Field Crop 2024, Vol.7, No.3, 158-170 http://cropscipublisher.com/index.php/fc 161 indirectly increasing the protein content in maize. Appropriate soil management practices, such as the application of organic fertilizers and the use of crop residue mulching, can improve soil fertility and microbial activity, further promoting the accumulation of protein in maize. 3.4 Planting density and spacing Planting density and spacing significantly affect maize protein content by influencing nutrient uptake and plant growth. Higher planting densities, when combined with appropriate fertilization and soil management practices, can lead to increased nitrogen accumulation and higher grain protein content (Liu et al., 2018; Zhou et al., 2019). Optimized planting density ensures better light interception and nutrient utilization, which are essential for protein synthesis in maize. Studies have shown that integrated agronomic practices, including optimal planting density, can enhance root growth and development, thereby improving nitrogen uptake and protein content in maize (Vanlauwe et al., 2011; Liu et al., 2017). Reasonable planting density can optimize the utilization of light, water, and nutrients, promoting the healthy growth of maize. Studies have shown that appropriately reducing planting density can increase nutrient supply per plant, thereby enhancing the protein content in grains (Andrade and Abbate, 2005). However, excessively low planting density may lead to decreased land use efficiency. Therefore, it is essential to find a balance to ensure both high yield and high protein content. 4 Agronomic Practices Affecting Maize Starch Content 4.1 Fertilization and nutrient management Fertilization and nutrient management play a crucial role in determining the starch content in maize. Studies have shown that nitrogen fertilization can influence starch properties, although its impact is less pronounced compared to its effect on protein content. For instance, nitrogen levels have been found to affect the amylose-amylopectin ratio, with higher nitrogen levels generally leading to increased amylopectin content and decreased amylose content (Kaplan et al., 2019). Additionally, the use of slow-release fertilizers versus conventional fertilizers can result in different starch characteristics, such as granule size and crystallinity, which are essential for the functional properties of maize starch (Figure 1) (Wang and Lu, 2022). Integrated agronomic practices, including optimal fertilization strategies, have also been shown to enhance maize yield and nitrogen use efficiency, indirectly affecting starch accumulation (Liu et al., 2018; Zhou et al., 2019). Wang and Lu (2020) studied the volume percentage, average granule size, and relative crystallinity of starch granules in maize varieties JY877 and SY30 under no fertilization (0F), conventional fertilization (CF), and slow-release fertilization (SF) conditions. The results showed that fertilization significantly increased the average size of starch granules, with no significant difference between CF and SF treatments. Conventional fertilization (CF) significantly increased the relative crystallinity of starch, while the slow-release fertilization (SF) treatment did not show a significant difference compared to no fertilization (0F). In summary, different fertilization modes significantly affect the size and crystallinity of maize starch granules, with conventional fertilization having the most significant effect. 4.2 Irrigation practices Irrigation practices significantly impact maize starch content. Different irrigation levels can alter the total starch accumulation in maize. For example, a study found that the highest starch values were obtained from a combination of moderate irrigation and high nitrogen levels, while the lowest starch levels were recorded under full irrigation with lower nitrogen levels (Kaplan et al., 2019). Moreover, the timing and frequency of irrigation can influence starch properties. Nighttime irrigation and low-frequency irrigation have been associated with higher mycotoxin levels, which can indirectly affect starch quality (Herrera et al., 2023). Therefore, optimizing irrigation practices is essential for maintaining high starch content and quality in maize. 4.3 Timing of planting and harvesting The timing of planting and harvesting is another critical factor affecting maize starch content. Early planting can lead to better starch accumulation due to longer growing periods and optimal use of available resources.
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