Effect of saline irrigation water on yield and bio-chemical parameters of leafy vegetables

Introduction

Coriander (Coriandrum sativum) also called cilantro or Chinese parsley, feathery annual plant of the parsley family (Apiaceae), parts of which are used as both as herb and as spice. Spinach (Spinacia oleracea) is a leafy green flowering plant native to central and western Asia. It is of the family Amaranthaceae. Its leaves are a common edible vegetable consumed either fresh, or after storage using preservation techniques. Fenugreek (Trigonellafoenum graecum) is an annual plant belongs to the family Leguminoceae. It is the famous spices in human food. The seeds and green leaves of fenugreek are used in food as well as in medicinal application that is the old practice of human history. In Saurashtra, region of Gujarat, the main source of irrigation is well/tubewell water and majority of these waters are either saline or sodic or both. However, the farmers of this region grow these leafy vegetables with this poor quality water to meet their requirement under such condition, the soil properties and crop yield are adversely affected, hence, cultivation of this crops are not economical. However, by selecting suitable leafy vegetables, it could be possible to harvest better crop yield.

Materials and Methods

The experimental soil was clayey in texture and alkaline in reaction with pH 8.14, EC 0.58 dS/m, ESP 5.24 (%) and SAR 3.30 (me/l). The experiment consists of 12 treatments combinations comprising four levels of salinity water viz. < 2, 4, 6 and 8 dS/m and three different leafy vegetables viz. C 1 -Coriander (Variety GDLC-1), C 2 -Fenugreek (Variety PEB) and C 3 -Spinach-(Variety Local). Complete Randomized Design (Factorial) was used and treatments were repeated three time. Standard agronomic practices were adopted for raising healthy crop. In this study yield (g/plot), coriander equivalent yield (g/plot), germination%, plant height, plant Na/K ratio, chlorophyll content (µmol/m 2 ) and proline (µmol/g) content were recorded. Proline content was determined by determination of free proline method developed by Bates et al. (1973) [4] and method was employed for the extraction of chlorophyll from leaf tissue without maceration (DMSO) given by Hiscox and Israelstam, (1979) [10] .

Results and Discussion

Effect of different levels of saline irrigation water on yield and yield attributes

The data presented in Table-1 revealed that the application of irrigation water having EC < 2 dS/m gave significantly higher coriander equivalent yield (795 g/plot) in 2022-23, (940 g/plot), 2023-24 as well as in pooled results (867 g/plot). Significantly higher germination% (87.93), plant height (20.71cm) and chlorophyll content (57.05 µmol/m 2 ) were also reported with application of saline irrigation water having EC< 2 dS/m. While, significantly higher plant Na/K ratio (2.39) and proline content (0.173 µmol/g) were recorded with the application of irrigation water having EC-8 dS/m. Among the parameters under study, yield, coriander equivalent yield, germination%, plant height and chlorophyll content decreased and Na/K ratio and proline content increased with increase in salinity levels of irrigation water from 2 to 8 dS/m. Among the different leafy vegetable crops, spinach crop yielded significantly higher coriander equivalent yield (658, 719 and 689 g/plot) in 2022-23, 2023-24 as well as in pooled results, respectively. Significantly highest germination percentage (92.25%), plant height (28.09 cm) and proline content (0.182 µmol/g) were observed with spinach. Lowest Na/K ratio (1.22) was observed with coriander and highest chlorophyll content (57.71 µmol/m2) was observed with fenugreek (Table -2). Seed germination decrease with salinity stress; in fact, high salinity inhibits it by causing osmotic stress (preventing water uptake) and ionic toxicity (damaging enzymes and cellular components). Proline content increases during salinity stress in plants because it functions as an osmoprotectant, helping to maintain cell turgor and osmotic balance. It also acts as a cellular shield, stabilizing membranes and enzymes, scavenging free radicals, and providing a nontoxic nitrogen store. This multifaceted role helps the plant to survive and function under the damaging conditions of high salt concentrations. Our findings also corroborated with the finding of Aymen & Cherif (2013) [3] and Poonam (2024) [15] demonstrating that saline stress reduced plant growth of coriander. According to Mergeb, et al. (2020) [12] the salinity reduced germination uniformity and germination synchrony in fenugreek plant. The growth and yield parameters (number of leaves, and fresh and dry weight) of spinach genotypes were significantly decreased with increasing the EC levels of saline water (Bhatti, et. al., 2021) [5] . Salinity stress decreased shoot growth of fenugreek plants associated with leaf area and leaf number reduction (Hayet, 2019) [9] . Alaa El-Din et al. (2013) [1] reported that sodium chloride (NaCl) reduced seeds germination, plant length, number of leaves, plant strength, roots number and root length of coriander, while increasing the content of total soluble solids and proline.

Effect of salinity on soil parameter after harvest

The data given in Table-3 revealed that the significantly higher EC (1.61 dS/m), ESP (7.13%) and SAR (5.97) recorded with the application of saline irrigation water EC-8 dS/m. While, the lower value of EC (0.50 dS/m), ESP (5.08%) and SAR (3.20) recorded with the application of saline irrigation water having EC<2 dS/m. Effect of different crops on soil parameters under study were found non significant.

Interaction effect crop and salinity

Interaction effect of salinity and different crops was found significant with respect to yield, coriander equivalent yield, germination%, Na/K ratio in plant, chlorophyll content and prolien content in leaves. Significantly the highest yield (2017 g/plot), coriander equivalent yield (896 g/plot), germination% (94.00) and lowest Na/K ratio (0.69) were observed with treatment combination saline irrigation water 2 dS/m and spinach crop (Table 4 &5) and significantly higher chlorophyll content (73.00 µmol/m 2 ) was recorded with irrigation water having EC<2 dS/m and fenugreek crop. While, significantly the highest proline content (0.287 µmol/g) was observed when spinach crop irrigated with saline irrigation water having EC 8 dS/m (Table 6). In a study, Keshavarzi et al. (2011) [11] found spinach plants sensitive to salinity and advised that the crop should not be cultivated in saline soils. In contrast, recent studies report no significant loss in spinach yield and nutritional value with saline water levels up to 9 dS/m (Ors and Suarez, 2016 and Ferreira et al., 2018) [13,8] . In another study, spinach yield was increased at EC levels of 4 and 7 dS/m and subsequently declined at EC 9.0 dS/m and above (Ors and Suarez, 2017) [14] . Similarly, Ferreira et al. (2020) [7] suggested the threshold level for spinach between 7 to 10 dS/m for water salinity, and from 5.6 to 8.9 dS/m for soil salinity

Salt tolerance criteria of different leafy vegetables

The data presented in Table-7 indicated that the highest mean seed yield (619.64 g/plot) was recorded with spinach crop followed by fenugreek (414.88 g/plot) and the lowest with coriander crop (248.00 g/plot). The mean salinity index (69.12%) was found the highest in spinach crop followed by fenugreek (48.31%). Reduction in yield at EC 8.0 (dS/m) over control was observed the lowest in spinach (52.87%) followed by fenugreek (64.21%) and the highest with coriander (79.26%). The spinach crop was found higher salt tolerant for 50% yield decline (at EC level of irrigation water 8.02 dS/m) as compared to other crops.

Conclusion

From the forgoing results, it can be concluded that Among the different leafy vegetable crops like coriander, fenugreek and spinach, higher mean salinity index (69.12) and mean seed yield (619.64 g/plot), minimum yield decline (52.87%) at EC 8.0 dS/m and for 50% yield reduction at EC 8.02 dS/m, as well as lower Na/K ratio in seed and stalk were observed with spinach. Spinach crop found more salt tolerance as compared to coriander and fenugreek on the basis of salinity indices.

References

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