contents. (3) The share of waterlogging (WL) was dominant for K+ content. It can be concluded that kinetin application helped wheat plants to grow successfully in the areas subjected to combined effects of salinity and oxygen deficiency, such as in salt marshes.

Genesis, properties and sensitivity of Antarctic Gelisols

Abstract: According to the newest version of the US Soil Taxonomy permafrost-affected soils are Gelisols. Antarctic Gelisols in the cold deserts of the Ross Sea sector are formed under extreme conditions of low temperature and aridity. The main soil forming processes are oxidation and salinization, with almost complete absence of organic matter. The oldest soils date from around 13 Ma. The origin of most soil salts is atmospheric, linking these soils to those in other parts of the world through atmospheric processes. The soils have water contents in the active layer of the most arid areas <1%. With decreasing latitude or proximity to the coast in East Antarctica and the Antarctic Peninsula, soil water contents increase and the soils support a range of soil organisms and plant species. At latitudes ≤66°S organic matter accumulation and several other pedogenic processes such as cryoturbation, mineral weathering, brunification, acidification, podzolization and redoximorphism occur. In addition, these soils receive nitrogen and phosphorus from seabirds. In most places summer thaw lasts little more than six weeks; thaw depths range from around 10–100 cm. A critical factor in the soil development is the albedo of the soil surface, since the absorbed energy controls weathering processes. The extreme fragility of the soils in the arid Ross Sea sector is largely due to the absence of structure, cohesion, moisture and organic materials. Recovery from physical human disturbances is in the order of hundreds to thousands of years. In East Antarctica and the Antarctic Peninsula plant and organisms growth is similarly slow and ecosystems are susceptible to human impact. The occurrence of many old soils at high inland elevation indicates that little response to global climatic change would be expected there. For the much younger soils in East Antarctica and the Antarctic Peninsula, when mean annual summer temperatures are higher, responses to global change and change in sea level may be significant.