Response of mesquite to nitrate and salinity in a simulated phreatic environment: Water use,dry matter and mineral nutrient accumulation

Mesquite plants (Prosopis glandulosa var. Torreyana) were grown in 2-m long columns 20 cm in diameter, and provided with a constant, stable ground water source 10 cm above the sealed base of the column. Ground water contained 0, 1 or 5 mM nitrate, or a mixed salt solution (1.4, 2.8, or 5.6 dS m^-1) with the ionic ratios of ground water found in a field stand of Prosopis at Harper's Well (2.8 dS m^-1). Water uptake in the highly salinized columns began to decrease relative to low salt columns when soil salinity probes 30 cm above the column base read approximately 28 dS m^-1, a potential threshold for mesquite salt tolerance. Prosopis growth increased with increasing nitrate, and decreased with increasing salinity. Water use efficiency was little affected by treatment, averaging approximately 2 g dry matter L^-1 water used. Most fine roots were recovered from a zone about 25 cm above the ground water surface where water content and aeration appeared to be optimal for root growth. Root-shoot ratio was little affected by nitrate, but increased slightly with increasing salinity. Plant tissue P concentrations tended to increase with increasing salinity and decrease with increasing N, approaching potentially deficient foliage concentrations at 5 mM nitrate. The whole-plant leaf samples increased in sodium concentration both with added salt and with added nitrate. Foliar manganese concentrations increased with increasing salt in the absence of nitrate. Concentrations of sodium in leaves were low (<10 g kg^-1), considering the high salt concentrations in the ground water. Prosopis appears to exclude sodium very effectively, especially from its younger leaves. Although Prosopis is highly salt tolerant, the degree to which it utilizes soil nitrate in place of biologically fixed N may lower its salinity tolerance and affect its nutrient relations in phreatic environments.     

Improved Tolerance of <Emphasis Type="Italic">Acacia nilotica</Emphasis> to Salt Stress by Arbuscular Mycorrhiza, <Emphasis Type="Italic">Glomus fasciculatum</Emphasis> may be Partly Related to Elevated K/Na Ratios in Root and Shoot Tissues

A pot experiment was conducted to examine the effect of arbuscular mycorrhizal fungus, Glomus fasciculatum, and salinity on the growth of Acacia nilotica. Plants were grown in soil under different salinity levels (1.2, 4.0, 6.5, and 9.5 dS m⁻¹). In saline soil, mycorrhizal colonization was higher at 1.2, 4.0, and 6.5 dS m⁻¹ salinity levels in AM-inoculated plants, which decreased as salinity levels further increased (9.5 dS m⁻¹). Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to nonmycorrhizal plants. AM-inoculated plants had higher P, Zn, and Cu concentrations than uninoculated plants. In mycorrhizal plants, nutrient concentrations decreased with the increasing levels of salinity, but were higher than those of the nonmycorrhizal plants. Mycorrhizal plants had greater Na concentration at low salinity levels (1.2, 4.0 dS m⁻¹), which lowered as salinity levels increased (6.5, 9.5 dS m⁻¹), whereas Na concentration increased in control plants. Mycorrhizal plants accumulated a higher concentration of K at all salinity levels. Unlike Na, the uptake of K increased in shoot tissues of mycorrhizal plants with the increasing levels of salinity. Our results indicate that mycorrhizal fungus alleviates deleterious effects of saline soils on plant growth that could be primarily related to improved P nutrition. The improved K/Na ratios in root and shoot tissues of mycorrhizal plants may help in protecting disruption of K-mediated enzymatic processes under salt stress conditions.     

The response of potatoes (Solunum tuberosum L.) to salinity: plant growth and tuber yields in the arid desert of Israel

The response of potato cultivars to water salinity was studied under field conditions in sandy loessial soil in the arid desert of Southern Israel. The potatoes were drip-irrigated with water of three different salinities: water commonly used for irrigation (1.0–1.4 dS m^-1); saline water from a local well (6.1–6.9 dS m^-1); and a mixture of the two (3.84.3 dS m^-1). Salinity retarded plant emergence, enhanced haulm senescence and reduced growth of both haulms and tubers. Increasing the salinity progressively reduced tuber yields. Application of the saline water well after plant establishment (Expt A) decreased tuber yields by 615% and 22–31% in the intermediate and the high salinities, respectively. When irrigation with saline water was started soon after planting (Expt B), tuber yields were decreased by 0–17% and 21–79% in the intermediate and the high salinities, respectively. When the tubers emerged in salinised soil, tuber yields were decreased by 21–54% and 42–59% in the intermediate and the high salinities, respectively. A differential response of various cultivars to salinity was observed. None of the potato cultivars or clones exhibited exceptional tolerance to severe salinity. The earlier maturing cvs Atica and Désirée were the least susceptible to the moderate salinity imposed throughout the entire growing season; however, no association was noted between maturation time and the response to salinity.     

Alleviation of salinity stress in chickpea byRhizobium inoculation or nitrate supply

Influence of inoculation with efficient rhizobia or nitrate fertilization in alleviating salinity (NaCl, CaCl₂ and Na₂SO₄) stress was investigated in sand culture experiments. Shoot dry mass declined beyond salinity level corresponding to electrical conductivity (EC) 5.6 dS m^?1 in control or in inoculated plants and after EC 7.4 dS m^?1 in nitrate fed ones. Root growth was more sensitive and decreased at EC 3.3 dS m^?1. Nitrate reductase activity in leaves reduced at EC 3.3 dS m^?1 but in inoculated and nitrate fed plants it reduced at EC 5.6 dS m^?1. Na⁺ accumulation increased at EC 5.6 and 7.4 dS m^?1 in roots and, shoots, respectively. In inoculated and nitrate fed plants Na⁺ content in roots increased at EC 7.4 dS m^?1. Content of Ca²⁺ increased slightly only in shoots and content of K⁺ was unaffected. Besides inoculation, application of small doses of nitrogen should prove beneficial for legume cultivation in saline soils.     

Effect of salinity and inoculation on growth,nitrogen fixation and nutrient uptake ofVigna radiata (L.) Wilczek

This study reports the effect of salinity and inoculation on growth, ion uptake and nitrogen fixation byVigna radiata. A soil EC_e level of 7.5 dS m⁻¹ was quite detrimental causing about 60% decline in dry matter and grain yield of mungbean plants whereas a soil EC_e level of 10.0 dS m⁻¹ was almost toxic. In contrast most of the studied strains of Rhizobium were salt tolerant. Nevertheless, nodulation, nitrogen fixation and total nitrogen concentration in the plant was drastically affected at high salt concentration. A noticeable decline in acetylene reduction activity occurred when salinity level increased to 7.5 dS m⁻¹.     

Effects of salinity and nitrogen on cotton growth in arid environment

The influences of different N fertilization rates and soil salinity levels on the growth and nitrogen uptake of cotton was evaluated with a pot experiment under greenhouse conditions. Results showed that cotton growth measured as plant height was significantly affected by the soil salinity and N-salinity interaction, but not by N alone. Cotton was more sensitive to salinity during the emergence and early growth stages than the later developmental stages. At low to moderate soil salinity, the growth inhibition could be alleviated by fertilizer application. Soil salinity was a dominated factor affecting cotton’s above-ground dry mass and root development. Dry mass of seed was reduced by 22%, 52%, and 84% respectively, when the soil salinity level increased from control level of 2.4 dS m^?1 to 7.7 dS m^?1, 12.5 dS m^?1 and to 17.1 dS m^?1, respectively. N uptake increased with N fertilization at adequate rates at both low and medium soil salinities but was not influenced by over N fertilization. At higher salinities, N uptake was independent of N rates and mainly influenced by soil salinity. The uptake of K decreased with soil salinity. The concentration of Na, Cl and Ca in plant tissues increased with soil salinity with highest concentrations in the cotton leaf.     

Seasonal water use characteristics of tall wheatgrass [Agropyron elongatum (Host) Beauv.] in a saline environment

It is essential to characterize the water use of plants that have potential for the stabilization of rising saline ground-water which could lead to increases in soil salinity. In this study, several techniques were used to determine the seasonal water use characteristics of the perennial grass Agropyron elongatum (tall wheatgrass) growing in a moderately saline, dryland environment with a fluctuating shallow groundwater table varying in electrical conductivity between 0 and 10 dS m^?1. Soil conditions were examined in terms of water potential measurements, plant water sources were identified using a stable isotope of water (deuterium, ²H) and evapotranspiration was estimated using hydrological and ventilated chamber methods. Seasonal changes in soil water potential were caused by salt accumulation and soil moisture leading to changes in plant water availability, particularly in the surface soil region over summer and autumn. Evapotranspiration in A. elongatum was high over summer during the peak period of growth (4 mm d^?1), with evidence of water use from groundwater and from specific regions of the soil profile. Evapotranspiration was low during the period that A. elongatum was partially senescent in autumn (< 0.5 mm d^?1) and the lowest leaf water potential of -3 MPa that was measured occurred during this period of moderate water stress. Intermediate levels of water use (1.5 mm d^?1) were measured during winter when the entire soil profile was available for water uptake. Based on physiological characteristics, including aspects of summer water use, root morphology and salt tolerance in A. elongatum, we conclude that this species is suitable for stabilizing the level of moderately saline groundwater in parts of southern Australia, which could reduce the potential for soil salinization.     

Grafting influence on the weight and quality of tomato fruit under salt stress

Two commercial tomato cultivars were used to determine whether grafting could prevent decrease of fruit weight and quality under salt stress conditions. The cultivars Buran F1 and Berberana F1 were grafted onto rootstock ‘Maxifort’ and grown under three levels of elevated soil salinity (EC 3.80 dS m^?1, 6.95 dS m^?1 and 9.12 dS m^?1). Fruit weight reduction of grafted plants was lower (about 20–30%) in comparison with non‐grafted ones. Salt stress at the second salinity level (EC 6.95 dS m^?1) induced the highest alteration of examined growth and quality parameters. The total increase of phenols, flavonoids, ascorbate and lycopene content in the fruits of both grafted and non‐grafted plants for both cultivars had a similar trend and intensity, though some inter‐cultivar variation was observed. The possibility of grafting tomato plants to improve salt tolerance without fruit quality loss is discussed.     

Growth Stage Modulates Salinity Tolerance of New Zealand Spinach (Tetragonia tetragonioides, Pall.) and Red Orach (Atriplex hortensis L.)

The response of two speciality vegetable crops, New Zealandspinach (Tetragonia tetragonioides Pall.) and red orach (Atriplexhortensis L.), to salt application at three growth stages wasinvestigated. Plants were grown with a base nutrient solutionin outdoor sand cultures and salinized at 13 (early), 26 (mid),and 42 (late) d after planting (DAP). For the treatment saltconcentrations, we used a salinity composition that would occurin a typical soil in the San Joaquin Valley of California usingdrainage waters for irrigation. Salinity treatments measuringelectrical conductivities (EC_i) of 3, 7, 11, 15, 19 and 23 dSm^-1were achieved by adding MgSO₄, Na₂SO₄, NaCl and CaCl₂to thebase nutrient solution. These salts were added to the base nutrientsolution incrementally over a 5-d period to avoid osmotic shockto the seedlings. The base nutrient solution without added saltsserved as the non-saline control (3 dS m^-1). Solution pH wasuncontrolled and ranged from 7.7 to 8.0. Both species were saltsensitive at the early seedling stage and became more salt tolerantas time to salinization increased. For New Zealand spinach,the salinity levels that gave maximal yields (C_max) were 0,0 and 3.1 dS m^-1and those resulting in a 50% reduction of biomassproduction (C₅₀) were 9.1, 11.1 and 17.4 dS m^-1for early, midand late salinization dates, respectively. Maximal yield ofred orach increased from 4.2 to 10.9 to 13.7 dS m^-1as the timeof salinization increased from 13, to 26, to 42 DAP, respectively.The C₅₀value for red orach was unaffected by time of salt imposition(25 dS m^-1). Both species exhibited high Na⁺accumulation evenat low salinity levels. Examination of K-Na selectivity dataindicated that K⁺selectivity increased in both species withincreasing salinity. However, increased K-Na selectivity didnot explain the increased salt tolerance observed by later salinization.Higher Na-Ca selectivity was determined at 3 dS m^-1in New Zealandspinach plants treated with early- and mid-salinization plantsrelative to those exposed to late salinization. This correspondedwith lower C_maxand C₅₀values for those plants. Lower Ca uptakeselectivity or lower Ca levels may have inhibited growth inyoung seedlings. This conclusion is supported by similar resultswith red orach. High Na-Ca selectivity found only in the early-salinizationplants of red orach corresponded to the lower C_maxvalues measuredfor those plants. Copyright 2000 Annals of Botany Company New Zealand spinach, Tetragonia tetragonioides Pall., red orach, Atriplex hortensis L., salinity, stage of growth, ion accumulation, selectivity, plant nutrition     

Foliar and root absorption of Na+ and Cl− in maize and barley: Implications for salt tolerance screening and the use of saline sprinkler irrigation

Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m^–1 (30 mM NaCl and 2.8 mM CaCl₂) and for barley in 1994, 9.6 dS m^–1 (47 mM NaCl and 23.5 mM CaCl₂). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S).Saline sprinkling increased leaf sap Na⁺ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl^– concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na⁺ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na⁺ over Cl^– whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na⁺ and Cl^– than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na⁺ and Cl^– transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers     

Intrinsic water use efficiency controls the adaptation to high salinity in a semi-arid adapted plant,henna (Lawsonia inermis L.)

Adaptation to salinity of a semi-arid inhabitant plant, henna, is studied. The salt tolerance mechanisms are evaluated in the belief that gas exchange (water vapor and CO₂) should play a key role on its adaptation to salt stress because of the strong evaporation conditions and soil water deficit in its natural area of distribution. We grow henna plants hydroponically under controlled climate conditions and expose them to control (0 mM NaCl), and two levels of salinity; medium (75 mM NaCl) and high (150 mM NaCl). Relative growth rate (RGR), biomass production, whole plant and leaf structure and ultrastructure adaptation, gas exchange, chlorophyll fluorescence, nutrients location in leaf tissue and its balance in the plant are studied. RGR and total biomass decreased as NaCl concentration increased in the nutrient solution. At 75 mM NaCl root biomass was not affected by salinity and RGR reached similar values to control plants at the end of the experiment. At this salinity level henna plant responded to salinity decreasing shoot to root ratio, increasing leaf specific mass (LSM) and intrinsic water use efficiency (iWUE), and accumulating high concentrations of Na⁺ and Cl⁻ in leaves and root. At 150 mM NaCl growth was severely reduced but plants reached the reproductive phase. At this salinity level, no further decrease in shoot to root ratio or increase in LSM was observed, but plants increased iWUE, maintaining water status and leaf and root Na⁺ and Cl⁻ concentrations were lower than expected. Moreover, plants at 150 mM NaCl reallocated carbon to the root at the expense of the shoot. The effective PSII quantum yield [Y(II)] and the quantum yield of non-regulated energy dissipation [Y(NO)] were recovered over time of exposure to salinity. Overall, iWUE seems to be determinant in the adaptation of henna plant to high salinity level, when morphological adaptation fails.     

Nostoc, Microcoleus and Leptolyngbya inoculums are detrimental to the growth of wheat (Triticum aestivum L.) under salt stress

Background and aims

This study investigated the effect of cyanobacterial inoculants on salt tolerance in wheat.

Methods

Unicyanobacterial crusts of Nostoc, Leptolyngbya and Microcoleus were established in sand pots. Salt stress was targeted at 6 and 13 dS m^?1, corresponding to the wheat salt tolerance and 50 % yield reduction thresholds, respectively. Germinated wheat seeds were planted and grown for 14 (0 and 6 dS m^?1) and 21 (13 dS m^?1) days by which time seedlings had five emergent leaves. The effects of cyanobacterial inoculation and salinity on wheat growth were quantified using chlorophyll fluorescence, inductively coupled plasma-optical emission spectrometry and biomass measurements.

Results

Chlorophyll fluorescence was negatively affected by soil salinity and no change was observed in inoculated wheat. Effective photochemical efficiency correlated with a large range of plant nutrient concentrations primarily in plant roots. Inoculation negatively affected wheat biomass and nutrient concentrations at all salinities, though the effects were fewer as salinity increased.

Conclusions

The most likely explanation of these results is the sorption of nutrients to cyanobacterial extracellular polymeric substances, making them unavailable for plant uptake. These results suggest that cyanobacterial inoculation may not be appropriate for establishing wheat in saline soils but that cyanobacteria could be very useful for stabilising soils.     

Salt Tolerance ofEchinochloa crusgalli

Salt tolerance ofEchinochloa crusgalli was studied using gravel culture with root medium electrical conductivity between 3 to 25 dS m^-1. Salinity depressed germination and shoot yield. A 50 % reduction in shoot yield occurred at 15.9 dS m^-1. The plant was able to maintain its tissue water content and K concentration in the tissue water while Na, Ca and Cl increased and Mg decreased with increasing root zone salinity.     

Interactive effects of salinity and nitrogen on growth and yield of tomato plants

Summary Tomato (Lycopersicon esculentum var. VF 145) plants were grown with Typic Xerofluvents soil in a greenhouse irrigated with recycled nutrient solutions having increasing levels of N and salinity. Positive response of plants to increasing levels of N was obtained at the lowest initial salinity level of 1 dS/m (dS/m=mmho/cm, referenced at 25°C). At the higher initial salinity levels of 5 and 9 dS/m, increasing N was ineffective in counteracting adverse effects on growth and yield caused by the presence of enhanced salt concentrations of the nutrient solution. Total N uptake was linearly correlated with the total water uptake and was severely suppressed by impaired growth associated with the two higher initial salinity levels, irrespective of N levels. The effect of salinity on leaf N concentrations changed over time. Leaf Cl and P concentrations indicated a possible suppressing effect of Cl on P uptake into plant tops.Based on portions of the thesis submitted by the senior author in partial satisfaction of the requirements for the Ph.D. degree in Soil Science. Supported in part by a grant from the Kearney Foundation of Soil Science.     

Purslane (Portulaca oleracea L.): A halophytic crop for drainage water reuse systems

Drainage water reuse systems have been proposed for the west side of the San Joaquin Valley of California in order to reduce the volumes of water requiring disposal. Implementation of this system requires development of a cropping system with successively higher salt tolerance. A major limitation is the need to identify alternate species that will be suitable as the final, most salt tolerant crop in the series. These crops must be productive when irrigated with waters that are typically high in sulfate salinity and may be contaminated with potentially toxic trace elements. This study was initiated to evaluate the interactive effects of sulfate salinity and selenium on biomass production and mineral content of purslane (Portulaca oleracea). Plants were grown in greenhouse sand cultures and irrigated four times daily. Treatments consisted of three salinity levels with electrical conductivities (EC_i) of 2.1, 15.2, and 28.5 dS m^–1, and two selenium levels, 0 and 2.3 mg L^–1. In the initial harvests, shoot dry matter was reduced by 15 to 30% at 15.2 dS m^–1 and by 80 to 90% at 28.5 dS m^–1. Regrowth after clipping above the first node was vigorous and biomass from plants irrigated with 15.2 dS m^–1 water was nearly double that from the 2 dS m^–1 treatment. Purslane appears to be an excellent candidate for inclusion in saline drainage water reuse systems. It is (i) highly tolerant of both chloride- and sulfate-dominated salinities, (ii) a moderate selenium accumulator in the sulfate-system, and (iii) a valuable, nutritive vegetable crop for human consumption and for livestock forage.     

Seed priming improves the emergence potential,growth and antioxidant system of Moringa oleifera under saline conditions

Moringa oleifera is a multipurpose plant which is now being promoted as a fodder crop. The present study was conducted to induce the tolerance in moringa plants to emerge and grow under saline conditions. For this, moringa seeds were primed with aerated water (hydropriming) and moringa leaf extract (MLE) for 12 and 24 h and studied for its emergence, potential growth behaviour, mineral composition, chlorophyll contents and antioxidant activities in comparison with unprimed seeds to investigate the physiological changes in moringa plants under saline conditions. The seeds were sown in plastic pots filled with acid washed sand at four salinity levels (3, 6, 10, 14 dS m^?1) in a completely randomized design with three replications. It was found that salinity >6 dS m^?1 reduced the emergence, growth and vigour of moringa plants but hydropriming (12 h) enhanced moringa emergence at 10 dS m^?1 followed by MLE priming (12 h). Maximum aboveground biomass and photosynthetic pigments were recorded when the seeds were hydroprimed (12 h) but maximum root length and number of roots were found in MLE primed (12 h) moringa plants. Significant decrease in K⁺:Na⁺ ratio with increasing salinity levels resulted in low K⁺ and Mg²⁺ uptake and Na⁺ toxicity in moringa leaves which resulted in reduced chlorophyll contents at 14 dS m^?1 but a significant increase in chlorophyll a and b contents and total phenolics were found in hydroprimed seeds (12 h) while the antioxidant activities of superoxide dismutase, peroxidase and catalas were improved by MLE priming (12 h). This study concludes that moringa emergence and growth performance can be improved by hydropriming under saline conditions.     

The Effects of Saline Water Drip Irrigation on Tomato Yield,Quality, and Blossom-End Rot Incidence --- A 3a Case Study in the South of China

Saline water resources are abundant in the coastal areas of south China. Most of these resources still have not been effectively utilized. A 3-year study on the effects of saline water irrigation on tomato yield, quality and blossom-end rot (BER) was conducted at different lower limits of soil matric potential (-10 kPa, -20 kPa, -30 kPa, -40 kPa and -50 kPa). Saline water differing in electrical conductivity (EC) (3 dS/m, 4 dS/m, 4.5 dS/m, 5 dS/m and 5.5 dS/m) was supplied to the plant after the seedling establishment. In all three years, irrigation water with 5.5 dS/m salinity reduced the maximum leaf area index (LAI_m) and chlorophyll content the most significantly when compared with other salinity treatments. However, compared with the control treatment (CK), a slight increase in LAI_m and chlorophyll content was observed with 3~4 dS/m salinity. Saline water improved tomato quality, including fruit density, soluble solid, total acid, vitamin C and the sugar-acid ratio. There was a positive relationship between the overall tomato quality and salinity of irrigation water, as analyzed by principal component analysis (PCA). The tomato yield decreased with increased salinity. The 5.5 dS/m treatment reduced the tomato yield (Y_t) by 22.4~31.1%, 12.6~28.0% and 11.7~27.3%, respectively in 2012, 2013 and 2014, compared with CK. Moreover, a significant (P≤0.01) coupling effect of salinity and soil matric potential on Y_t was detected. Saline water caused Y_t to increase more markedly when the lower limit of soil matric potential was controlled at a relatively lower level. The critical salinity level that produced significant increases in the BER_i was 3 dS/m~4 dS/m. Following the increase in BER_i under saline water irrigation, marketable tomato yield (Y_m) decreased by 8.9%~33.8% in 2012, 5.1%~30.4% in 2013 and 10.1%~32.3% in 2014 compared with CK. In terms of maintaining the Y_t and Y_m, the salinity of irrigation water should be controlled under 4 dS/m, and the lower limit of soil matric potential should be greater than -20 kPa.     

Phytoextraction and Accumulation of Boron and Selenium by Poplar (Populus) Hybrid Clones

There has been much interest recently in central California for reusing drainage water to grow trees. A sand-culture study was conducted to investigate the accumulation of boron (B) and selenium (Se) in eight hybrid poplar (Populus) clones irrigated with synthetic agricultural effluent containing increasing levels of chloride salt, B, and Se. Electrical conductivity (EC) ranged from 1.5 to 15 dS m^-1, B levels from 1 to 5 mg L^-1, and Se levels from 100 to 500 μg L^-1. Compared with all tree organs, the leaves accumulated the greatest concentrations of B and Se at the time of harvest. The results show that pooled leaf B concentrations were positively correlated with EC levels (r = 0.78, P < 0.001) and negatively correlated (r = -0.53, P < 0.001) with leaf dry matter for all clones at all tested B levels. Combined leaf and stem Se data show, respectively, a significant decrease (P < 0.05 level) in tissue accumulation of Se with increased salinity. Toxicity symptoms (e.g., burning leaf margins, shoot die back) occurred in most clones grown at 12 and 15 dS m^-1 treatments leading to leaf abscission. Based on the data, clone 49177 (Populus trichocarpa × P. deltoidus) best tolerated the tested parameters among the clones and accumulated the greatest amount of B and Se. The moderate ability of the Populus species to remove and accumulate B and Se from saline effluent is most effective at salinity levels less than 7 dS m^-1.     

Effect of salinity on mycorrhizal onion and tomato in soil with and without additional phosphate

Summary Vesicular-arbuscular mycorrhizal fungi (VAM) are known to increase plant growth in saline soils. Previous studies, however, have not distinguished whether this growth response is due to enhanced P uptake or a direct mechanism of increased plant salt tolerance by VAM. In a glasshouse experiment onions (Allium cepa L.) were grown in sterilized, low-P sandy loam soil amended with 0, 0.8, 1.6 mmol P kg^–1 soil with and without mycorrhizal inoculum. Pots were irrigated with saline waters having conductivities of 1.0, 2.8, 4.3, and 5.9 dS m^–1. Onion colonized withGlomus deserticola (Trappe, Bloss, and Menge) increased growth from 394% to 100% over non-inoculated control plants when soil P was low ( 0.2 mmol kg^–1 NaHCO₃-extractable P) at soil saturation extract salinities from 1.1 dS m^–1 to 8.8 dS m^–1. When 0.8 and 1.6 mM P was added no dry weight differences due to VAM were observed, however, K and P concentrations were higher in VAM plants in saline treatments.Glomus fasciculatum (Gerdeman and Trappe) andGlomus mosseae (Nicol. and Gerd.) isolates increased growth of VAM tomato 44% to 193% in non-sterilized, saline soil (10 dS m^–1 saturation extract) despite having little effect on growth in less saline conditions when soil P was low. Higher tomato water potentials, along with improved K nutrition by VAM in onion, indicate mechanisms other than increased P nutrition may be important for VAM plants growing under saline stress. These effects appear to be secondary to the effects of VAM on P uptake.     

The K/Na and Ca/Na ratios and rapeseed yield,under soil salinity or sodicity

Rapeseed (Brassica napus) is a crop relatively tolerant to salt and sodium. Our objective was to study the interactions between Na, K and Ca and their relationship with its yield under the isolated effects of soil salinity or sodicity.Two experiments were carried out using pots filled with the Ah horizon of a Typic Natraquoll. There were three salinity levels (2.3 dS m^-1; 6.0 dS m^-1 and 10.0 dS m^-1) and three sodicity levels, expressed as sodium adsorption ratios (SAR: 12; 27 and 44). The soil was kept near field capacity.As soil salinity increased, the K/Na and Ca/Na ratios in the tissues decreased markedly but yields and aerial biomass production were not affected. As soil SAR value increased, the K/Na and Ca/Na ratios in plants and K-Na and Ca-Na selectivities decreased. Plants could not maintain their Ca concentration in soil with a high SAR. The grain yield and biomass production diminished significantly in the highest SAR treatment. Our results are consistent with those showing detrimental osmotic effects of salts in Brassica napus. Conversely, under sodicity, the K/Na and Ca/Na ratios in plant tissues decreased considerably, in accordance with grain and biomass production. These results show that the effects of sodicity are different from those of salinity.