Field Crop 2024, Vol.7, No.4, 222-231 http://cropscipublisher.com/index.php/fc 226 4.2 Improvement of micronutrient content (e.g., iron, zinc) The application of mineral fertilizers also plays a crucial role in improving the micronutrient content of maize. Long-term nitrogen fertilization has been shown to increase the concentration of essential micronutrients such as iron (Fe) and manganese (Mn) in maize grains, although it may decrease zinc (Zn) concentration due to yield dilution (Miner et al., 2018). Soil application of zinc fertilizer has been particularly effective in increasing the zinc concentration in maize grains, enhancing both yield and nutritional quality (Liu et al., 2020). Furthermore, biofortification strategies using nitrogen fertilization have been successful in increasing the concentrations of zinc and iron in maize shoots, contributing to better-quality feed (Grujcic et al., 2021). 4.3 Influence on maize bioavailability of nutrients The bioavailability of nutrients in maize can be significantly influenced by the type and application method of mineral fertilizers. For example, urea treatment has been shown to increase the potential bioavailability of zinc in maize kernels by 13.3% compared to biofertilizer treatment (Dragičević et al., 2022). Additionally, the use of bio-organic fertilizers, which combine biofertilizers with inorganic fertilizers, has been found to enhance the bioavailability of essential micronutrients such as iron, zinc, and manganese in maize (Hafez et al., 2021). The integration of plant growth-promoting rhizobacteria (PGPR) with mineral fertilizers also improves the bioavailability of nutrients, leading to better growth and nutritional quality of maize (Ahmad et al., 2023). 4.4 Case study in place: analyzing the effect of specific fertilizer applications on maize nutritional value A case study conducted in the Northern region of Ghana evaluated the impact of foliar application of macro and micronutrients on maize growth and yield. The study found that the application of nitrogen in a split form, combined with foliar application of phosphorus, zinc, and iron, produced the highest grain yield. The treatment NP2K+[P+Zn+Fe] significantly improved the leaf surface area and grain yield, demonstrating the effectiveness of balanced nutrient application in enhancing maize nutritional value (Asare, 2023). Another study in a no-till maize cropping system showed that long-term nitrogen fertilization positively impacted the concentration of iron and manganese in maize grains, although it reduced zinc concentration (Miner et al., 2018). These findings highlight the importance of region-specific fertilizer strategies to optimize maize nutritional value. Figure 2 Effect of fertilizer treatment on SPAD values. Error bars represent Standard Error of Means (SEM). Bars of the same design and colour with similar letters on top are not significantly different (Adopted from Asare, 2023) Asare, (2023) examines the impact of different fertilizer treatments on the SPAD values of maize, which indicate chlorophyll content and plant nitrogen status. At week 8, there were no significant differences across treatments.
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