Open Access

ARTICLE

Soil Temperature and Moisture as Key Determinants of SPAD Values in Greenhouse-Grown Cucumber in Qatar

Farhat Abbas¹, Fahim Ullah Khan^1,2,*, Salem Al-Naemi³, Awni Al-Otoom¹, Ahmed T. Moustafa⁴, Khaled Shami¹

1 College of Engineering and Technology, University of Doha for Science and Technology, Doha, 24449, Qatar
2 Department of Agriculture, Hazara University Mansehra, Mansehra, 21120, Pakistan
3 College of Computer and Information Technology, University of Doha for Science and Technology, Doha, 24449, Qatar
4 Al Sulaiteen Agricultural Research Study and Training Center, Umm Salal Ali, Farm No 301, Doha, P.O. Box 8588, Qatar

* Corresponding Author: Fahim Ullah Khan. Email:

(This article belongs to the Special Issue: Influence of Biotic and Abiotic Stresses Signals on Plants and their Performance at Different Environments)

Phyton-International Journal of Experimental Botany 2025, 94(9), 2911-2925. https://doi.org/10.32604/phyton.2025.064239

Received 09 February 2025; Accepted 28 March 2025; Issue published 30 September 2025

Abstract

This study aimed to explore the relationship between Soil-Plant Analysis Development (SPAD) values and key environmental factors in cucumber (Cucumis sativus L.) cultivation in a greenhouse. SPAD values, indicative of chlorophyll content, reflect plant health and productivity. The analysis revealed strong positive correlations between SPAD values and both indoor light intensity (ILI, r = 0.59, p < 0.001) and outdoor light intensity (OLI, r = 0.62, p < 0.001), suggesting that higher light intensities were associated with enhanced SPAD values. In contrast, significant negative correlations were found between SPAD values and soil temperature at 15–30 cm depth (ST1530, r = −0.47, p < 0.001) and volumetric soil moisture content at the same depth (SM1530, r = −0.52, p < 0.001), with higher soil temperatures (e.g., 28°C) and excessive moisture (e.g., 25%) leading to reduced SPAD values. Multiple regression analysis identified ST1530 and SM1530 as significant negative predictors of SPAD, with coefficients of −0.97 (p = 0.05) and −0.34 (p = 0.05), respectively, suggesting that increases in soil temperature and moisture result in lower SPAD values. Indoor light intensity (e.g., 600–800 μmol/m²/s) emerged as a significant positive contributor, with a coefficient of 0.01 (p < 0.001), highlighting its role in promoting chlorophyll synthesis. Additionally, relative humidity (r = 0.27, p < 0.01) showed a positive, although less pronounced, association with SPAD. These results underscore the importance of both direct and indirect environmental factors in influencing SPAD variability and, by extension, plant health and productivity in cucumber cultivation.

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Keywords

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