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  • Author or Editor: Catherine M. Grieve x
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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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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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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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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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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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Marigolds are one of the most popular annual ornamental plants; both, the short-stature cultivars (Tagetes patula L.) and the taller cultivars (T. erecta L.) are used as container plants in landscape and garden settings. Tagetes erecta varieties can also make excellent cut and dried flowers for the florists' market. The present study was conducted to evaluate the response of T. patula ‘French Vanilla’ and T. erecta ‘Flagstaff’ and ‘Yellow Climax’ to irrigation with saline water with and without pH control. Marigold plugs were transplanted into greenhouse sand tanks and established for 1 week under nonsaline conditions. Ten treatments were then applied with electrical conductivities of irrigation water (ECw) of 2, 4, 6, 8, and 10 dS·m−1 and pH levels of 6.4 and 7.8. Growth of all three cultivars decreased in response to irrigation with saline waters at pH 6.4. Compared with the nonsaline controls, ‘French Vanilla’ exhibited a 20% to 25% decrease in plant height, leaf dry weight (DW), and shoot DW when irrigated with 4 dS·m−1 water. However, the number of flowering shoots and the diameter and number of flowers were not significantly affected until the ECw exceeded 8 dS·m−1. Growth of ‘Flagstaff’ and ‘Yellow Climax’ also decreased as ECw increased. Shoot DW of the tall cultivars decreased by 30% and 24%, respectively, in response to the 4 dS·m−1 treatment, but additional salt stress had no further effect on DW production. Marigolds were highly sensitive to high pH. Plants irrigated with nonsaline water with pH at 7.8 exhibited a 50%, 89%, and 84% reduction in shoot DW in ‘French Vanilla’, ‘Flagstaff’, and ‘Yellow Climax’, respectively, compared with plants irrigated with water with pH 6.4. Marigold cultivars were rated as moderately tolerant to salinity because growth was affected when water ECw exceeded 8 dS·m−1. Salinity tended to reduce internode elongation, resulting in attractive plants. Compactness was not increased as a result of a decrease in DW, resulting in attractive plants, which show great promise as bedding or landscape plants in salt-affected sites provided that the pH of the soil solutions remains acidic. Under our experimental conditions in the sand tank system, the ECw was essentially equivalent to those of the sand soil solution; however, considering that the EC of the sand soil solution is ≈2.2 times the EC of the saturated soil extract (ECe), our salinity treatments may be estimated as 0.91, 1.82. 2.73, 3.64, and 4.55 dS·m−1. Thus, the threshold ECw at which marigold cultivars exhibited acceptable growth, 8 dS·m−1, would be equivalent to ECe of 3.64 dS·m−1.

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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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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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Common stock flower production can be achieved under moderate levels of salinity and relatively low levels of nitrogen with no significant decrease in quality in a closed-recirculating irrigation system. A 4 × 4 factorial design with partial replication was used to assess the effects of salinity and nitrogen on the production of Matthiolaincana (L.). Seeds were sown in outdoor volumetric lysimeters at the George E. Brown, Jr., Salinity Laboratory in Riverside, Calif., with target electrical conductivity (EC) levels of 2, 5, 8, and 11 dS·m–1 combined with four nitrogen treatments of 35, 50, 75, and 100 ppm N. An empirical model was implemented to evaluate the growth response of each combination of salinity and nitrogen treatments over the course of plant development. The three-phase model is represented by an initial size parameter (alpha), an estimation of the intrinsic growth rate of the exponential phase (beta), a transitional phase between the first two phases (tl), the length of the linear phase (epsilon), and the final intrinsic saturation rate (gamma), The model successfully fitted the plant height data over time for all 16 nitrogen and salinity treatment combinations. Effects of salinity on epsilon and t2 (epsilon + t1) were nonsignificant. Nitrogen treatments had no significant effect on any of the model parameters and the effect of salinity was greatest when irrigation water EC was 11 dS·m–1. The length of the flower-bearing stems exceeded the standards recommended for commercial acceptability in all treatments (>41 cm). If 60 cm is the minimum length acceptable, then 50 ppm N or more where the EC was 8 dS·m–1 or less is required. Nitrogen uptake per unit evapotranspiration increased with salinity and nitrogen.

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