The degradation of existing freshwater resources and variations in rainfall patterns are straining water resources needed for a growing population. Recycled irrigation water, although often high in salinity, is becoming a more prevalent solution for irrigating landscapes (Devitt et al., 2004). However, irrigating with saline water could suppress plant growth and production (Parida and Das, 2005). According to the two-phase plant growth response to salinity stress explained by Munns (1993), the first phase of growth reduction occurs due to the increase in salinity level in the soil, causing the water to move from the roots to the soil due to the difference in osmotic pressure. In the second phase, sodium (Na+) or chloride (Cl–) ions may enter the transpiration stream, causing an increase in salt concentration in the cell wall or cytoplasm leading to cell injury (Munns, 1993).
Golf courses are one of the sites that use reclaimed or recycled water for irrigation (Harivandi, 2004). Approximately 12% of golf courses in the United States use recycled water for irrigation, and one of the reasons for not using recycled water is the possibility of low-quality turfgrass due to increased concentrations of salts (Throssell et al., 2009a). In contrast to many other areas of agriculture, turfgrass managers are primarily concerned with turfgrass quality and aesthetics rather than overall yield (Breuninger et al., 2013).
Salt glands that help in the excretion of excess Na+ and Cl– ions have been reported in turfgrasses (Liphschitz and Waisel, 1974; Marcum and Murdoch, 1990). These glands helped in the excretion of salts, and the rate of excretion indicated the level of salinity tolerance of grasses in the subfamily Chloridoidea (Marcum, 1999). Bermudagrass (Cynodon sp.), belonging to the Chloridoidea, is one of the most important and widely adapted warm-season turfgrasses. Bermudagrasses have shown moderate salinity tolerance when subjected to varying concentrations of salinity (Marcum and Murdoch, 1994). Past research conducted on bermudagrass and other turfgrass species reported decreasing visual parameters of percent green cover, turf quality (TQ), and leaf firing (LF) (Xiang et al., 2017, 2018), in addition to plant growth measurement, as plant salinity stress increases (Alshammary et al., 2008; Marcum, 1999; Uddin et al., 2011, 2012). Because the increase in LF is based on the change in color of the leaves, LF can indicate injury in the plant due to salinity stress.
Human evaluation of LF and TQ requires adequate training, consistency, and time (Bell et al., 2002a; Trenholm et al., 1999). Some of the alternative techniques to visual ratings are digital image analysis and the NDVI, which can provide a quantitative assessment of the magnitude of stress (Bell et al., 2002a; Sonmez et al., 2008). A strong correlation between NDVI and human evaluation of TQ and LF was reported for both clonal and common bermudagrass (Cynodon dactylon) in response to salinity stress (Xiang et al., 2017, 2018). Therefore, implementing digital image analysis or spectral reflectance techniques may be more efficient and consistent to reduce human variability when screening turfgrass species and cultivars for salinity tolerance.
Few studies have evaluated the salinity stress of bermudagrass using NDVI as the primary indicator of salinity stress applied via overhead watering. Overhead watering is most similar to industry practices and would expose all plant parts, including leaves, to salinity stress (Koch and Bonos, 2010). Also, no previous research has been conducted to understand the response of common bermudagrass cultivars to a larger number of treatments with smaller increments. Most studies in the past have used limited salinity treatments with larger increments, which resulted in a linear response (Marcum and Murdoch, 1990; Uddin et al., 2012; Xiang et al., 2017). However, small increments in salinity concentration may result in a nonlinear response. Therefore, the objective of this research is 1) to evaluate the response of ‘Riviera’ common bermudagrass when irrigated with 12 salinity treatments (4–48 dS·m−1) in increments of 4 dS·m−1 and control via manual overhead irrigation for 30 d, 2) to evaluate NDVI as a tool for validating visual ratings of salinity stress, and 3) to determine whether the smaller increments of salinity treatments resulted in a nonlinear response.
Alshammary, S.F., Hussain, G. & Qian, Y.L. 2008 Response of four warm-season grasses to saline irrigation water under arid climate Asian J. Plant Sci. 7 619 627 doi: 10.3923/ajps.2008.619.627
Bell, G.E., Martin, D.L., Wiese, S.G., Dobson, D.D., Smith, M.W., Stone, M.L. & Solie, J.B. 2002a Vehicle-mounted optical sensing: An objective means for evaluating turfgrass quality Crop Sci. 42 197 201 doi: 10.2135/cropsci2002.1970
Breuninger, J.M., Welterlen, M.S., Augustin, B.J., Cline, V. & Morris, K. 2013 The turfgrass industry, p. 37–104. In: J.C. Stier, B.P. Horgan, and S.A. Bonos (eds.). Turfgrass: Biology, use, and management. Amer. Soc. Agron., Crop Sci. Soc. Amer., Soil Sci. Soc. Amer., Madison, WI. doi: 10.2134/agronmonogr56.c2
Devitt, D., Morris, R., Kopec, R.D. & Henry, M. 2004 Golf course superintendents’ attitudes and perceptions toward using reuse water for irrigation in the southwestern United States HortTechnology 14 577 583 doi: 10.21273/HORTTECH.14.4.0577
Dudeck, A.E., Singh, S., Giordano, C.E., Nell, T.A. & McConnell, D.B. 1983 Effects of sodium chloride on Cynodon turfgrasses Agron. J. 75 927 930 doi: 10.2134/agronj1983.00021962007500060017x
Guimaraes, F.V.A., Lacerda, C.F., Marques, E.C., Abreu, C.E.B., Aquino, B.F., Prisco, J.T. & Gomes-Filho, E. 2012 Supplemental Ca2+ does not improve growth but it affects nutrient uptake in NaCl-stressed cowpea plants Braz. J. Plant Physiol. 24 9 18 doi: 10.1590/S1677-04202012000100003
Harivandi, M.A. 2004 A review of sports turf irrigation with municipal recycled water Acta Hort. 661 131 136 doi: 10.17660/ActaHortic.2004.661.16
Horst, G.L., Engelke, M.C. & Meyers, W. 1984 Assessment of visual evaluation techniques Agron. J. 76 619 622 doi: 10.2134/agronj1984.00021962007600040027x
Koch, M.J. & Bonos, S.A. 2010 An overhead irrigation screening technique for salinity tolerance in cool-season turfgrasses Crop Sci. 50 2613 2619 doi: 10.2135/cropsci2010.03.0134
Liphschitz, N. & Waisel, Y. 1974 Existence of salt glands in various genera of the Gramineae New Phytol. 73 507 513 doi: 10.1111/j.1469-8137.1974.tb02129.x
Marcum, K.B. & Murdoch, C.L. 1990 Growth responses, ion relations, and osmotic adaptations of eleven C4 turfgrasses to salinity Agron. J. 82 892 896 doi: 10.2134/agronj1990.00021962008200050009x
Marcum, K.B. & Murdoch, C.L. 1994 Salinity tolerance mechanisms of six C4 turfgrasses J. Amer. Soc. Hort. Sci. 119 779 784 doi: 10.21273/JASHS.119.4.779
Marcum, K.B. 1999 Salinity tolerance mechanisms of grasses in the subfamily Chloridoideae Crop Sci. 39 1153 1160 doi: 10.2135/cropsci1999.0011183X003900040034x
Marcum, K.B., Pessarakli, M. & David, M.K. 2005 Relative salinity tolerance of 21 turf-type desert saltgrasses compared to bermudagrass HortScience 40 827 829 doi: 10.21273/HORTSCI.40.3.827
Marcum, K.B. & Pessarakli, M. 2006 Salinity tolerance and salt gland excretion efficiency of bermudagrass turf cultivars Crop Sci. 46 2571 2574 doi: 10.2135/cropsci2006.01.0027
Morris, K.N. & Shearman, R.C. 2008 NTEP turfgrass evaluation guidelines. 15 Dec. 2019. <http://www.ntep.org/reports/ratings.htm>
Munns, R. 1993 Physiological processes limiting plant growth in saline soil: Some dogmas and hypotheses Plant Cell Environ. 16 15 24 doi: 10.1111/j.1365-3040.1993.tb00840.x
Parida, A.K. & Das, A.B. 2005 Salt tolerance and salinity effects on plants: A review Ecotoxicol. Environ. Saf. 60 324 349 doi: 10.1016/j.ecoenv.2004.06.010
Sonmez, N.K., Emekli, Y., Sari, M. & Bastug, R. 2008 Relationships between spectral reflectance and water stress conditions of bermudagrass (Cynodon dactylon L.) N. Z. J. Agr. Res. 51 223 263 doi: 10.1080/00288230809510451
Throssell, C.S., Lyman, G.T., Johnson, M.E., Stacey, G.A. & Brown, C.D. 2009a Golf course environmental profile measures water use, source, cost, quality, and management and conservation strategies Appl. Turfgrass Sci. 6 1 20 doi: 10.1094/ATS-2009-0129-01-RS
Trenholm, L.E., Carrow, R.N. & Duncan, R.R. 1999 Relationship of multispectral radiometry data to qualitative data in turfgrass research Crop Sci. 39 763 769 doi: 10.2135/cropsci1999.0011183X003900030025x
Uddin, M.K., Juraimi, A.S., Ismail, M.R., Othman, R. & Rahim, A.A. 2011 Relative salinity tolerance of warm season turfgrass species J. Environ. Biol. 32 309 312
Uddin, M.K., Juraimi, A.S., Hossain, M.A., Ismail, M.R., Radziah, O. & Rahim, A.A. 2012 Physiological and growth response of tropical turfgrass to salinity stress ScientificWorldJournal 2012 1 10 doi: 10.1100/2012/905468
Xiang, M., Moss, J.Q., Martin, D.L., Su, K. & Dunn, B.L. 2017 Evaluating the salinity tolerance of clonal-type bermudagrass cultivars and an experimental selection HortScience 51 185 191 doi: 10.21273/HORTSCI10773-16
Xiang, M., Moss, J.Q., Martin, D.L., Su, K. & Dunn, B.L. 2018 The salinity tolerance of seeded-type common bermudagrass cultivars and experimental selections HortTechnology 28 276 283 doi: 10.21273/HORTTECH03975-18
Zulkaliph, N.A., Juraimi, A.S., Uddin, K., Ismail, M.R., Ahmad-Hamdani, M.S. & Nahar, U.A. 2013 Screening of potential salt tolerant turfgrass species in peninsular Malaysia Aust. J. Crop Sci. 7 1571 1581