Field Crop 2024, Vol.7, No.4, 222-231 http://cropscipublisher.com/index.php/fc 225 3 Types of Mineral Fertilizers 3.1 Nitrogen-based fertilizers Nitrogen-based fertilizers are crucial for maize growth as they significantly enhance nitrogen uptake and utilization efficiency. Studies have shown that the application of nitrogen fertilizers, especially when combined with organic amendments like compost or biochar, can improve maize yield, oil, starch, protein, and carbohydrate content, even under varying irrigation levels (El-Syed et al., 2023). Additionally, foliar application of nitrogen-phosphorus-potassium (NPK) fertilizers at specific growth stages has been found to significantly increase nitrogen uptake and protein content in maize (Nirere et al., 2021). 3.2 Phosphorus-based fertilizers Phosphorus is essential for energy transfer and photosynthesis in maize. The effectiveness of phosphorus fertilizers can be enhanced when used in combination with organic amendments. For instance, the application of phosphorus along with compost and organic acids in calcareous soil has been shown to significantly increase phosphorus content in maize straw and grain, thereby improving overall yield and nutritional quality (Tabbasum et al., 2020). Moreover, the combined use of phosphorus fertilizers with arbuscular mycorrhizal fungi (AMF) can enhance phosphorus availability and uptake, leading to higher maize yields (Fall et al., 2023). 3.3 Potassium-based fertilizers Potassium plays a vital role in water regulation and enzyme activation in maize. The application of potassium fertilizers, particularly when integrated with compost and organic acids, has been demonstrated to increase potassium accumulation in maize grains and improve yield and biochemical attributes (Tabbasum et al., 2020). Additionally, foliar application of NPK fertilizers has been shown to enhance potassium uptake and soil potassium levels, contributing to better maize growth and protein content (Nirere et al., 2021). 3.4 Micronutrient fertilizers Micronutrients such as zinc, iron, and manganese are essential for various physiological functions in maize. The combined application of mineral fertilizers and compost has been found to increase the concentration of these essential minerals in maize grains, thereby improving their nutritional quality. For example, replacing a portion of mineral nitrogen with compost significantly elevated the levels of iron and manganese in maize grains (Zerssa et al., 2023). Long-term application of balanced NPK fertilizers along with farmyard manure (FYM) and lime has also been shown to enhance the content of calcium, zinc, phosphorus, magnesium, and iron in maize (Thakur et al., 2020). 3.5 Synergistic effects of combined fertilizers The synergistic effects of combining mineral fertilizers with organic amendments such as compost, biochar, and organic acids have been widely documented. These combinations not only improve nutrient uptake and use efficiency but also enhance soil health and mitigate environmental impacts. For instance, the integrated use of mineral NPK fertilizers with compost and organic acids significantly increased maize yield and nutrient content while improving soil properties (Tabbasum et al., 2020). Similarly, the combination of mineral fertilizers with biochar has been shown to enhance nitrogen use efficiency and yield under drought conditions (Iqbal et al., 2022). These synergistic effects highlight the importance of integrated nutrient management strategies for sustainable maize production. 4 Impact of Mineral Fertilizers on Maize Nutritional Value 4.1 Enhancement of macronutrients (e.g., protein content) Mineral fertilizers have been shown to significantly enhance the macronutrient content of maize, particularly protein. For instance, the application of urea, a commonly used mineral fertilizer, has been found to increase the protein content in maize kernels. In a study comparing different maize genotypes and fertilizer treatments, the red-kernel hybrid maize treated with biofertilizers exhibited the highest protein accumulation, while urea treatment enhanced the antioxidant status and potential zinc bioavailability in maize kernels (Dragičević et al., 2022). Additionally, the combination of biochar with inorganic fertilizers improved the protein content and overall yield of maize, especially under drought conditions (El-Syed et al., 2023).
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