Univrsity of Tehran Press Iranian Journal of Field Crop Science 2008-4811 56 4 2025 12 22 Integrated Application of Effective Microorganisms and Urea on Physiological, Biochemical, Photosynthetic Pigments Traits of Different Maize Cultivars under Water Deficit Stress Conditions Integrated Application of Effective Microorganisms and Urea on Physiological, Biochemical, Photosynthetic Pigments Traits of Different Maize Cultivars under Water Deficit Stress Conditions 33 51 105540 10.22059/ijfcs.2025.395531.655139 FA Kamyab Hosseini Department of Agrotechnology, Faculty of Agriculture, University of Tarbiat Modares, Tehran, Iran 0009-0000-4944-6984 Ali Heidarzadeh Department of Agrotechnology, Faculty of Agriculture, University of Tarbiat Modares, Tehran, Iran 0000-0001-6680-9257 Ali Sorooshzadeh Department of Agrotechnology, Faculty of Agriculture, University of Tarbiat Modares, Tehran, Iran 0000-0002-5840-2681 Journal Article 2025 05 19 Introduction. Maize (Zea mays L.) is one of the most important cereal crops globally, serving as a staple food and a key component in animal feed and biofuel production. However, its productivity is significantly influenced by environmental stresses, especially water deficit. Water scarcity affects the physiological and biochemical functioning of maize, leading to reduced photosynthetic efficiency and ultimately lower yield. In recent years, climate change and irregular rainfall patterns have increased the frequency of drought events, further emphasizing the need for sustainable agricultural practices to enhance crop resilience. Among the various approaches developed to mitigate drought stress in crops, the use of biological agents such as effective microorganisms (EM) has gained attention. EM consists of a mixture of beneficial microorganisms including nitrogen-fixing bacteria, phosphate-solubilizing bacteria, lactic acid bacteria, and yeasts, which improve plant growth by enhancing nutrient availability, root development, and stress resistance. Additionally, nitrogen (N) fertilizer plays a crucial role in plant metabolism, but its excessive use has resulted in serious environmental concerns such as groundwater contamination, eutrophication, and increased greenhouse gas emissions. Thus, the integration of EM with N fertilizer presents a promising strategy to reduce chemical input while maintaining or improving crop performance. This study aimed to evaluate the combined effects of EM and nitrogen fertilizer on photosynthetic pigments and biochemical traits of two maize cultivars under different irrigation regimes. The research specifically investigated how this integration can enhance maize tolerance to water deficit and improve physiological traits contributing to yield. Materials and Methods. The field experiment was conducted during the growing season of 2023 at the Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. The experimental design was a split-split-plot layout based on a randomized complete block design (RCBD) with three replications. The main plots included three irrigation regimes based on soil field capacity: 85% (optimal irrigation), 70% (moderate water deficit), and 55% (severe water deficit). The subplots were assigned to three nutritional systems: Nitrogen fertilizer (urea), effective microorganisms (EM), and integrated treatment of EM + nitrogen fertilizer. The sub-subplots included two maize cultivars: S.C. 704, and TWC. 647. During the experiment, data were collected on several physiological and biochemical parameters including carotenoid content, intercellular to ambient CO₂ ratio (Ci/Ca), anthocyanins, total phenolics, proline, and seed yield. Standard laboratory protocols were followed for pigment extraction and biochemical analyses. Statistical analysis was performed using analysis of variance (ANOVA), and treatment means were compared using the least significant difference (LSD) test at a 5% significance level. Results and Discussion. The results demonstrated that both irrigation regime and fertilizer treatment significantly affected the physiological and biochemical traits of maize. Under optimal irrigation (85% field capacity), the integrated application of EM and nitrogen fertilizer resulted in the highest carotenoid content and Ci/Ca ratio, particularly in the S.C. 704 cultivar. This indicates improved photosynthetic activity and gas exchange efficiency due to the synergistic effects of EM and nitrogen. Also, anthocyanin content was significantly increased (by 27%) in both cultivars under optimal irrigation when treated with the integrated EM + nitrogen fertilizer compared to the nitrogen-only control. This suggests enhanced antioxidant capacity under favorable water conditions. Under severe water deficit (55% field capacity), there was a notable increase in total phenolic and proline contents, with S.C. 704 showing a stronger biochemical response than TWC. 647. Phenolics play a critical role in plant defense against oxidative stress, while proline acts as an osmoprotectant, stabilizing proteins and membranes under drought conditions. The highest phenolic content was observed in S.C. 704 under the combined influence of water stress and EM application. Similarly, S.C. 704 accumulated significantly more proline than TWC. 647, confirming its superior drought tolerance. These results highlight the cultivar-dependent responses to stress and indicate the potential of EM in enhancing biochemical defense mechanisms. Seed yield was significantly influenced by the treatments. The highest yield (9,708 kgha⁻¹) was obtained from the S.C. 704 cultivar under optimal irrigation with the integrated EM and nitrogen treatment. This emphasizes the practical benefit of combining EM with chemical fertilizers to sustain or improve yield under ideal water availability. Overall, S.C. 704 consistently outperformed TWC. 647 in terms of pigment accumulation, stress-related biochemical traits, and yield, suggesting its suitability for cultivation under both optimal and stressful conditions when supported by integrated nutrient management. Conclusion. The integration of effective microorganisms with nitrogen fertilizer proved to be a beneficial strategy for improving the physiological and biochemical traits, and maize yield under varying irrigation conditions. While the use of nitrogen fertilizer alone supports growth, combining it with EM enhances nutrient uptake, boosts antioxidant production, and strengthens drought resilience, especially in the S.C. 704 cultivar. Under optimal irrigation, the integrated treatment significantly improved carotenoid levels, anthocyanin content, and yield. Under severe water stress, EM application mitigated stress-induced damage by increasing phenolic and proline levels, again more notably in S.C. 704. These findings confirm the role of EM in enhancing maize tolerance to drought while offering an environmentally sustainable approach to reduce chemical fertilizer dependency. Given the global concerns about the environmental impacts of excessive fertilizer use, the combined application of EM and nitrogen represents a promising approach for sustainable maize production. Future studies should explore the long-term effects of this integration on soil health, microbial diversity, and yield stability across different agroecological zones. Introduction. Maize (Zea mays L.) is one of the most important cereal crops globally, serving as a staple food and a key component in animal feed and biofuel production. However, its productivity is significantly influenced by environmental stresses, especially water deficit. Water scarcity affects the physiological and biochemical functioning of maize, leading to reduced photosynthetic efficiency and ultimately lower yield. In recent years, climate change and irregular rainfall patterns have increased the frequency of drought events, further emphasizing the need for sustainable agricultural practices to enhance crop resilience. Among the various approaches developed to mitigate drought stress in crops, the use of biological agents such as effective microorganisms (EM) has gained attention. EM consists of a mixture of beneficial microorganisms including nitrogen-fixing bacteria, phosphate-solubilizing bacteria, lactic acid bacteria, and yeasts, which improve plant growth by enhancing nutrient availability, root development, and stress resistance. Additionally, nitrogen (N) fertilizer plays a crucial role in plant metabolism, but its excessive use has resulted in serious environmental concerns such as groundwater contamination, eutrophication, and increased greenhouse gas emissions. Thus, the integration of EM with N fertilizer presents a promising strategy to reduce chemical input while maintaining or improving crop performance. This study aimed to evaluate the combined effects of EM and nitrogen fertilizer on photosynthetic pigments and biochemical traits of two maize cultivars under different irrigation regimes. The research specifically investigated how this integration can enhance maize tolerance to water deficit and improve physiological traits contributing to yield. Materials and Methods. The field experiment was conducted during the growing season of 2023 at the Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. The experimental design was a split-split-plot layout based on a randomized complete block design (RCBD) with three replications. The main plots included three irrigation regimes based on soil field capacity: 85% (optimal irrigation), 70% (moderate water deficit), and 55% (severe water deficit). The subplots were assigned to three nutritional systems: Nitrogen fertilizer (urea), effective microorganisms (EM), and integrated treatment of EM + nitrogen fertilizer. The sub-subplots included two maize cultivars: S.C. 704, and TWC. 647. During the experiment, data were collected on several physiological and biochemical parameters including carotenoid content, intercellular to ambient CO₂ ratio (Ci/Ca), anthocyanins, total phenolics, proline, and seed yield. Standard laboratory protocols were followed for pigment extraction and biochemical analyses. Statistical analysis was performed using analysis of variance (ANOVA), and treatment means were compared using the least significant difference (LSD) test at a 5% significance level. Results and Discussion. The results demonstrated that both irrigation regime and fertilizer treatment significantly affected the physiological and biochemical traits of maize. Under optimal irrigation (85% field capacity), the integrated application of EM and nitrogen fertilizer resulted in the highest carotenoid content and Ci/Ca ratio, particularly in the S.C. 704 cultivar. This indicates improved photosynthetic activity and gas exchange efficiency due to the synergistic effects of EM and nitrogen. Also, anthocyanin content was significantly increased (by 27%) in both cultivars under optimal irrigation when treated with the integrated EM + nitrogen fertilizer compared to the nitrogen-only control. This suggests enhanced antioxidant capacity under favorable water conditions. Under severe water deficit (55% field capacity), there was a notable increase in total phenolic and proline contents, with S.C. 704 showing a stronger biochemical response than TWC. 647. Phenolics play a critical role in plant defense against oxidative stress, while proline acts as an osmoprotectant, stabilizing proteins and membranes under drought conditions. The highest phenolic content was observed in S.C. 704 under the combined influence of water stress and EM application. Similarly, S.C. 704 accumulated significantly more proline than TWC. 647, confirming its superior drought tolerance. These results highlight the cultivar-dependent responses to stress and indicate the potential of EM in enhancing biochemical defense mechanisms. Seed yield was significantly influenced by the treatments. The highest yield (9,708 kgha⁻¹) was obtained from the S.C. 704 cultivar under optimal irrigation with the integrated EM and nitrogen treatment. This emphasizes the practical benefit of combining EM with chemical fertilizers to sustain or improve yield under ideal water availability. Overall, S.C. 704 consistently outperformed TWC. 647 in terms of pigment accumulation, stress-related biochemical traits, and yield, suggesting its suitability for cultivation under both optimal and stressful conditions when supported by integrated nutrient management. Conclusion. The integration of effective microorganisms with nitrogen fertilizer proved to be a beneficial strategy for improving the physiological and biochemical traits, and maize yield under varying irrigation conditions. While the use of nitrogen fertilizer alone supports growth, combining it with EM enhances nutrient uptake, boosts antioxidant production, and strengthens drought resilience, especially in the S.C. 704 cultivar. Under optimal irrigation, the integrated treatment significantly improved carotenoid levels, anthocyanin content, and yield. Under severe water stress, EM application mitigated stress-induced damage by increasing phenolic and proline levels, again more notably in S.C. 704. These findings confirm the role of EM in enhancing maize tolerance to drought while offering an environmentally sustainable approach to reduce chemical fertilizer dependency. Given the global concerns about the environmental impacts of excessive fertilizer use, the combined application of EM and nitrogen represents a promising approach for sustainable maize production. Future studies should explore the long-term effects of this integration on soil health, microbial diversity, and yield stability across different agroecological zones.

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