flower species is a suitable candidate for saline water reuse systems. Stock ( Matthiola incana ), a relatively salt-tolerant species, produced marketable stems under irrigation with saline solutions ranging from 2 to 11 dS·m −1 amended with substrate N
Catherine M. Grieve, James A. Poss, Peter J. Shouse, and Christy T. Carter
Genhua Niu, Denise S. Rodriguez, Lizzie Aguiniga, and Wayne Mackay
Use of recycled water to irrigate urban landscapes and nursery plants may be inevitable as fresh water supplies diminish and populations continue to grow in the arid and semiarid southwestern United States. Lupinus havardii Wats. (Big Bend bluebonnet) has potential as a cut flower and Lupinus texensis Hook. (Texas bluebonnet) as a bedding plant, but little information is available on salt tolerance of these species. A greenhouse study was conducted to characterize the growth in response to various salinity levels. Plants were grown in 10-L containers and drip-irrigated with synthesized saline solutions at electrical conductivity levels of 1.6, 3.7, 5.7, 7.6, or 9.4 dS·m−1. Although shoot growth of L. texensis was reduced as salinity levels increased, it was visually acceptable (without any visual injury) when irrigated with salinity levels of less than 7.6 dS·m−1. All plants survived at 7.6 dS·m−1, whereas only 15% did at 9.4 dS·m−1. In contrast, L. havardii had leaf injury at 5.7 dS·m−1. No plants survived at 9.4 dS·m−1, and only 7% plants survived at 7.6 dS·m−1. In addition, growth of L. havardii was significantly reduced and plants were shorter at elevated salinity levels. Cut raceme yield of L. havardii decreased at salinity levels greater than 3.7 dS·m−1. However, no difference in cut raceme yield was observed between the control and 3.7 dS·m−1, although shoot growth was reduced. Overall, L. texensis was more salt-tolerant than L. havardii.
Genhua Niu, Denise S. Rodriguez, and Lissie Aguiniga
Salt-tolerant landscape plants are needed for arid and semiarid regions where the supply of quality water is limited and soil salinization often occurs. This study evaluated growth, chloride (Cl) and sodium (Na) uptake, relative chlorophyll content, and chlorophyll fluorescence of three rose rootstocks [Rosa ×fortuniana Lindl., R. multiflora Thunb., and R. odorata (Andr.) Sweet] irrigated with saline solutions at 1.6 (control), 3.0, 6.0, or 9.0 dS·m−1 electrical conductivity in a greenhouse. After 15 weeks, most plants in 9.0 dS·m−1 treatment died regardless of rootstock. Significant growth reduction was observed in all rootstocks at 6.0 dS·m−1 compared with the control and 3.0 dS·m−1, but the reduction in R. ×fortuniana was smaller than in the other two rootstocks. The visual scores of R. multiflora at 3.0 and 6.0 dS·m−1 were slightly lower than those of the other rootstocks. Rosa odorata had the highest shoot Na concentration followed by R. multiflora; however, R. multiflora had the highest root Na concentration followed by R. odorata. All rootstocks had higher Cl accumulation in all plant parts at elevated salinities, and no substantial differences in Cl concentrations in all plant parts existed among the rootstocks, except for leaf Cl concentration in R. multiflora, which was higher than those in the other two rootstocks. The elevated salinities of irrigation water reduced the relative chlorophyll concentration, measured as leaf SPAD readings, and maximal photochemical efficiency of photosystem II (PSII) and minimal fluorescence (Fo)/maximum fluorescence (Fv/Fm), but the largest reduction in Fv/Fm was only 2.4%. Based on growth and visual quality, R. ×fortuniana was relatively more salt-tolerant than the other two rootstocks and R. odorata was slightly more salt-tolerant than R. multiflora.
Genhua Niu, Denise Rodriguez, and Mengmeng Gu
Texas mountain laurel (Sophora secundiflora) is a native shrub tolerating drought, heat, windy conditions, and alkaline or wet soils. However, its availability is somewhat low and little information is available on nutrient requirement and other culture information. Two greenhouse experiments were conducted to quantify the responses of Texas mountain laurel to different forms and rates of nitrogen (N) fertilizer. In Expt. 1, 1-year old seedlings were treated for 194 days with three NO3:NH4 ratios at 25:75, 50:50, and 75:25 and two rates of N at 100 and 200 mg·L−1 in a factorial design. There was no interaction between the N rate and form on any growth parameters. Nitrogen form did not significantly affect shoot dry weight, root dry weight, root–to-shoot ratio, or the total dry weight. There was no significant difference between N rate of 100 and 200 mg·L−1 on root dry weight, root-to-shoot ratio, or the total dry weight. The shoot dry weight of Texas mountain laurel fertilized with 100 mg·L−1 was higher compared with that of the plants fertilized at 200 mg·L−1. The reduced shoot dry weight at N of 200 mg·L−1 was the result of the higher substrate salinity. In Expt. 2, seedlings were fertilized with five N rates (50, 100, 150, 200, and 250 mg·L−1) for 203 days. Plants watered with 150, 200, and 250 mg·L−1 were taller than those fertilized with 50 mg·L−1. The shoot height of plants watered with 100 mg·L−1 was only significantly different from 50 mg·L−1. For rapid growth of Texas mountain laurel, a N rate range of ≈150 mg·L−1 was recommended supplied with a combination of NO3-N and NH4-N in the ratios of 0.3 to 3.0.
Genhua Niu, Terri Starman, and David Byrne
The responses of garden roses to irrigation water with elevated salts are unknown. Two experiments were conducted to evaluate the relative salt tolerance of 13 self-rooted rose cultivars by irrigating the plants with nutrient solutions at an electrical conductivity (EC) of 1.4 dS·m−1 (control) or nutrient saline solutions at EC of 3.1, 4.4, or 6.4 dS·m−1. In Expt. 1, ‘Belinda’s Dream’, ‘Caldwell Pink’, ‘Carefree Beauty’, ‘Folksinger’, ‘Quietness’, and ‘Winter Sunset’ plants were grown in a greenhouse from 13 Aug. to 21 Oct. (10 weeks). Shoot dry weight of all cultivars decreased as EC of irrigation water increased. ‘Winter Sunset’ was most sensitive among these cultivars to salt stress followed by ‘Carefree Beauty’ and ‘Folksinger’ with severe leaf injury at EC of 3.1 dS·m−1 or higher or death at EC of 6.4 dS·m−1. No visual damage was observed in ‘Belinda’s Dream’ or ‘Caldwell Pink’, regardless of the salinity level. In Expt. 2, ‘Basye’s Blueberry’, ‘Iceberg’, ‘Little Buckaroo’, ‘The Fairy’, ‘Marie Pavie’, ‘Rise N Shine’, and ‘Sea Foam’ plants were grown in the greenhouse from 29 Sept. to 16 Nov. (7 weeks) and irrigated with the same nutrient or nutrient saline solutions. Salinity treatment did not affect shoot dry weight of ‘Basye’s Blueberry’, ‘Little Buckaroo’, ‘Sea Foam’, and ‘Rise N Shine’. Shoot dry weight of ‘Iceberg’, ‘The Fairy’, and ‘Marie Pavie’ decreased as EC of irrigation water increased. No or little visual damage was observed in ‘Little Buckaroo’, ‘Sea Foam’, and ‘Rise N Shine’. Leaf tip burns were seen in ‘Iceberg’, ‘Marie Pavie’, ‘Basye’s Blueberry’, and ‘The Fairy’ at EC 6.4 of dS·m−1. Generally, these symptoms were less severe than those observed in Expt. 1, probably attributable partially to the shorter treatment period. Whereas shoot Na+ and Cl– varied greatly among the rose cultivars, the shoot concentrations of Ca2+, K+, and Mg2+ did not. Generally, salinity-tolerant cultivars had higher shoot Na+ and Cl– concentrations. In summary, in Expt. 1, ‘Belinda’s Dream’ was the most tolerant cultivar, whereas ‘Winter Sunset’ was the least tolerant followed by ‘Carefree Beauty’. In Expt. 2, ‘Iceberg’, ‘Marie Pavie’, and ‘The Fairy’ were less tolerant to salinity as compared with other cultivars, although the differences were small.
Maycon Diego Ribeiro, Rhuanito Soranz Ferrarezi, and Roberto Testezlaf
We evaluated the performance and determined the efficiency parameters of an automated subirrigation system in a commercial greenhouse facility for clonal eucalyptus (Eucalyptus sp.) seedling production to improve subirrigation management practices. A methodology based on the mass balance of the irrigation system was established to determine the volumes of nutrient solution (NS) applied, drained, stored, evapotranspirated, and leaked in each subirrigation bench. The application, drainage, and NS dwell time in the 55-cm3 conic containers (0.125 m height × 0.03 m diameter) and the depth of NS reached inside the bench were also assessed. The values of application efficiency, irrigation efficiency and system transport (supply and drainage), and disposal losses of NS were estimated for each bench and inferred for the entire subirrigation system. The benches had average application and irrigation efficiency values of 0.84% and 98.38%, respectively. The system showed irrigation efficiency values of 27.59% and the sum lost by transport, leakings, and disposal in the water treatment plant of 72.41%. The continuous return of NS because of the high irrigation frequency contributed to this loss, resulting in 10,070 L of NS consumed by the plants and 26,430 L lost after 15 days of cultivation. Our results demonstrated that the system presented an adequate irrigation efficiency, but a low application efficiency caused by the constant return of NS because of the high irrigation frequency and the excess of losses from leaking and disposal of NS after 15 days of cultivation. Nevertheless, the system operated like a hydroponic system, which kept the containers partially immersed in the NS and did not use the full substrate container capacity to provide adequate moisture. This reduced the overall system irrigation and the substrate storage efficiencies, which needs to be improved by proper equipment design, operation, water and nutrients use efficiency, and management to achieve all the benefits that subirrigation possess.
Yuhung Lin and Yaling Qian
Golf courses in the western United States increasingly are being irrigated with recycled water. Research was conducted on eight golf courses in a semiarid region, including three courses with recycled water irrigation for 10 years, three courses with recycled water irrigation for 18 to 26 years, and two courses with surface water for irrigation for 15 and 18 years. Turf quality of kentucky bluegrass (Poa pratensis) (KBG), the most widely used turfgrass species in the United States, was evaluated on 25 roughs from the aforementioned golf courses. Concurrently, KBG shoot samples and soil samples from these sites were collected. Shoots of KBG were analyzed for mineral concentrations, including sodium (Na), calcium (Ca), magnesium (Mg), potassium (K), chlorine (Cl), boron (B), sulfur (S), phosphorus (P), manganese, iron, zinc, copper, and molybdenum. Electrical conductivity (EC) and sodium absorption ratio (SAR) of soil saturated paste were determined. Recycled water irrigation for 10 and >18 years increased clipping Na by 4.3 and 9.9 times and Cl by 1.5 and 1.3 times, respectively. Compared with surface water irrigation, B concentration in KBG shoots increased by 3.5 times and K concentration reduced by 16% on sites with recycled water irrigation for >18 years. Multiple regression analysis was conducted to identify the relationships between mineral concentration in shoots and turf quality. There was a negative linear relationship between turf quality and Na concentration in the shoots (R 2 = 0.65). Soil SAR in 0 to 20 cm depth was highly associated with KBG shoot Na, as documented by a logarithmic regression of R 2 = 0.70. Stepwise regression indicated that Na accumulation in the shoots was the leading plant variable causing the decline of turf quality under recycled water irrigation. Therefore, it is reasonable to believe that water treatment and management practices that can reduce soil SAR and Na concentration in KBG shoots would improve turf quality and plant health.
Genhua Niu and Denise S. Rodriguez
Use of recycled water to irrigate urban landscapes may be inevitable, because the freshwater supply has been diminishing and the population continues to grow in the arid and semiarid southwestern United States. However, little information exists on the performance of landscape plants irrigated with nonpotable water. Two greenhouse studies were conducted during the summer and the fall to characterize the relative salt tolerance of five herbaceous perennials by irrigating the plants with a saline solution at an electrical conductivity (EC) of 0.8 dS·m–1 (tap water), 2.0 dS·m–1, or 4.0 dS·m–1. In the summer study, after 10 weeks of treatment, Achillea millefolium L., Gaillardia aristata Foug., and Salvia coccinea Juss ex J. had an aesthetically acceptable appearance for landscape performance (visual quality scores of 4 points or more), whereas Agastache cana (Hook.) Woot. & Standl. and Echinacea purpurea (L.) Moench had relatively low tolerance to salinity. Dry weight of shoots of A. millefolium, A. cana, and G. arstata was lower at elevated salinity levels. In the fall study, A. millefolium, E. purpurea, G. arstata, and S. coccinea had acceptable growth and visual quality at elevated salinity levels, whereas A. cana had lower quality and reduced growth. Dry weight of shoots was lower in G. arstata and A. millefolium at an EC of 2.0 dS·m–1 or 4.0 dS·m–1. Leaf osmotic potential of all species in the summer experiment was significantly lower at higher salinity compared with the control. In the fall experiment, leaf osmotic potential in A. millefolium, E. purpurea, and G. aristata at 4 dS·m–1 was lower compared with lower salinity treatment and the control. Leaf osmotic potential in the fall was higher than that of the same species at the same salinity level in the summer experiment, indicating that plants in the fall were less stressed than in the summer. Combined the results from both experiments, the authors concluded that A. millefolium, G. arstata, and S. coccinea had a relatively high salt tolerance (as much as 4 dS·m–1 of irrigation water under greenhouse conditions) among the tested species, whereas A. cana and E. purpurea were not tolerant to salt and should not be irrigated with low-quality water.
Iryna Andrenko, Thayne Montague, Cynthia McKenney, and Russell Plowman
Water quality and quantity are critical issues in the Southwest United States and many other locations in the world. Use of reclaimed water for landscape irrigation can conserve potable water significantly and possibly reduce fertilizer application. A potential concern of using alternative water sources is elevated salt levels, which can have adverse effects on plant growth and aesthetic appearance. Most Texas native wildflowers are known to be hardy and easy to maintain, and are drought tolerant after establishment. In addition, native wildflowers provide wildlife habitat and support native pollinators. However, little information is available on salinity tolerance of many Texas native wildflower species. In this study, two separate hydroponic experiments were conducted to determine salt tolerance of three Texas native wildflower species: Gaura villosa Torr. (wooly gaura), Xanthisma texanum DC. (Texas sleepy daisy), and Ipomopsis rubra (L.) Wherry (standing cypress). Species were suspended in a hydroponic setting using a randomized complete block design with a control [municipal reverse-osmosis (RO) water with a nutrition solution at an electrical conductivity (EC) of 3.0 dS·m–1] and three salinity treatments: 5.0, 7.0, and 11.0 dS·m–1 EC. Sixty days after salinity treatments were initiated, percent survival, visual rating, fresh weight, and length measurements were recorded on root and shoot tissue. To determine tissue percentage sodium (Na+), calcium (Ca2+), and chloride (Cl–), shoot and root tissues were dried and ground for tissue analysis. At the end of each experiment, total percent survival for X. texanum, G. villosa, and I. rubra were 100%, 94%, and 76%, respectively, with the greatest mortality rate at the highest salinity treatment. Shoot dry weight and plant growth index (PGI) decreased in all three species as salinity of irrigation water increased. Visual qualities of all species were mainly compromised at the highest salinity level. Ion concentrations in root and shoot tissues were affected by salinity levels and varied among species. Different mechanisms of salt tolerance (ion exclusion, salt excretion, and tissue tolerance to high concentrations of Na+ or Cl–) have been observed among wildflower species, and results indicate different salt tolerance mechanisms were exhibited by each trial species. In addition, results indicate I. rubra can be identified as moderately salt tolerant (EC up to 7.0 dS·m–1), whereas, X. texanum and G. villosa can be classified as salt tolerant (EC up to 11.0 dS·m–1). Results from this study suggest great potential of these native Texas wildflowers in landscapes using limited-quality irrigation water or landscapes with soil salinity concerns.
Laura A. Warner, Alexa J. Lamm, Peyton Beattie, Sarah A. White, and Paul R. Fisher
rainfall intercepted by the property in a catchment basin or tanks for irrigation use water reuse: capture of excess irrigation water in a catchment basin or tank for reapplication to subsequent crops microirrigation: limited coverage drip and spray