Saline Irrigation Affects Growth and Leaf Tissue Nutrient Concentration of Three Native Landscape Plant Species

Abstract

<jats:p>Greywater is a renewable irrigation alternative to potable water; however, its use as an irrigation source is limited by the potential for salt injury to plants. Research was conducted to determine salt tolerance of three common landscape species, small anise tree (<jats:italic>Illicium parviflorum</jats:italic>), ‘Henry’s Garnet’ sweetspire (<jats:italic>Itea virginica</jats:italic>), and muhly grass (<jats:italic>Muhlenbergia capillaris</jats:italic>). Two experiments were performed, one with high sodium chloride (NaCl) concentrations and one with low NaCl concentrations. Plants received daily irrigation of tap water containing one of the following NaCl concentrations: 0 (tap water); 2000, 4000, 6000, 8000, or 10,000 mg·L<jats:sup>−1</jats:sup> (high NaCl); or 0 (tap water), 250, 500, or 1000 mg·L<jats:sup>−1</jats:sup> (low NaCl) for 15 weeks. Plants were harvested after 5, 10, or 15 weeks. Root dry weight (RDW) and shoot dry weight (SDW) were determined at each harvest; survival was determined at experiment termination. Leaf tissue was analyzed for tissue macronutrient [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and, magnesium (Mg)], sodium (Na), and chlorine (Cl) concentrations in the high NaCl concentration experiment. With high NaCl, RDW and SDW decreased with increasing NaCl for all species. Anise and sweetspire had low or no survival, respectively, at the highest NaCl concentration; muhly grass had 100% survival regardless of treatment. In general, leaf macronutrient, Na, and Cl increased with increasing NaCl concentration. With low NaCl, there was no effect of NaCl concentration on RDW or SDW for all species. All three species continued to grow between harvest dates in the lower NaCl concentration experiment, whereas only anise and muhly grass continued to grow with high NaCl. Anise and muhly grass were tolerant of saline irrigation that could be expected from greywater. Sweetspire exhibited symptoms of salt stress (necrotic leaves and leaf drop, visual observation) at all NaCl concentrations including the lowest (250 mg·L<jats:sup>−1</jats:sup>), and should not be irrigated with saline water.</jats:p>

Growth, Gas Exchange, and Mineral Nutrients of Ornamental Grasses Irrigated with Saline Water

“…To the best of our knowledge, there were no reports of the leaf Na + concentrations of E. spectabilis and S. scoparium irrigated with saline water irrigation. However, the values recorded in our study were much less than those reported by LeCompte et al (2016), who found that pink muhly grass had 11.7 to 31.4 mg • g -1 Na + in the leaves when grown in a substrate (5 pinebark:3 peat:1 perlite) and irrigated with 4000 to 10,000 mg • L -1 NaCl (5.0-12.5 dS • m -1 ) for 15 weeks. The discrepancy in the leaf Na + concentrations in these studies might result from different plant species and different durations of saline water irrigation.…”

“…Pink muhly grass irrigated with 2000 to 4000 mg • L -1 NaCl (EC, 2.5-5.0 dS • m -1 ) had 15.6 to 17.4 mg • g -1 Clions in the leaves (LeCompte et al, 2016). These values are similar to or slightly greater than our results.…”

“…4A). It was not surprising to see this result because previous studies have observed that increasing salinity stress inhibited plant growth and development of ornamental grasses significantly (Alvarez, 2006;LeCompte et al, 2016;Zhang et al, 2012).…”

“…These values are similar to or slightly greater than our results. M. sinensis (accession JM0099) watered with saline solution at an EC of 3.2, 6.1, and 10.5 dS • m -1 accumulated about 28.4, 32.0, and 49.7 mg • g -1 Clions in the leaves (Sun et al, 2015b), whereas pink muhly grass irrigated with 6000 to 10,000 mg • L -1 NaCl (EC, 7.5-12.5 dS • m -1 ) had 47.6 to 60.7 mg • g -1 Clions in the leaves (LeCompte et al, 2016). The values in these studies are much greater than our observations.…”

“…(kikuyugrass) is a suitable candidate for the saline-sodic water reuse system with a threshold EC e of 8.0 dS • m -1 (Grieve et al, 2004(Grieve et al, , 2012. Pink muhly grass can survive at sodium chloride (NaCl) irrigation rates of 10,000 mg • L -1 (corresponding to an EC of 12.5 dS • m -1 ), which is up to 20 times greater than graywater (Christova-Boal et al, 1996;LeCompte et al, 2016). Because diverse ornamental grasses are produced by the green industry, further research is needed to identify salt-tolerant ornamental grasses for landscape use.…”