The Effect of Foliar Application of Sodium Selenite and Calcium Nitrate on Nitrate Accumulation in Spinach (Spinacia oleracea L.) in Shahrekord Region

Document Type : Research Article

Authors

A. Farahmandi ¹

B. Haghighati ²

B. Madani ³

¹ Department of Horticulture, Faculty of Agriculture, University of Bou Ali Sina, Hamedan, Iran

² Soil and Water Research Department, Chaharmahal and Bakhtiari Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Shahrekord, Iran

³ Horticulture Crops Research Department, Natural Resources Research and Education Center of Chaharmahal and Bakhtiari, AREEO, Shahrekord, Iran

https://doi.org/10.22067/jhs.2025.91050.1397

Abstract

Introduction
High nitrate concentration in vegetables is a major threat to human health. Selenium is an essential element for human health due to its effect on plant growth and development and its presence in antioxidant systems. The consumption of vegetables has been emphasized by nutritionists and is increasing due to their high nutritional value, as well as the provision of fiber and antioxidant compounds. For this reason, many vegetables, especially fresh vegetables, are considered to be essential as daily food for human. To solve the problem of nitrate accumulation in crops, it is recommended to provide solutions such as: selenium element feeding or using ammonia-based fertilizers. Selenium is essential as a cofactor for the formation of essential enzymes glutathione peroxidases, which are present in all living tissues. This enzyme reduces cellular peroxides and prevents harmful oxidation in the cell. Reactive oxygen species such as hydroperoxides and hydrogen peroxide are also deactivated by these enzymes. On the other hand, calcium nitrate is one of the important fertilizers in agriculture, which helps to improve the growth and quality of products, especially vegetables, due to its nitrogen and calcium content. The use of calcium nitrate can help reduce problems such as fruit rot and increase plant resistance to diseases and various types of stresses.
 
Materials and Methods
This research was conducted at the Chaharmahal and Bakhtiari Agricultural and Natural Resources Research Center, Shahrekord, in 2022-2023. The experiment was conducted in a completely randomized block design with 7 treatments in three replications. The treatments included sodium selenite at three levels (5.0, 1.0, and 1.5 mM) and calcium nitrate at three levels (5, 10, and 20 mM) and the control treatment. Each experimental unit contained 3 plants. After foliar spraying and applying treatments with sodium selenite and calcium nitrate, plant samples were collected and transferred to the laboratory. After two months of spinach growth (early July), various plant growth parameters were evaluated, including fresh and dry weight of roots and shoots, leaf area, plant height, and number of leaves. Several biochemical traits were also measured, such as chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, antioxidant capacity, total phenolic content, total flavonoid content, nitrate content, nitrate reductase activity, and selenium concentration in the leaves. Data were analyzed using analysis of variance (ANOVA) in the Statistical Analysis System (SAS) version 9.4 (SAS Institute Inc., Cary, NC, USA). Mean comparisons were performed using Duncan’s multiple range test at a significance level of p ≤ 0.05.
 
Results and Discussion
Based on the results, foliar application of sodium selenite and calcium nitrate had a significant effect on the amount of chlorophylls a, b, total and carotenoids. The results showed an increase in the amount of chlorophyll a, b and total and total carotenoid with increasing the amount of calcium nitrate. Also, the highest levels of chlorophylls a, b and total and total carotenoids were obtained for the treatments of sodium selenium 1 and 1.5 mM. Moreover, the lowest amount of chlorophylls a, b and total and total carotenoids were obtained for the control and 0.5 mM. The highest amount of total phenols, antioxidant activities were observed in the treatment of 20 mM calcium nitrate and 1.5 mM sodium selenite. Also, the highest content of nitrate reductase enzyme activity was obtained in the treatment of 20 mM calcium nitrate and 1.5 mM sodium selenite. The highest amount of nitrate was obtained in the control treatment and the highest amount of selenium was obtained for the treatment of 1.5 mM sodium selenite.
 
Conclusion
In this study, the effect of foliar application of sodium selenium and calcium nitrate on nitrate accumulation in spinach was investigated. In general, the results of this research showed that although selenium is not an essential element for plants, it can be used in different concentrations, especially in a concentration of 1.5 mM with the concentration of calcium nitrate by 20 mM to increase chlorophyll pigments in leaves. According to the results, foliar application of sodium selenite had a reducing effect on nitrate accumulation and an increasing effect on nitrate reductase enzyme activity and selenium accumulation inside the spinach plant. Therefore, foliar application of 1.5 mM sodium selenite is recommended for the production of spinach with the maximum amount of antioxidant compounds, selenium and the minimum amount of nitrate accumulation which can be effective in increasing the growth of the plant, and as a result, increasing amount of photosynthesis and carbon fixation, which ultimately leads to increasing the growth rate of spinach.

Keywords

Antioxidant activity

Biochemical

Carotenoid

Nitrate reductase enzyme

Treatment

Subjects

• Growing vegetables

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Authors retain the copyright. This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0).

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