1
Harran University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, Sanliurfa
2
Harran University, Faculty of Agriculture, Department of Field Crops, Sanliurfa
Abstract
This study aimed to evaluate the responses of cowpea (Vigna unguiculata L.) to various fertilizer treatments and to determine the applicability of sensor-based measurements including SPAD, Normalized Difference Vegetation Index (NDVI), and thermal imaging in monitoring fertilizer efficiency. The experiment was conducted in the research greenhouse of Harran University Faculty of Agriculture using a Completely Randomized Design (CRD) with five treatments and three replications. Urea application resulted in the highest physiological improvement, increasing chlorophyll content (SPAD +25%), canopy vigor (NDVI +18%), and plant height (+22%), and produced the greatest biomass accumulation (fresh weight: 5.8 g plant⁻¹; dry weight; 1.8 g plant⁻¹). Microbial fertilizer moderately enhanced chlorophyll content (SPAD +12%) and canopy vigor (NDVI +10%). Iron treatment increased plant moisture content to 86% while reducing dry matter percentage to 27%, indicating its distinct influence on water-use dynamics. Thermal imaging showed that canopy temperatures reached ~42 °C in the control, whereas urea and microbial treatments maintained lower temperatures (35–37 °C), reflecting improved transpiration and reduced heat stress. Correlation analysis revealed strong positive associations between biomass (fresh and dry weight) and SPAD and NDVI values (r=0.82–0.89; p<0.01). Principal component analysis (PCA) explained 74.6% of the total variation in physiological (SPAD, NDVI, canopy temperature), morphological (plant height), and harvest-related traits, clearly separating the urea treatment along the biomass–photosynthetic activity axis. Overall, urea proved to be the most effective fertilization strategy for improving physiological performance and biomass production in cowpea; microbial fertilizers provided a sustainable alternative; and iron played a decisive role in plant water relations. Furthermore, sensor-based parameters (SPAD, NDVI, thermal imaging) were demonstrated to be reliable tools for monitoring fertilizer efficiency and supporting early yield prediction.
RUFAİOĞLU, S. B., & TUNÇ, M. (2025). Sensor-Based Assessment of Cowpea Responses to Various Fertilizer Treatments Using Optical and Thermal Imaging Techniques. ISPEC Journal of Agricultural Sciences, 9(4), 1166–1181. https://doi.org/10.5281/zenodo.17906932
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Murat TUNÇ
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