Field Crop 2024, Vol.7, No.4, 222-231 http://cropscipublisher.com/index.php/fc 227 However, by weeks 10 and 12, variability increased, with the highest SPAD values observed in treatments combining NPK with additional sulfur, zinc, and iron. These results suggest that supplementing NPK with these micronutrients, particularly iron, significantly enhances chlorophyll content, likely due to iron's role in boosting photosynthesis. The findings underscore the importance of including micronutrients in fertilization strategies to improve maize growth and overall plant health, particularly in the later stages of development. By integrating various mineral fertilizers and application methods, it is possible to enhance both the macronutrient and micronutrient content of maize, thereby improving its overall nutritional value and bioavailability of essential nutrients. 5 Environmental and Economic Considerations 5.1 Sustainability of mineral fertilizer use The sustainability of mineral fertilizer use in maize production is a critical consideration, particularly in the context of long-term soil health and environmental impact. Studies have shown that substituting mineral fertilizers with organic alternatives, such as manure or compost, can significantly enhance soil organic carbon sequestration and reduce nitrogen losses. For instance, substituting mineral fertilizer with organic fertilizer increased soil organic carbon sequestration by 925 kg C ha⁻¹ yr⁻¹ and decreased the global warming potential by 116 kg CO2 eq ha⁻¹ (Wei et al., 2020). Additionally, the combined use of organic and mineral fertilizers has been found to improve maize yield and nutrient use efficiency over time, suggesting a more sustainable approach to fertilization (Zhang et al., 2018; Wei et al., 2020; Zerssa et al., 2023). 5.2 Economic impacts on smallholder and commercial maize production The economic impacts of using mineral fertilizers versus organic alternatives are significant for both smallholder and commercial maize producers. Substituting mineral fertilizers with manure has been shown to increase economic profits and eco-efficiency. For example, substituting 50% of mineral-N with solid or liquid manure increased economic profits by 17.2% and 19.1%, respectively, while also reducing environmental impacts (Li et al., 2020). Similarly, replacing 75% of mineral N fertilizer with manure significantly increased net benefits by 8.47-35.51% compared to using mineral fertilizers alone (Wang et al., 2023). These findings indicate that integrating organic fertilizers can be economically beneficial, particularly for smallholders who may have limited access to mineral fertilizers (Zerssa et al., 2023). 5.3 Potential environmental risks While mineral fertilizers are effective in boosting maize yields, their use poses several environmental risks, including soil degradation and water contamination. The application of mineral fertilizers can lead to increased greenhouse gas emissions, such as N2O and CO2, and contribute to soil acidification and aquatic eutrophication (Zhang et al., 2018; Zerssa et al., 2023). For instance, pure mineral fertilizer treatments resulted in higher N2O emissions compared to treatments with compost or manure (Zerssa et al., 2021). Additionally, long-term use of mineral fertilizers without organic amendments can lead to soil nutrient depletion and reduced soil fertility (Mustafa et al., 2021). Therefore, a balanced approach that combines mineral and organic fertilizers is recommended to mitigate these environmental risks while maintaining high maize productivity (Zhang et al., 2018; Mustafa et al., 2021). In conclusion, the integration of organic fertilizers with mineral fertilizers offers a sustainable and economically viable approach to maize production. This strategy not only enhances soil health and reduces environmental risks but also provides economic benefits to both smallholder and commercial farmers. 6 Future Directions and Innovations 6.1 Development of biofortified maize through optimized fertilizer use The development of biofortified maize through optimized fertilizer use is a promising avenue for enhancing the nutritional value of maize. Agronomic biofortification, which involves the application of mineral micronutrient fertilizers to soil or plant leaves, has shown significant potential in increasing the micronutrient content in maize grains. For instance, the application of 50% recommended dose of fertilizers (RDF) through NPK combined with
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