Determination of the Critical Saturated Water Accumulation Curve for Spinach (Spinacia oleracea L.) under Greenhouse Conditions

Document Type : Research Paper

Authors

1 Department of Horticultural Sciences, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.

2 Department of Horticultural Science, Faculty of Agriculture, College of Agriculture& Natural Resources, University of Tehran, Karaj, Iran.

3 Department of Irrigation and Reclamation Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.

Abstract

Considering the global water crisis and agriculture's crucial role in water use, optimizing irrigation in controlled environments, such as greenhouses, is becoming increasingly important. Spinach (Spinacia oleracea L.) a leafy vegetable is sensitive to water deficit and requires precise irrigation management for optimal yield. This study specifically aims to determine the Critical Saturated Water Accumulation (CSWA) curve and the Water Deficit Index (WDI) for spinach throughout its growth period under greenhouse conditions, guiding irrigation strategies. This experiment was conducted in the research greenhouse of the University of Tehran during two cropping cycles in 2023, using a completely randomized design with seven irrigation treatments and three replications. Based on dry matter weight data, the CSWA curve was derived as CSWA = 11.74 DM⁰·⁹¹. The developed model was subsequently validated using data from the second cropping cycle. The statistical indicators R², RRMSE, MBE, and d were 0.97, 8.16, 0.06, and 0.99, respectively, confirming the high accuracy of the model. The WDI values ranged from 0.71 to 1.13 in the first cropping cycle and from 0.65 to 1.19 in the second cycle. The WDI reliably reflected variations in plant water status among different irrigation treatments, as indicated by its strong correlation with dry biomass yield (R² = 0.97). These findings suggest that the CSWA and WDI models can be effectively applied to schedule irrigation with precision in greenhouse spinach production, laying the groundwork for intelligent irrigation system development.

Keywords

Main Subjects

Introduction

Given the global water crisis and the substantial share of agriculture in water consumption, optimizing irrigation in controlled environments such as greenhouses has become increasingly critical. Spinach (Spinacia oleracea L.), as a drought-sensitive leafy vegetable, requires precise water management throughout its growth cycle. This study aims to enhance irrigation efficiency by determining the Critical Saturated Water Accumulation curve (CSWA) and validating the Water Deficit Index (WDI) for greenhouse-grown spinach, thereby enabling accurate scheduling and the development of intelligent irrigation systems.

Objective(s)

This study was conducted to determine the Critical Saturated Water Accumulation curve (CSWA) and the Water Deficit Index (WDI) throughout the growth period of spinach under greenhouse conditions and various irrigation treatments.

Material and Methods

The experiment was conducted in the research greenhouse of the College of Agriculture and Natural Resources, University of Tehran, located in Karaj. During the cultivation period, the average greenhouse temperature was maintained at 23 °C, while the mean relative humidity was recorded at 48%. Furthermore, the average light intensity measured throughout the cultivation period was 100 μmol·m⁻²·s⁻¹. To regulate the ambient temperature, the greenhouse was equipped with a fan system and central heating. A completely randomized design was employed, consisting of seven irrigation treatments and three replications. The treatments corresponded to irrigation levels of 40%, 60%, 80%, 100%, 120%, 140%, and 160% of field capacity, respectively. The study was conducted over two successive cultivation periods using baby spinach (Spinacia oleracea L., cv. Racoon). During the first cultivation cycle, data were collected to establish the Critical Saturated Water Accumulation curve (CSWA). In the second cycle, the accuracy of the proposed methods was evaluated using statistical indicators including the coefficient of determination (R²), mean bias error (MBE), relative RMSE (RRMSE), and Willmott’s index of agreement (d). The Water Deficit Index (WDI) was calculated by dividing the actual Saturated Water Accumulation (SWA) of the plant by its Critical SWA, based on the corresponding dry matter content.

Results

Irrigation treatments had a significant effect on the dry biomass production of spinach. Increasing irrigation levels up to 100% of field capacity led to higher dry matter accumulation, while no statistically significant differences were observed at higher levels (120–160% of field capacity). The relationship between dry matter and critical saturated water accumulation (CSWA) was modeled with high accuracy using a power function: CSWA = 11.736 × DM⁰·⁹¹⁴, with a coefficient of determination of R² = 0.99. This curve indicated that as dry matter increased, the critical water accumulation also rose. Dry matter and saturated water accumulation data from the second cultivation were used to validate the CSWA model. The high R² value and RRMSE below 10% confirmed the model’s precision and reliability. The Water Deficit Index (WDI) ranged from 0.71 to 1.13 in the first cultivation and from 0.65 to 1.19 in the second. This index effectively reflected the plant’s water status and showed a significant correlation with dry biomass yield.

Conclusions

The results of this study demonstrated that the Critical Saturated Water Accumulation curve (CSWA) and the Water Deficit Index (WDI) are effective tools for assessing the water status of spinach under greenhouse conditions. The strong correlation between dry biomass and critical water accumulation indicates that improved water availability enhances photosynthesis, nutrient uptake, and ultimately biomass production. Model validation during the second cultivation confirmed the high accuracy of the derived CSWA equation. Moreover, the WDI index successfully distinguished water status across different irrigation treatments and showed a significant association with dry matter yield. Therefore, the application of these indices offers a precise and practical approach for irrigation planning and water resource management in greenhouse spinach cultivation.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authorship contribution

All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.

Declaration of Generative AI and AI-assisted technologies in the writing process

During the preparation of this work the authors used the artificial intelligence tool ChatGPT in order to review and check the grammar.

Data availability statement

Data available on request from the authors.

 

Acknowledgements

The authors would like to thank Horticultural Science Department of University of Tehran for providing equipments and Facilities in the present study.

Ethical considerations

The authors avoided data fabrication, falsification, and plagiarism, and any form of misconduct.

Conflict of interest

The authors declare no conflict of interest.

References

Abbas, K., Li, J., Gong, B., Lu, Y., Wu, X., Lü, G., & Gao, H. (2023). Drought stress tolerance in vegetables: the functional role of structural features, key gene pathways, and exogenous hormones. International Journal of Molecular Sciences, 24(18), 13876.
Ahmed, Z., Gui, D., Murtaza, G., Yunfei, L., & Ali, S. (2023). An overview of smart irrigation management for improving water productivity under climate change in drylands. Agronomy, 13(8), 2113.
Adom, R. K., Simatele, M. D., & Reid, M. (2022). Addressing the challenges of water-energy-food nexus programme in the context of sustainable development and climate change in South Africa. Journal of Water and Climate Change, 13(7), 2761-2779.
Anjos Neto, A. P. D., Oliveira, G. R. F., Mello, S. D. C., Silva, M. S. D., Gomes-Junior, F. G., Novembre, A. D. D. L. C., & Azevedo, R. A. (2020). Seed priming with seaweed extract mitigate heat stress in spinach: effect on germination, seedling growth and antioxidant capacity. Bragantia, 79, 502-511.
Batziakas, K. G., Stanley, H., Batziakas, A. G., Brecht, J. K., Rivard, C. L., & Pliakoni, E. D. (2020). Reducing postharvest food losses in organic spinach with the implementation of high tunnel production systems. Agronomy for Sustainable Development, 40(6), 42.
Bua, C., Adami, D., & Giordano, S. (2024). GymHydro: An innovative modular small-scale smart agriculture system for hydroponic greenhouses. Electronics, 13(7), 1366.
Bukhari, S. A. B. H., Lalarukh, I., Amjad, S. F., Mansoora, N., Naz, M., Naeem, M., & Fahad, S. (2021). Drought stress alleviation by potassium-nitrate-containing chitosan/montmorillonite microparticles confers changes in Spinacia oleracea L. Sustainability, 13(17), 9903.
Chaudhary, S., Devi, P., HanumanthaRao, B., Jha, U. C., Sharma, K. D., Prasad, P. V., & Nayyar, H. (2022). Physiological and molecular approaches for developing thermotolerance in vegetable crops: a growth, yield and sustenance perspective. Frontiers in Plant Science, 13, 878498.
Desoky, E. S. M., Mansour, E., Ali, M. M., Yasin, M. A., Abdul-Hamid, M. I., Rady, M. M., & Ali, E. F. (2021). Exogenously used 24-epibrassinolide promotes drought tolerance in maize hybrids by improving plant and water productivity in an arid environment. Plants, 10(2), 354.
Dietz, K. J., Zörb, C., & Geilfus, C. M. (2021). Drought and crop yield. Plant Biology, 23(6), 881-893.
Fontanet, M., Fernàndez-Garcia, D., Rodrigo, G., Ferrer, F., & Villar, J. M. (2022). Combined simulation and optimization framework for irrigation scheduling in agriculture fields. Irrigation science, 40(1), 115-130.
Fussy, A., & Papenbrock, J. (2022). An overview of soil and soilless cultivation techniques—chances, challenges and the neglected question of sustainability. Plants, 11(9), 1153.
Gawronski, S., & Skapski, H. (1976). The optimum spacing for spinach grown in weed-free conditions.
Hogeboom, R. J. (2020). The water footprint concept and water's grand environmental challenges. One Earth, 2(3), 218-222.
Jamieson, P. D., Porter, J. R., & Wilson, D. R. (1991). A test of the computer simulation model ARCWHEAT1 on wheat crops grown in New Zealand. Field crops research, 27(4), 337-350.
Kovár, M., & Olsovská, K. (2020). Mechanisms of drought resistance in common spinach (Spinacia oleracea L.) and New Zealand spinach (Tetragonia tetragonoides (Pall.) Kuntze) plants under soil dehydration. Journal of Central European Agriculture, 21(2), 275-284.
Lawson, T., & Matthews, J. (2020). Guard cell metabolism and stomatal function. Annual review of plant biology, 71(1), 273-302.
Lee, T., Jang, W. S., Chun, B., Ahmad, M. J., Jung, Y., Kim, J., & Shin, Y. (2023). Development of irrigation schedule and management model for sustaining optimal crop production under agricultural drought. Paddy and Water Environment, 21(1), 31-45.
Liang, Z., Liu, X., Xiao, J., & Liu, C. (2021). Review of conceptual and systematic progress of precision irrigation. International Journal of Agricultural and Biological Engineering, 14(4), 20-31.
Masseroni, D., Gangi, F., Ghilardelli, F., Gallo, A., Kisekka, I., & Gandolfi, C. (2024). Assessing the water conservation potential of optimized surface irrigation management in Northern Italy. Irrigation Science, 42(1), 75-97.
Mehmood, F., Wang, G., Abubakar, S. A., Zain, M., Rahman, S. U., Gao, Y., & Duan, A. (2023). Optimizing irrigation management sustained grain yield, crop water productivity, and mitigated greenhouse gas emissions from the winter wheat field in North China Plain. Agricultural Water Management, 290, 108599.
Mishra, N., Jiang, C., Chen, L., Paul, A., Chatterjee, A., & Shen, G. (2023). Achieving abiotic stress tolerance in plants through antioxidative defense mechanisms. Frontiers in Plant Science, 14, 1110622.
Muhammad, I., Shalmani, A., Ali, M., Yang, Q. H., Ahmad, H., & Li, F. B. (2021). Mechanisms regulating the dynamics of photosynthesis under abiotic stresses. Frontiers in plant science, 11, 615942.
Naseem, J., Shah, A. A., Usman, S., Ahmed, S., Gatasheh, M. K., Shaffique, S., & Javad, S. (2025). Green synthesized FeNPs ameliorate drought stress in Spinacia oleracea L. through improved photosynthetic capacity, redox balance, and antioxidant defense. Scientific Reports, 15(1), 1782.
Nikolaou, G., Neocleous, D., Christou, A., Kitta, E., & Katsoulas, N. (2020). Implementing sustainable irrigation in water-scarce regions under the impact of climate change. Agronomy, 10(8), 1120.
Parkash, V., & Singh, S. (2020). A review on potential plant-based water stress indicators for vegetable crops. Sustainability, 12(10), 3945.
Preite, L., Solari, F., & Vignali, G. (2023). Technologies to optimize the water consumption in agriculture: A systematic review. Sustainability, 15(7), 5975.
Rahimikhoob, H., Sohrabi, T., & Delshad, M. (2020). Assessment of reference evapotranspiration estimation methods in controlled greenhouse conditions. Irrigation Science, 38, 389-400.
Ramezanifar, H., Yazdanpanah, N., Golkar Hamzee Yazd, H., Tavousi, M., & Mahmoodabadi, M. (2022). Synergistic and antagonistic interactions of soil water potential and osmotic potential linked to nitrogen fertilization on spinach traits and water use efficiency. Journal of Plant Nutrition, 45(3), 389-412.
Schlering, C., Zinkernagel, J., Dietrich, H., Frisch, M., & Schweiggert, R. (2020). Alterations in the Chemical Composition of Spinach (Spinacia oleracea L.) as Provoked by Season and Moderately Limited Water Supply in Open Field Cultivation. Horticulturae, 6(2), 25. https://doi.org/10.3390/horticulturae6020025
Seymen, M., Yavuz, D., Can, H., Kıymacı, G., Türkmen, Ö., Paksoy, M., ... & Kurtar, E. S. (2024). Molecular and physiological responses to exogenously applied melatonin in spinach under deficit irrigation conditions. Journal of Plant Growth Regulation, 43(6), 1858-1874.
Taghvaeian, S., Andales, A. A., Allen, L. N., Kisekka, I., O’Shaughnessy, S. A., Porter, D. O., & Aguilar, J. (2020). Irrigation scheduling for agriculture in the United States: The progress made and the path forward. Transactions of the ASABE, 63(5), 1603-1618.
Tzanakakis, V. A., Angelakis, A. N., Paranychianakis, N. V., Dialynas, Y. G., & Tchobanoglous, G. (2020). Challenges and opportunities for sustainable management of water resources in the island of Crete, Greece. Water, 12(6), 1538.
Uçgun, K., Ferreira, J. F., Liu, X., da Silva Filho, J. B., Suarez, D. L., Lacerda, C. F. D., & Sandhu, D. (2020). Germination and growth of spinach under potassium deficiency and irrigation with high-salinity water. Plants, 9(12), 1739.
Wabela, K., Hammani, A., Abdelilah, T., Tekleab, S., & El-Ayachi, M. (2022). Optimization of irrigation scheduling for improved irrigation water management in Bilate Watershed, Rift Valley, Ethiopia. Water, 14(23), 3960.
Wahab, A., Abdi, G., Saleem, M. H., Ali, B., Ullah, S., Shah, W., ... & Marc, R. A. (2022). Plants’ physio-biochemical and phyto-hormonal responses to alleviate the adverse effects of drought stress: A comprehensive review. Plants, 11(13), 1620.
Wang, X. (2022). Managing land carrying capacity: Key to achieving sustainable production systems for food security. Land, 11(4), 484.
Willmott, C. J. (1982). Some comments on the evaluation of model performance. Bulletin of the American Meteorological Society, 63(11), 1309-1313.
Yan, H., Deng, S., Zhang, C., Wang, G., Zhao, S., Li, M., & Zhou, Y. (2023). Determination of energy partition of a cucumber grown Venlo-type greenhouse in southeast China. Agricultural Water Management, 276, 108047.
Yang, X., Lu, M., Wang, Y., Wang, Y., Liu, Z., & Chen, S. (2021). Response mechanism of plants to drought stress. Horticulturae, 7(3), 50.
Zhao, B., Ata-Ul-Karim, S. T., Lemaire, G., Schmidhalter, U., Duan, A., Qin, A., & Liu, Z. (2022). Determining the plant critical saturated water accumulation curve in maize. Field Crops Research, 284, 108556.
Zhao, Y., Li, G., Li, S., Luo, Y., & Bai, Y. (2024). A review on the optimization of irrigation schedules for farmlands based on a simulation–optimization model. Water, 16(17), 2545.
Zhuang, T., Zhao, B., Ata-UI-Karim, S. T., Lemaire, G., Liu, X., Tian, Y., & Cao, Q. (2024). Can the allometric relationship between saturated water accumulation and dry mass be used to diagnose the water status of winter wheat?. Field Crops Research, 315, 109474.
Zhuang, T., Zhao, B., Ata-Ul-Karim, S. T., Lemaire, G., Liu, X., Tian, Y., & Cao, Q. (2025). Exploring the allometry between ear saturated water accumulation and dry mass for diagnosing winter wheat water status during the reproductive growth. Agricultural Water Management, 309, 109364.
Iranian Journal of Soil and Water Research
Volume 57, Issue 2
May 2026
Pages 431-448

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