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Christy T. Carter and Catherine M. Grieve

Zinnia elegans, because of its economic value and the hardiness of its wild relatives, was selected as a potential salt-tolerant cut flower crop to grow in greenhouse systems using recycled agricultural wastewater. Using recycled wastewater for irrigation of cut flowers provides an alternative to high-quality water. This is especially important in coastal and inland growing regions of California where competition for high-quality water is increasing between urban and agricultural users and provides economic and environmental benefits because groundwater contamination is reduced or even prevented. A completely randomized design was used to determine the effects of water ionic composition and salinity on the growth and leaf mineral composition of Zinnia elegans. Two cultivars (Benary's Giant Salmon Rose and Benary's Giant Golden Yellow) were grown under irrigation with two different water ionic compositions mimicking dilutions of sea water (SWD) and concentrations of Colorado River water (CRW) at increasing salinity levels with electrical conductivities of 2.5 (control), 4.0, 6.0, 8.0, and 10.0 dS·m−1 in greenhouse sand tanks in Riverside, CA. Leaf mineral concentrations were determined for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chlorine (Cl), total sulfur (S), and total phosphorus (P). At harvest, final plant measurements included time to flowering, stem length, stem diameter (recorded at the soil line), internode length (recorded at the middle of the stem), inflorescence diameter, ray length, plant shoot fresh weight, number of leaves per plant, and number of shoots per plant. For both cultivars, plant tissue concentrations of Mg, Cl, Na, and total S increased as salinity increased in the irrigation water. Conversely, plant tissue concentrations of Ca, K, and total P decreased as salinity increased in the irrigation water. Both cultivars demonstrated high selectivity for K over Na as salinity increased in CRW and SWD with ‘Golden Yellow’ demonstrating a higher selectivity than ‘Salmon Rose’. Additionally, measured growth parameters tended to decrease as salinity increased in both irrigation water types for both cultivars. Stem lengths of 79 cm and 51 cm were found for ‘Salmon Rose' growing in 10 dS·m−1 in concentrations of CRW and SWD, respectively. ‘Golden Yellow' produced stem lengths of 74 cm and 46 cm in 10 dS·m−1 in response to concentrations of CRW and SWD, respectively. Inflorescence diameters of both cultivars approximated 8.0 cm at the highest salinity for both water types. Although significant differences were found, the minimum of 46 cm indicates that marketable flowers can be produced using both water types at least as high as 10 dS·m−1.

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Michael C. Shannon and Catherine M. Grieve

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Catherine M. Grieve, Christy T. Carter* and James A. Poss

Saline wastewaters may provide a valuable water source for the irrigation of selected floriculture crops as demand for quality water increases. A completely randomized design with 3 replications was used to test the effects of salinity on productivity and mineral accumulation on each of two Limonium species grown in greenhouse sand tanks. Three-week-old seedlings (n = 15) of Limonium perezii `Blue Seas' and L. sinuatum `American Beauty' were exposed to 7 salinity treatments (2.5 (control), 7, 11, 15, 20, 25, and 30 dS·m-1) prepared to simulate saline drainage waters of the San Joaquin Valley (SJV) in California. After 10 weeks, vegetative material from five plants from each tank was harvested to assess mineral composition (total-S, total-P, Ca2+, Mg2+, Na+, K+, and Cl-), for each variety. Ion selectivity coefficients were calculated by dividing the ratio of specific ions in the plant by those found in the medium. Stem length and weight, and flower stem numbers were determined at harvest. Salt tolerance thresholds based on stem length for L. perezii and L. sinuatum were 2.5 and 7.0 dS·m-1, respectively. Maximum growth of both species declined as salinity increased, but both species were able to complete their life cycles at 30 dS m-1. L. sinuatum had higher leaf concentrations of Na+, K+, Mg2+, Cl-, and total-P than L. perezii. K+ was preferentially accumulated with regard to Na+ by both species, but was significantly higher in L. sinuatum. Limonium perezii and L. sinuatum can be rated as sensitive and moderately salt tolerant plants, respectively.

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Christy T. Carter, Catherine M. Grieve and James A. Poss

Salinity tolerance of two cultivars of Celosiaargentea (`Chief Rose' and `Chief Gold') was investigated using a completely randomized design with three replications. Seedlings grown in greenhouse sand tanks were exposed to six salinity levels (2.5, 4, 6, 8, 10, and 12 dS·m–1) and two water ionic compositions mimicking sea water and drainage waters from the Imperial and Coachella valleys. Phenotypic measurements were made when plants were harvested during flowering, and concentrations of Ca2+, Mg2+, Na+, K+, Cl-, total-S, and total-P were also determined from leaf tissues. Overall, phenotypic measurements (including stem length, stem weight, stem diameter, inflorescence length, inflorescence weight, and number of leaves) tended to decrease as salinity increased, yet stem lengths were still above the minimum stem length recommended for marketability (41 cm). Significant interactions were found for salinity and water ionic composition for all mineral analyses for both cultivars. As salinity increased, Ca2+, K+, and total-P decreased as Mg2+, Na+, and Cl- increased for both cultivars. `Chief Gold' can be produced commercially in either water composition up to 12 dS·m–1. `Chief Rose' can be produced up to 8 dS·m–1 in sea water and 10 dS·m–1 in water ionic compositions similar to those of the Imperial and Coachella valleys. Saline waters dominated by chloride and sulphate salts can be used to produce Celosiaargentea commercially.

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Catherine M. Grieve, James A. Poss and John H. Draper

To explore the possibility that saline wastewaters may be used to grow high value floriculture crops, the effects of salinity were tested on Helianthus annuus (L.). Sunflower cultivars Sunbeam and Moonbright were grown in 30 greenhouse sand tanks and irrigated initially with nutrient solution. One week after planting, saline treatments were imposed with solutions differing in ion composition. Fifteen tanks were irrigated with waters typical of agricultural wastewaters present in the San Joaquin Valley (SJV) and 15 tanks were irrigated with water compositions similar to saline tailwaters found in the Imperial and Coachella valleys (ICV). Five treatments of each salinity type were used with electrical conductivities (EC) of 2.5, 5, 10, 15, and 20 dS·m–1. Length of the flowering stems was significantly reduced as salinity rose to 20 dS·m–1. Reduction was more pronounced when the plants were irrigated with the sodium-sulfate dominated waters of SJV composition. Flower diameter was reduced when the EC of SJV waters exceeded 15 dS·m–1, but was not affected by any treatment when ICV waters were used. Salt tolerance in sunflower appears to be associated with mechanism(s) that regulate transport of potentially injurious ions. Both Na+and Cl- were partitioned to the lowest portion of the stem, and effectively excluded from the remainder of the shoot. This study illustrates that saline waters with EC = 15 or 20 dS·m–1 may be used to produce ornamental sunflowers without significant loss of quality. Salt stress also provides an environmentally friendly alternative to the use of growth regulators for the control of plant height.

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Catherine M. Grieve, Stacy A. Bonos and James A. Poss

Six selections of Kentucky bluegrass (Poa pratensis L.) cultivars, selected based on their drought tolerance under field and growth chamber conditions in New Brunswick, N.J., were evaluated for salt tolerance based on yield and growth rates at eight soil water salinities [2 (control), 6, 8, 10, 12, 14, 18, and 22 dSm-1] from Apr. to Sept. 2005 in Riverside, Calif. Cultivars Baron and Brilliant were selected as drought sensitive and `Cabernet', `Eagleton', and `Midnight' were selected as drought tolerant. A Texas × Kentucky bluegrass (Poa arachnifera × Poa pratensis) hybrid selection (identified as A01-856) developed for improved drought and heat tolerance was also included. Vegetative clones were established in a randomized complete-block design with three replications, each containing 11 clones. Cumulative biomass and clone diameters were measured over time to evaluate relative yields and growth rates for the six cultivar selections. Based upon maximum absolute biomass production as a function of increasing EC, the order of production was `Baron' > `Brilliant' > `Eagleton' > `Cabernet' ≥ `Midnight' > A01-856. Yield relative to the non-saline control (2 dSm-1) for each cultivar was similar, except that the differences between cultivars were less pronounced, and `Baron' slightly outperformed `Brilliant'. Clone area expansion rates were analyzed with a phasic growth model and beta, the intrinsic growth rate of the exponential phase parameter, significantly varied with salinity. Ranking of cultivars, based on expansion rates, was similar to that based on cumulative biomass. Salinity tolerance in this experiment did not appear to be related to the observed ranking for drought tolerance.

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Michael C. Shannon, Catherine M. Grieve, Scott M. Lesch and John H. Draper

Saline agricultural drainage water may be used as a resource to grow high value horticultural crops and reduce the volume of drainage for eventual disposal. To explore reuse options the effects of salinity and timing of application were tested on selected leafy vegetables grown in 24 sand culture plots in Riverside, Calif. The leafy winter vegetables included `Ruby Red Chard' Swiss chard [Beta vulgaris L. var. flavescens (Lam.) Lam.], `Space' spinach (Spinacia oleracea L.), `Vitamin Green' salad greens [Brassica rapa L. (Narinosa Group)], `Red Giant' mustard greens [Brassica juncea L. (Czerniak)], pac choi [Brassica rapa L. (Chinensis Group)], `Winterbor' kale [Brassica oleracea L. (Acephala Group)], tatsoi [Brassica rapa L. (Narinosa Group)], `Salad King' curly endive (Cichorium endivia L.), and `Red Preco No. 1' radicchio (Cichorium intybus L.). All vegetables were planted at the same time and irrigated initially with tap water and nutrients. At 3 and 7 weeks after seeding (application times), six salinity treatments were initiated by adding salts to the irrigation water to represent the chemical compositions of drainage waters found typically in the San Joaquin Valley, Calif. The six salinity treatments had electrical conductivities of 3 (control), 7, 11, 15, 19, or 23 dS·m-1. A randomized complete block design was used with (6 salinities × 2 application times × 2 replications). Within each plot a 1.5-m row of each of the nine vegetables was grown as split plots. Salinity reduced fresh weight (FW) yields of all species. Salt stress applied at 3 weeks after seeding reduced FWs for seven of the nine vegetables compared to salination at 7 weeks. Analyses of salt tolerance curves, maximum yields, and the point of 50% yield reduction (C50) were conducted. Greens produced the highest biomass at 874 g/plant, but was the most affected by application time. Swiss chard and radicchio were not significantly affected by timing of salinity application, and Swiss chard was the most salt tolerant overall. Greens, kale, pac choi, and to a lesser extent, tatsoi, have potential as winter-grown, leafy vegetables in drainage water reuse systems.

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Stephen R. Grattan, Catherine M. Grieve, James A. Poss, Timothy E. Smith and Donald L. Suarez

High salinity and boron often occur together in irrigation water in arid climates, but very little research has been done to study the interaction of the two. A greenhouse experiment was conducted at the US Salinity Laboratory in sand tanks to evaluate the interactions between B and saline drainage water on the performance of broccoli. Particular interest in this study was directed towards the composition of the salinizing solution to determine what role various salts have on the salinity-boron interaction. Results from this study indicate that both Cl-based salts and those characteristic of saline drainage water (i.e., a mixture of salts dominated by sodium sulfate) showed a significant salinity–boron interaction. At high salinity, increased B concentration was less detrimental, both visually and quantitatively (i.e., biomass), than it was at low salinity. That is, plants could tolerate a higher solution B-concentration at higher salinity. However, there was no significant difference between salt types. The effects on head weights were more exaggerated than those on shoot biomass. Shoot B concentration was influenced by salinity, but interestingly the direction of influence was dependent upon the B concentration in the solution. Regardless of the composition of the salinizing solution, increased salinity increased shoot B concentration when B concentrations in the solution were relatively low (i.e., 0.5 mg·L-1). At the highest solution B concentration (28 mg·L-1), increased salinity reduced shoot B concentration. Solution B in itself had very little influence on shoot ion accumulation, but both salinity (i.e., EC) and salinity composition had very strong influences on shoot tissue ion composition. Therefore, these data indicate that salinity and B are antagonistic.

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James A. Poss, Catherine M. Grieve, Walter B. Russell and Stacy A. Bonos

Six cultivars or selections of Kentucky bluegrass (Poa pratensis L.) exposed to salinity stress were evaluated with ground-based remote sensing plant reflectance (R) measurements at wavelengths ranging from 350 nm to 2500 nm. Cultivars Baron, Brilliant, Cabernet, Eagleton, Midnight, and the selection A01-856, a Texas × Kentucky bluegrass hybrid (Poa arachnifera × P. pratensis), were grown outdoors from vegetative clones in a gravelly-sand medium from Apr. to Sept. 2005, in Riverside, Calif., at soil water salinities ranging from 2 to 22 dSm-1. Two Normalized Difference Vegetation Indicies (NDVI) were developed based on: 1) canopy reflectance in the visible domain at 695 and 670 nm and 2) an average of eight wavelengths in mid-infrared [Ravg = (R:1500, R:1680, R:1740, R:1940, R:2050, R:2170, R:2290, and R:2470 nm/8)] and the reference wavelength (670 nm). Both NDVIs were significantly sensitive to salinity-induced changes in grass canopies and were able to discriminate significantly between the salt-tolerant cultivars (`Baron', `Brilliant', and `Eagleton') and salt-sensitive cultivars (`Cabernet', `Midnight', and A01-856). Another remotely sensed index, based on the derivative of the absorbance (1/R) in the red-edge region between 600 and 800 nm, also generated a similar ranking to the NDVIs and biomass for the six cultivars. These findings indicate that remote sensing of canopy reflectance may represent an additional tool to evaluate and explain the biophysical or physiological differences among Kentucky bluegrass cultivars related to salt tolerance.

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Luis A. Valdez-Aguilar, Catherine M. Grieve, Abdul Razak-Mahar, Milton E. McGiffen and Donald J. Merhaut

Landscape irrigation is the second largest user of reclaimed water in industrialized countries; however, its high concentration of soluble salts, especially Na+ and Cl, may induce growth reduction and leaf necrosis or bronzing in ornamental species. The present study was conducted to determine the growth and quality responses and nutritional ion imbalances of selected landscape species during the container production phase when subjected to irrigation with water of increasing NaCl + CaCl2 concentrations. Plants of boxwood [Buxus microphylla var. japonica (Mull. Arg. ex Miq) Rehder & E.H. Wilson], escallonia (Escallonia ×exoniensis hort. Veich ex Bean), hawthorn [Raphiolepis indica (L.) Lind. Ex Ker Gawl. × ‘Montic’], hibiscus (Hibiscus rosa-sinensis L.), and juniper (Juniperus chinensis L.) were grown in a greenhouse in the Spring–Summer and in the Fall–Winter in separate experiments. Saline irrigation consisted of solutions with electrical conductivities (ECiw) of 0.6, 2, 4, 6, and 8 dS·m−1 in the Spring–Summer experiment and 0.6, 4, 6, 8, and 12 dS·m−1 in the Fall–Winter. Growth of the five species decreased when irrigated with saline waters. Leaf growth was highly sensitive to salinity and the average decrease in leaf dry weight was the criterion used to rank the tolerance of the species. In the Spring–Summer experiment, the ranking was (higher tolerance to lower tolerance): juniper ∼ boxwood > escallonia > hawthorn > hibiscus, whereas in Fall–Winter, the ranking was: juniper ∼ boxwood > hibiscus > escallonia > hawthorn. The species were ranked according to their visual attractiveness in the Spring–Summer experiment. The threshold ECiw at which visual attractiveness was affected gave the following ranking (higher to lower tolerance): hibiscus > juniper > escallonia > hawthorn > boxwood. Estimating the EC of drainage water from threshold ECiw, boxwood was classified as sensitive, hawthorn as moderately sensitive, escallonia as moderately tolerant, and hibiscus and juniper as highly tolerant. Tolerance of juniper was ascribed to Na+ and Cl retention in the roots observed in both growing seasons and to the higher root biomass that allowed a higher accumulation of salts in this organ, preventing translocation to the leaves. Although boxwood exhibited acceptable tolerance in terms of growth, visual quality severely decreased; in contrast, growth of hibiscus was the most severely reduced but was rated as the most tolerant species in terms of visual quality. This opposite response may be the result of an excellent capacity to compartmentalize salts in hibiscus, whereas in boxwood, this mechanism may be absent.