Abstract
Water scarcity is a major problem for crop production around the world including Southwestern United States and growers are increasingly using groundwater for agriculture in Southern New Mexico. Most of the groundwater in New Mexico is brackish and continuous long-term use could lead to salt accumulation in the soil. Reverse osmosis (RO) can desalinate brackish groundwater (BGW), however, environmentally safe disposal of RO concentrate is costly. This greenhouse study evaluated the effects of BGW and RO concentrate at various growth stages of two chile pepper cultivars, NuMex Joe E. Parker and NuMex Sandia Select. Five salinity treatments were applied to plants, three of them used saline waters of 0.6 (control), 4.0 (BGW), and 8.0 dS/m (RO) throughout the growing season, whereas the other two changed waters of 4.0 and 8.0 dS/m to waters of 2.0 and 6.0 dS/m from the beginning of the flowering stage. Number of flowers, days to flowering, relative plant heights, relative fresh biomass, fruit yields, photosynthetic rate (Pn), stomatal conductivity (gS), and actual evapotranspiration (ETa) significantly decreased with increasing irrigation water salinity levels. Concentrations of Mg2+, Na+, and Cl− in plants increased with increasing water salinity levels. Changing to irrigation with reduced salinity waters of 2.0 and 6.0 dS/m at the flowering stage initiated reproductive development more rapidly and alleviated the adverse influence of salinity on the number of flowers of chile pepper, plant height, Pn, as well as fresh shoot and fruit weight than that with continuous irrigation with electrical conductivity (EC) of 4.0 dS/m and 8.0 dS/m beyond the flowering stage. Irrigation that practices a change from high salinity to lower salinity at the flowering stage can optimize the use of saline irrigation water for growing chile peppers.
Salinity and drought are the two major abiotic stress factors for plants and reduce agricultural production in many parts of the world, including Southwestern United States (Niu et al., 2010a). The opportunity to use brackish groundwater (BGW) in the cultivation of vegetable crops needs to be examined because of limited supplies of fresh water in the Southwestern United States, and may assist in enhancing the sustainable development of vegetable crops (Smedema and Shiati, 2002). Unfortunately, the use of brackish water can lead to the accumulation of salts on the soil surface (Duan and Fedler, 2013). Southern New Mexico has a semiarid climate with surface water decreasing due to low precipitation and high evapotranspiration rate. Hence, growers are increasingly using groundwater for irrigation (Baath et al., 2017; Flores et al., 2016). However, underground water resources in this region are mostly of low quality and ∼75% of them are brackish (Lansford et al., 1990). Irrigation with BGW could cause salt stress, associated ion imbalances in crops, and decrease crop growth and yield (Farooq et al., 2015; Munns and Tester, 2008).
Reverse osmosis (RO) is a process that can desalinize BGW, consequently produces high salinity concentration water (UNEP International Environmental Technology Center, 1998). Concentrate water disposal is difficult and expensive. The RO concentrate water might be used as irrigation water in semiarid areas where water is limited (Flores et al., 2015, 2017). However, salt-sensitive plants restrict the use of RO concentrate water and brackish water. A higher leaching fraction (LF) is required for the growth of salt-sensitive plants, and to control the salinity in the root zone (Shannon et al., 1997). Plant height and biomass increased with high LF rate and LFs of ≥0.30 are recommended to control salt distribution and sustain plant growth (Miyamoto et al., 1994; Noaman and El- Haddad, 2000).
The effects of salinity on plant growth and physiological processes depend on the level and duration of exposure to brackish water. Salinity exacerbates osmotic pressure but decreases plant water and nutrient uptake (Ashraf and Wu, 1994; Singh et al., 2014). Increasing salinity in the soil can reduce plant biomass, evapotranspiration, plant growth, and production (Shukla, 2014). Tolerable levels of salinity may not affect leaf photosynthetic rates, though a decrease in photosynthetic rates is noted in an excess of plants’ salinity tolerance (Alvarez et al., 2012; Ge et al., 2014; Koyro et al., 2013). Studies have shown that the tolerance of the salt stress can depend on the plant species, cultivar, and growth stage (Díaz et al., 2013; Maas and Hoffman, 1977; Pasternak and Malach, 1994;). Moreover, climatic conditions, soil type, and irrigation management influence the plant responses to salt stress. Some plant species are more susceptible to salt stress during the first stages of growth, such as emergence, germination, and seedling stage, while others are tolerant at later stages (Ashraf and Foolad, 2007; Katerji et al., 1994; Läuchli and Epstein, 1990; Niu et al., 2010b; Pasternak et al., 1979). It was reported that salt stress induced early flowering in onion (Allium cepa), but it delayed the flowering of tomato (Solanum lycopersicum) (Shannon and Grieve, 1998).
Chile pepper (Capsicum annuum) is an important commercial crop having a large planting area of about 3500 ha in Southwestern United States. The monetary value of New Mexico chile pepper production was estimated at $45 million in 2021 (Bosland and Walker, 2014; Maas and Hoffman, 1977; U.S. Department of Agriculture National Agricultural Statistics Service, 2021). New Mexico is the major producer of chile pepper in the United States. However, chile pepper production in Southern New Mexico is increasingly constrained due to low surface water availability, and available BGW is increasingly used to meet irrigation water shortfalls (Baath et al., 2017; Flores et al., 2016). However, chile pepper is moderately salt-sensitive, and continuous irrigation with BGW could cause yield loss (Baath et al., 2017). A decline in chile pepper yield is observed once EC of irrigation water became greater than 1.5 dS/m, and by the time, EC increased to 5.8 dS/m, chile yield declined by about 50% (Goldberg, 2004; Maas and Hoffman, 1977). However, yield decline was slightly less when chile peppers were irrigated with calcium-rich irrigation waters than NaCl solutions (Baath et al., 2020). Some studies have reported that the germination stage of chile pepper is less sensitive to salinity than the seedling stage (Chartzoulakis and Klapaki, 2000; Niu et al., 2010b). Limited studies have reported the tolerance of different chile pepper genotypes to salinity (Aktas et al., 2006). Therefore, it is essential to evaluate the responses of different cultivars of chile pepper to saline water at different growth stages for sustaining chile production. This study assessed 1) the effects of saline groundwater irrigation on the number of flowers and flowering duration of two chile peppers cultivars, and 2) the relative salt tolerance of two chile pepper cultivars measured by physiological traits, ion uptake, and evapotranspiration.
Materials and Methods
Experimental site and setup.
This experiment was conducted in an environment-controlled greenhouse located at the Fabian Garcia Science Center of New Mexico State University (NMSU), Las Cruces, NM (32.2805° N lat. and 106.7700° W long. at an elevation of 1186 m above sea level). Daily average air temperature and relative humidity in the greenhouse recorded during the whole experiment were 24.0 ± 0.01 °C and 47.0 ± 0.001%, respectively. Soil for the experiment was collected from the Fabian Garcia Science Center of NMSU, air dried, gently crushed, and sieved through a 4-mm sieve. Soil was also sterilized in an oven at a temperature of 80°C for 30 min before packing.
Plastic conic pots (height of 22.3 cm, diameters of 17.5 cm at the base and 25.5 cm at the top, total volume of 8185 cm3) were used in the experiment. The bottom of each pot was covered with cheesecloth to restrain soil loss, and gravel was placed at the bottom to facilitate free drainage. Packing of the soil was done in 4-cm depth increments to obtain a homogeneous profile. The soil bulk density was determined as the ratio of the mass of dry soil to its total volume in the pots (Blake and Hartge, 1986). Particle size analysis using the hydrometer method was accomplished (Gee and Bauder, 1986). According to the United States Department of Agriculture (USDA) textural classification, the soil was a sandy loam (Table 1). Two chile pepper cultivars, NuMex Joe E. Parker and NuMex Sandia Select, were selected for this experiment. Both were transplanted in the pots after 3–5 true-leaf establishment on Feb. 22, 2018, and harvested on May 25, 2018. About 15 g of the Osmocote slow-release fertilizer (14N–6.2P–11.6K, The Scotts Company, USA) was evenly applied to the pots on the day of transplant and during the flowering stage, respectively. The other agronomic managements were the same for all pots.
Mean ± se (standard error) of some of the physicochemical properties of soil used for experiments.
Irrigation water treatments.
Three weeks after transplanting, the BGW irrigation treatments began. There were five salinity treatments, three of them were tap water of EC 0.6 dS/m (control), BGW of EC 4.0 dS/m, and RO concentrate of 8.0 dS/m. The BGW and RO concentrate were provided by the Brackish Groundwater National Desalination Research Facility, Alamogordo, NM. The chemical analysis of irrigation water including Na+, K+, Mg2+, Ca2+, and Cl− ions were listed in Table 2. These three treatments were continued for the entire duration of the experiments from 3 weeks after transplanting to fruiting stages. Our previous experiments showed that continued irrigation with EC of 4.0 dS/m and 8.0 dS/m beyond the flowering stage caused flower death (Baath, 2016). Therefore, two other treatments were set up in which the irrigation waters of 4.0 dS/m and 8.0 dS/m were changed to irrigation waters of 2.0 dS/m and 6.0 dS/m (diluted from 4.0 dS/m and 8.0 dS/m, respectively) from the beginning of the flowering stage. Thus, there were five irrigation treatments of 0.6, 2.0, 4.0, 6.0, and 8.0 dS/m (Fig. 1) and each treatment had four replicates (pots).
Schematic illustration of experimental treatments.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Schematic illustration of experimental treatments.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Schematic illustration of experimental treatments.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Mean ± se (standard error) for ion compositions of brackish water and RO concentration and chemical properties of soil after harvesting.
Plant measurements.
After applying the treatments to the pots, the height of each plant from the soil surface to the top of the main stem was measured once a month. Days to flower initiation from the sowing date was recorded. Number of flowers, divided into dying and healthy, were recorded for each plant once a week. At fruiting stage, Pn and gS were recorded at midday using a portable photosynthesis system (Model LI- COR 6400, Lincoln, NE) on April 6, April 26, May 8, and May 19, 2018, respectively. At the end of the experiment, four plants of each treatments were harvested and stems, leaves, and fruits were separately collected. The plants were dried in an oven at 75°C to a constant weight (about three days), afterward, the total dry biomass was ground to determine the concentrations of sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and chloride (Cl). Soil samples were taken from each pot for chemical analysis.
Statistical analysis.
Conic pots for the experiment were arranged in a completely randomized design with two cultivars, five irrigation treatments, and four replicates. The data were analyzed using one-way ANOVA within each cultivar. Differences among the mean values were identified using Turkey’s range test at α ≤ 0.05. SPSS version 23.0 (IBM Statistics) was used for all statistical analyses.
Results
Flowering.
The number of flowers for both cultivars decreased with increasing irrigation water salinity. For treatments EC 4.0 and EC 8.0, the number of flowers significantly decreased by 83.3% and 63.8% in ‘NuMex Joe E. Parker’, respectively, and 74.3% and 47.0% in ‘NuMex Sandia Select’, respectively, in relationship to the control (Table 3). These results suggested that the flowering trait of ‘NuMex Joe E. Parker’ was more sensitive to salinity than that of the ‘NuMex Sandia Select’.
Number of flowers, number of drying flowers and number of fruits for two chile pepper cultivars under different salinity treatments.
The number of flowers in treatments EC 2.0 and EC 6.0 decreased by 41.6% and 48.2%, respectively, as compared with the control for ‘NuMex Joe E. Parker’. Consequently, the number of fruits for ‘NuMex Joe E. Parker’ under treatment EC 2.0 were five times more than that of EC 4.0 treatment. Similarly, the number of fruits in EC 6.0 were 43.5% more than that in EC 8.0 (Table 3).
For ‘NuMex Sandia Select’, a decrease of 19.7% and 41.5%, in number of flowers for the EC 2.0 and EC 6.0 treatments, respectively, was observed as compared with the control. The number of fruits decreased by 15.9% and 25.4% under treatments EC 2.0 and EC 6.0, and 73% and 63.5% under treatments EC 4.0 and EC 8.0, respectively, as compared with the control. These results suggest that decreasing EC of irrigation water from 4.0 to 2.0 and 8.0 to 6.0 dS/m, respectively, from the beginning of the flowering stage decreased the salinity-induced abiotic stress on plants resulting in less flower death.
Compared with the control, irrigation with EC of 4.0 and 8.0 dS/m water significantly increased the time to flowering and time to fruit setting for both NuMex Joe E. Parker and NuMex Sandia Select cultivars (Table 4). However, increases in days to flowering and days to fruiting under treatments EC 2.0 and EC 6.0 were not significantly different as compared with the control. For the cultivar NuMex Joe E. Parker, days to flowering increased 0% and 11.2% under treatments EC 2.0 and EC 4.0, respectively, and 5.6% and 39% under treatments EC 6.0 and EC 8.0, respectively. With ‘NuMex Sandia Select’, days to flowering increased 8.4% and 52.4% under treatments EC 2.0 and EC 4.0, treatments EC 6.0 and EC 8.0 increase the time 3.9% and 40.2%, respectively, as compared with the control. Similar trends were found in days to fruiting for both cultivars (Table 4).
Days to flowering and fruiting for two chile pepper cultivars under different salinity levels.
Plant height.
A significant salinity effect on plant height at 60 and 90 d after transplanting was observed when irrigated with 4.0 and 8.0 dS/m saline water in both ‘NuMex Joe E. Parker’ and ‘NuMex Sandia Select’ (Table 5). Increasing salinity significantly decreased the height of plants as compared with the control; however, the differences between EC 4.0 and EC 8.0 treatments were not significant. When irrigation water salinity reduced from 4.0 dS/m to 2.0 dS/m at the flowering stage, plant height at 30, 60, and 90 d after transplanting were significantly higher than that of continuous 4.0 dS/m water irrigated plants for both cultivars. While when irrigation water salinity was reduced from 8.0 dS/m to 6.0 dS/m, the significant difference appeared only at 90 d after transplanting for both cultivars. Generally, plant height was higher for ‘NuMex Joe E. Parker’ than ‘NuMex Sandia Select’ among all treatments.
Plant height for two chile pepper cultivars under different salinity treatments throughout the growth stages.
Fresh shoot weight and fruit yield.
‘NuMex Joe E. Parker’ produced greater fresh shoot weight than that of ‘NuMex Sandia Select’ under different salinity levels except for the control (Fig. 2A). For both cultivars, fresh shoot weight significantly decreased with increasing salinity levels at 4.0 and 8.0 dS/m. However, no significant differences were observed between control and 2.0 dS/m irrigated pots. The fruit yield per plant decreased with increasing salinity levels (Fig. 2B). Maximum fruit yield was observed for the control, while the minimum fruit yield was for 8.0 dS/m. No significant differences were observed between 0.6 and 2.0 dS/m treatments as well as between 4.0 and 6.0 dS/m treatments for both cultivars. ‘NuMex Joe E. Parker’ had higher fruit yield at 0.6 and 2.0 dS/m levels, but ‘NuMex Sandia Select’ produced higher yields at 4.0, 6.0, and 8.0 dS/m salinity levels.
Fresh shoot weight (A) and fruit yield (B) for two chile pepper cultivars under different salinity levels. Different letters for each cultivar correspond to Turkey’s range tests at 0.05 P level.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Fresh shoot weight (A) and fruit yield (B) for two chile pepper cultivars under different salinity levels. Different letters for each cultivar correspond to Turkey’s range tests at 0.05 P level.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Fresh shoot weight (A) and fruit yield (B) for two chile pepper cultivars under different salinity levels. Different letters for each cultivar correspond to Turkey’s range tests at 0.05 P level.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Leaf gas exchange.
Leaf Pn for both cultivars decreased at 4.0 and 8.0 dS/m in comparison with the control, but no significant differences were observed (Fig. 3A). When the irrigation water salinity was reduced from 4.0 and 8.0 dS/m to 2.0 and 6.0 dS/m, the Pn of ‘NuMex Joe E. Parker’ were 13.5 and 13.3 μmol·m−2·s−1, respectively, which were higher than 12.8 μmol·m−2·s−1 of the control, but the differences were not significant. gS significantly decreased at 4.0 and 8.0 dS/m salinity levels as compared with the control for both cultivars (Fig. 3B). However, no significant differences were seen for gS between control and 2.0 dS/m as well as in 6 and 8 dS/m.
Photosynthetic rate (A) and gS (B) for two chile pepper cultivars under different salinity levels. Different letters for each cultivar correspond to Turkey’s range tests at 0.05 P level.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Photosynthetic rate (A) and gS (B) for two chile pepper cultivars under different salinity levels. Different letters for each cultivar correspond to Turkey’s range tests at 0.05 P level.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Photosynthetic rate (A) and gS (B) for two chile pepper cultivars under different salinity levels. Different letters for each cultivar correspond to Turkey’s range tests at 0.05 P level.
Citation: HortScience 57, 9; 10.21273/HORTSCI16682-22
Ion concentrations.
The concentrations of Na+, Cl-, Mg2+, Ca2+, and K+ ions in soil and leachate water significantly increased with increasing irrigation water salinity except K+ concentration in soil (Table 2). The Mg2+ and Cl− concentrations in leaves significantly increased with increasing irrigation water salinity, while leaf Ca2+ concentrations were unchanged for both cultivars. There were significant increases in leaf Na+ concentrations for 4.0 and 8.0 dS/m levels as compared with the control for both cultivars, while significant decreases in leaf K+ concentration were noted at 8.0 dS/m level. Na+ and Cl− concentrations in leaves were lower for ‘NuMex Joe E. Parker’ than ‘NuMex Sandia Select’ within all the treatments (Table 6).
Ion concentrations in plant leaf, stem, and fruit for two chile pepper cultivars under different salinity levels.
For both cultivars, Ca2+ concentrations in stems significantly decreased, while Mg2+, Na+, and Cl− concentrations in stems increased with increasing irrigation water salinity. K+ concentration in stems significantly decreased only at 8.0 dS/m level. Moreover, Na+ and Cl− concentration in stems were lower in ‘NuMex Joe E. Parker’ than ‘NuMex Sandia Select’ under all the treatments except Cl− concentration under EC 4.0 treatment (Table 6).
No significant differences of K+, Mg2+, and Ca2+ concentrations in fruits were observed for either cultivars. Na+ and Cl− concentrations in fruits increased with increasing irrigation water salinity for both cultivars, but no significant differences were observed between 4.0 dS/m and 8.0 dS/m treatments.
Evapotranspiration and leached water.
ETa significantly decreased for treatments EC 4.0 and EC 8.0 as compared with the control for both cultivars (Table 7), while plant ETa under 2.0 dS/m and 6.0 dS/m treatments were significantly higher than those under 4.0 dS/m and 8.0 dS/m treatments, respectively. ‘NuMex Sandia Select’ had higher ETa than ‘NuMex Joe E. Parker’ at 0.6 dS/m (control), but showed a greater reduction under all the salinity treatments. Leached water increased with increasing irrigation with water salinity; however, significant differences were noted only at 8.0 dS/m level in comparison with control for both cultivars (Table 7). Reduced salinity of irrigation water from the flowering stage decreased leached water, though significant differences were only observed between 4.0 dS/m and 8.0 dS/m treatments.
Total ETa, total DP, and mean LF for two chile pepper cultivars under different salinity levels.
Discussion
With irrigation water salinity increasing from 4.0 dS/m to 8.0 dS/m, the flower numbers and fruit numbers for both chile pepper cultivars decreased, moreover, phonological traits like days to flowering and days to fruiting increased (Tables 3 and 4). Consistent with the results of Zhu (2001), our results indicated that irrigated water salinity prolonged the vegetative growth stage and delayed reproductive development. However, Baath et al. (2017) observed days to flowering decreased with increasing salinity levels in five selected chile pepper cultivars, indicating that both duration and period of plant exposure to salinity would affect the transition from vegetative growth to reproductive growth. To the best of our knowledge, quantitative information available on the effects of the application of saline water at different growth periods on chile flowering is meager. Flowering is a key link in the transition of plants from vegetative growth to reproductive growth (Song et al., 2013). Plants irrigated with reduced salinity waters (2.0 and 6.0 dS/m) from the flowering stage decreased days to flower and to set fruits but increased the number of flowers and the number of fruits significantly than those continuously irrigated with 4.0 and 8.0 dS/m salinity water throughout the growth stage for both cultivars (Tables 3 and 4). Salt stress disrupts plant nutrient uptake and moist content balance, which induces plant growth and flower development (Abbas et al., 2014). It was reported that salinity delayed the flowering of chili (Balasankar et al., 2017), tomato (Turhan et al., 2009), and Iris hexagona (Van Zandt and Mopper, 2002). Our results show that changing irrigation with reduced salinity water at the flowering stage accelerated the flowering stage and alleviated the adverse influence of salinity on the number of flowers and the number of fruits of chile pepper.
Irrigation with RO and BGW increased Mg2+, Cl−, and Na+ concentration in soil by 2–20 times as compared with the control (Table 2). Ozturk et al. (2018) also reported that increasing water salinity levels increased ion content in the soil. Continuous irrigation with BGW of 4.0 dS/m and RO concentrate of 8.0 dS/m caused soil salinization due to salt accumulation. The Mg2+, Cl−, and Na+ concentrations in plant leaf, stem, and fruit increased with increasing water salinity levels (Table 6), which were consistent with ion accumulations in soil. While K+ concentration in leaf and stem showed a significant decrease under EC 8.0 treatment, Ca2+ concentration also decreased under treatment EC 8.0 compared with control. Del Amor et al. (2001) also reported that Ca2+ and K+ concentrations in plant leaf and fruit decreased significantly with increasing salinity of nutrient solutions. Generally, plants absorb more Na+ and less K+ regardless of genotype in soils with high sodium content (Ruiz-Lozano et al., 2012; Moles et al., 2016).
Plant height decreased for both cultivars with increasing salinity levels as has been seen in other research (Chartzoulakis and Klapaki, 2000; Miyamoto et al., 1985; Yildirim and Güvenç, 2006). We determined that 30 d after transplanting plant heights were similar for all treatments. However, 60 d after transplanting, plant heights decreased with increasing irrigation water salinity. These results substantiated that chile pepper can tolerate irrigation with salty water for a short period. However, plant growth is hinder due to osmotic stress of external salts when irrigation is continued for a long period (Munns et al., 1995). Alleviating osmotic effects by decreasing irrigation water salinity from 4.0 to 2.0 dS/m and from 8.0 to 6.0 dS/m at the flowering stage increased plant heights.
Decreases in photosynthetic rate under salinity treatments were observed in this study and others (Delfine et al., 1999; Rasmuson and Anderson, 2002; Singh et al., 2014). This could be due to the limitation of CO2 into the stomata, which inhibits photosynthesis under salinity stress (Delfine et al., 1999). Both photosynthetic and gS rates increased when substituting 4.0 and 8.0 dS/m to 2.0 and 6.0 dS/m, respectively, from the flowering stage for the two cultivars.
Akhtar et al. (2017) reported that increasing salinity stress decreased plant biomass and fruit yield of chile pepper. Our results showed that irrigation with 4.0 and 8.0 dS/m water significantly decreased ETa, fresh shoot weight, and fruit yield as compared with control (Fig. 2), which was also consistent with results reported by Flores et al. (2016). Changing irrigation with water of 2.0 dS/m salinity increased ETa for ‘NuMex Joe E. Parker’ and ‘NuMex Sandia Select’ by 22.8% and 35.0%, respectively, as compared with the 4.0 dS/m level. Similarly, changing water of 8.0 dS/m to 6.0 dS/m increased ETa by 26.5% and 27.8%, respectively, for the two cultivars (Table 7). Decreasing EC of irrigation water from the beginning of the flowering stage mitigated the salinity-induced abiotic stress on plant growth, consequently resulting in higher pod yield. LFs in this study ranged between 15% and 40% to maintain soil salinity (Beltrán, 1999). Salinity tolerance is based on complex genetic systems and successful genetic enhancement programs need to have sources of tolerance to incorporate into plant breeding programs. These results indicated that there is genetic diversity for salt tolerance within chile peppers that can be manipulated to increase tolerance. This information will be beneficial to plant breeders, as genetic variability within chile pepper germplasm can be incorporated into future cultivar releases to improve the salinity tolerance of chile peppers.
Conclusion
This study evaluated the flowering, growth, yield, and ion uptake of two chile pepper cultivars irrigated with natural brackish well water and RO concentrate at different growth stages. Irrigation with increasing water salinity decreased flower numbers and fruit numbers, stunted plant growth, delayed flowering, fruit setting time, reduced photosynthesis, and gS, consequently accompanied by reductions in fresh shoot and fruit weight. Importantly, irrigation with waters of reduced salinity at the flowering stage initiated reproductive development more rapidly and alleviated the adverse influence of salinity on the number of flowers, plant height, plant water uptake and photosynthesis, and biomass of chile peppers consequently resulting in higher fruit yield. This research established a novel irrigation scheduling protocol for sustaining chile pepper production while irrigating with saline water.
Literature Cited
Abbas, F., Al-Jbawi, E. & Ibrahim, M. 2014 Growth and chlorophyll fluorescence under salinity stress in sugar beet (Beta vulgaris L.) Int. J. Environ. 3 1 1 9 https://doi.org/10.3126/ije.v3i1.9937
Akhtar, M.F., Hussain, A., Ahmad, F., Kharal, M.A., Khalid, I., Latif, M. & Jamshaid, M.U. 2017 Screening of pepper (Capsicum annuum L.) genotypes against salinity stress J. Environ. Agr. Sci. 11 51 58
Aktas, H., Abak, K. & Cakmak, I. 2006 Genotypic variation in the response of pepper to salinity Scientia Horticulturae 110 3 260 266 https://doi.org/10.1016/j.scienta.2006.07.017
Alvarez, S., Gomez-Bellot, M.J., Castillo, M., Banon, S. & Sanchez-Blanco, M.J. 2012 Osmotic and saline effect on growth, water relations: And ion uptake and translocation in Phlomis purpurea plants Environ. Exp. Bot. 78 138 145 https://doi.org/10.1016/j.envexpbot.2011.12.035
Ashraf, M.Y. & Wu, L. 1994 Breeding for salinity tolerance in plants Crit. Rev. Plant Sci. 13 17 42 https://doi.org/10.1080/07352689409701906
Ashraf, M. & Foolad, M. 2007 Roles of glycine betaine and proline in improving plant abiotic stress resistance Environ. Exp. Bot. 59 206 216 https://doi.org/10.1016/j.envexpbot.2005.12.006
Ayers, R.S. & Wescot, D.W. 1985 Water quality for agriculture FAO, Rome. http://www.fao.org/docrep/003/T0234E/T0234E02.htm
Baath, G.S. 2016 Irrigating chile pepper (Capsicum annuum) with brackish groundwater and reverse osmosis concentrate: Balancing sustainability, quality, and water scarcity (Doctoral dissertation, New Mexico State University)
Baath, G.S., Shukla, M.K., Bosland, P.W., Steiner, R.L. & Walker, S.J. 2017 Irrigation water salinity influences at various growth stages of Capsicum annuum Agr. Water Manage. 179 246 253 https://doi.org/10.1016/j.agwat.201 6.05.028
Baath, G.S., Shukla, M.K., Bosland, P.W., Walker, S.J., Saini, R.K. & Shah, R. 2020 Water use and yield responses of chile pepper cultivars irrigated with brackish groundwater and reverse osmosis concentrate Horticulturae 6 2 27 39 https://doi.org/10.3390/horticulturae6020027
Balasankar, D., Praneetha, S., Armugam, T., Manivannan, N., Jeyakumar, P. & Arulmozhiselvan, K. 2017 Assessment of salinity tolerance in chilli (Capsicum annum L.) genotypes Int. J. Chem. Stud. 5 6 1194 1198
Beltrán, J.M 1999 Irrigation with saline water: Benefits and environmental impact Agr. Water Manage. 40 183 194 https://doi.org/10.1016/S0378-3774(98)00120-6
Blake, G.R. & Hartge, K.H. 1986 Bulk density 363 376 Klute, A. Methods of soil analysis. Part 1 2nd ed. ASA and SSSA, Agronomy Monographs Madison, WI
Bosland, P.W. & Walker, S. 2014 Growing Chiles in New Mexico Cooperative Extension Service, College of Agriculture, Consumer and Environmental Sciences, New Mexico State University. https://pubs.nmsu.edu/_h/H230/
Chartzoulakis, K. & Klapaki, G. 2000 Response of two greenhouse pepper hybrids to NaCl salinity during different growth stages Scientia Hort. 86 247 260 https://doi.org/10.1016/S0304-4238(00)00151-5
Del Amor, F.M., Martinez, V. & Cerdá, A. 2001 Salt tolerance of tomato plants as affected by stage of plant development HortScience 36 1260 1263 https://doi.org/10.21273/HORTSCI.36.7.1260
Delfine, S., Alvino, A., Villani, M.C. & Loreto, F. 1999 Restrictions to carbon dioxide conductance and photosynthesis in spinach leaves recovering from salt stress Plant Physiol. 119 1101 1106 https://doi.org/10.1104/pp.119.3.1101
Díaz, F.J., Benes, S.E. & Grattan, S.R. 2013 Field performance of halophytic species under irrigation with saline drainage water in the San Joaquin Valley of California Agr. Water Man. 118 59 69 https://doi.org/10.1016/j.agwat.2012.11.017
Duan, R. & Fedler, C.B. 2013 Salt management for sustainable degraded water land application under changing climatic conditions Environ. Sci. Technol. 47 10113 10114 https://doi.org/10.1021/es403619m
Flores, A.M., Schutte, B.J., Shukla, M.K., Picchioni, G.A. & Ulery, A.L. 2015 Time-integrated measurements of seed germination for salt-tolerant plant species Seed Sci. Technol. 43 1 7 https://doi.org/10.15258/sst.2015.43.3.09
Flores, A.M., Shukla, M.K., Daniel, D., Ulery, A.L., Schutte, B.J., Picchioni, G.A. & Fernald, S. 2016 Evapotranspiration changes with irrigation using saline groundwater and RO concentrate J. Arid Environ. 131 35 45 https://doi.org/10. 1016/j.jaridenv.2016.04.003
Flores, A., Shukla, M.K., Schutte, B., Picchioni, G. & Daniel, D. 2017 Physiologic response of six plant species grown in two contrasting soils and irrigated with brackish groundwater and RO concentrate Arid Land Res. Manage. J. 31 182 203 https://doi.org/10.1080/15324982.2016.1275068
Farooq, M., Hussin, M., Wakeel, A. & Siddique, K.H.M. 2015 Salt stress in maize: Effects, resistance mechanisms, and management. A review Agron. Sustain. Dev. 35 461 481 https://doi.org/10.1007/s13593-015-0287-0
Gee, G.W. & Bauder, J.W. 1986 Particle size analysis 337 382 Klute, A. Methods of soil analysis Part 1 2nd ed. ASA, Agronomy Monogram 9 Madison, WI
Ge, Z.M., Zhang, L.Q., Yuan, L. & Zhang, C. 2014 Effects of salinity on temperature-dependent photosynthetic parameters of a native C3 and a non-native C4 marsh grass in the Yangtze Estuary, China Photosynthetica 52 484 492 https://doi.org/10.1007/s11099-014-0055-4
Goldberg, N.P 2004 Chile pepper disorders caused by environmental stress Cooperative Extension Service, College of Agriculture, Consumer and Environmental Sciences, New Mexico State University. https://pubs.nmsu.edu/_h/H249/
Katerji, N., Van Hoorn, J.W., Hamdy, A., Karam, F. & Mastrorilli, M. 1994 Effect of salinity on emergence and on water stress and early seedling growth of sunflower and maize Agr. Water Manage. 26 1 81 91 https://doi.org/10.1016/0378-3774(94)90026-4
Koyro, H.W., Hussain, T., Huchzermeyer, M.B. & Khan, A. 2013 Photosynthetic and growth responses of a perennial halophytic grass Panicum turgidum to increasing NaCl concentrations Environ. Exp. Bot. 91 22 29 https://doi.org/10.1016/j.envexpbot.2013.02.007
Lansford, R., Hernandez, J., Enis, P., Truby, D. & Mapel, C. 1990 Evaluation of available saline water resources in New Mexico for the production of microalgae Solar Energy Research Institute Golden, CO
Läuchli, A. & Epstein, E. 1990 Plant responses to saline and sodic conditions Agr. Salin. Assess. Manage. 71 113 137 10.1061/9780784411698.ch06
Maas, E.V. & Hoffman, G.J. 1977 Crop salt tolerance–current assessment J. Irrig. Drain. Div. 103 2 115 134 https://doi.org/10.1061/JRCEA4.0001137
Miyamoto, S., Piela, K. & Petticrew, J. 1985 Salt effects on germination and seedling emergence of several vegetable crops and guayule Irrig. Sci. 6 3 159 170 https://doi.org/10.1007/BF00572664
Miyamoto, S., Glenn, E.P. & Singh, N.T. 1994 Utilization of halophytic plants for fodder production with brackish water in subtropic deserts 43 76 Squires, V.R. & Ayoub, A.T. Halophytes as a resource for livestock and for rehabilitation of degraded lands. Kluwer Academic Publishers Dordrecht
Moles, T.M., Pompeiano, A., Reyes, T.H., Scartazza, A. & Guglielminetti, L. 2016 The efficient physiological strategy of a tomato landrace in response to short-term salinity stress Plant Physiol. Biochem. 109 262 272 https://doi.org/10.1016/j.plaphy.2016.10.008
Munns, R., Schachtman, D.P. & Condon, A.G. 1995 The significance of a two-phase growth response to salinity in wheat and barley Funct. Plant Biol. 22 4 561 569 https://doi.org/10.1071/PP9950561
Munns, R. & Tester, M. 2008 Mechanisms of salinity tolerance Annu. Rev. Plant Biol. 59 651 681 https://doi.org/10.1146/annurev.arplant.59.032607.092911
Niu, G., Rodriguez, D.S., Cabrera, R., Jifon, J., Leskovar, D. & Crosby, K. 2010a Salinity and soil type effects on emergence and growth of pepper seedlings HortScience 45 1265 1269 https://doi.org/10.21273/HORTSCI.45.8.1265
Niu, G., Rodriguez, D.S., Crosby, K., Leskovar, D. & Jifon, J. 2010b Rapid screening for relative salt tolerance among chile pepper genotypes HortScience 45 8 1192 1195 https://doi.org/10.21273/HORTSCI.45.8.1192
Noaman, M.N. & El-Haddad, E.S. 2000 Effects of irrigation water salinity and leaching fraction on the growth of six halophyte species J. Agr. Sci. 135 279 285 https://doi.org/10.1017/S0021859699008333
Ozturk, O.F., Shukla, M.K., Stringam, B., Picchioni, G.A. & Gard, C. 2018 Irrigation with brackish water changes evapotranspiration, growth and ion uptake of halophytes Agr. Water Manage. 195 142 153 https://doi.org/10.1016/j.agwat.2017.10.012
Pasternak, D.M., Twersky, M. & de Malach, Y. 1979 Salt resistance in agricultural crops 127 142 Mussell, H. & Staples, R.C. Stress physiology in crop plants. Wiley New York, NY
Pasternak, D. & Malach, Y.D. 1994 Crop irrigation with saline water 599 622 Pessarakli, M. Handbook of plant and crop stress. Marcel Dekker New York, NY
Rasmuson, K.E. & Anderson, J.E. 2002 Salinity affects development, growth, and photosynthesis in cheat grass J. Range Manage. 55 80 87 https://doi.org/10.2307/4003267
Ruiz-Lozano, J.M., Porcel, R., Azcón, C. & Aroca, R. 2012 Regulation by arbuscular mycorrhizae of the integrated physiological response to salinity in plants: New challenges in physiological and molecular studies J. Expt. Bot. 63 11 4033 4044 https://doi.org/10.1093/jxb/ers126
Shannon, M., Cervinka, V. & Daniel, D. 1997 Drainage water reuse Madramootoo, C., Johnson, W. & Willardson, L. Management of agricultural drainage water quality FAO Rome http://www.fao.org/docrep/w7224e/w7224e08.htm
Shannon, M.C. & Grieve, C.M. 1998 Tolerance of vegetable crops to salinity Scientia Hort. 78 1 5 38 https://doi.org/10.1016/S0304-4238(98)00189-7
Shukla, M.K 2014 Soil physics: An introduction CRC Press Boca Raton, FL 58
Singh, S., Grover, K., Begna, S., Angadi, S., Shukla, M.K., Steiner, R. & Auld, D. 2014 Physiological response of diverse origin spring safflower genotypes to salinity Sabaku Kenkyu 24 169 174
Smedema, L.K. & Shiati, K. 2002 Irrigation and salinity: A perspective review of the salinity hazards of irrigation development in the arid zone Irrig. Drain. Syst. 16 161 174 https://doi.org/10.1023/A:1016008417327
Song, Y.H., Ito, S. & Imaizumi, T. 2013 Flowering time regulation: Photoperiod- and temperature-sensing in leaves Trends Plant Sci. 18 10 575 583 https://doi.org/10.1016/j.tplants.2013.05.003
Turhan, A., Seniz, V. & Kusçu, H. 2009 Genotypic variation in the response of tomato to salinity Afr. J. Biotechnol. 8 6 1062 1068 https://doi.org/10.4314/AJB.V8I6.60015
UNEP International Environmental Technology Center 1998 Desalination by reverse osmosis Sourcebook of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean. https://www.oas.org/dsd/publications/Unit/oea59e/begin.htm#Contents
U.S. Department of Agriculture National Agricultural Statistics Service 2021 https://www.nass.usda.gov/Statistics_by_State/New_Mexico/Publications/Special_Interest_Reports/NM
Van Zandt, P.A. & Mopper, S. 2002 Delayed and carryover effects of salinity on flowering in Iris hexagona (Iridaceae) Amer. J. Bot. 89 11 1847 1851 https://doi.org/10.3732/ajb.89.11.1847
Yildirim, E. & Güvenç, İ. 2006 Salt tolerance of pepper cultivars during germination and seedling growth Turk. J. Agr. For. 30 5 347 353
Zhu, J.K 2001 Plant salt tolerance Trends Plant Sci. 6 2 66 71 https://doi.org/10.1016/S1360-1385(00)01838-0
