Maize Genomics and Genetics 2025, Vol.16, No.1, 20-33 http://cropscipublisher.com/index.php/mgg 28 and fertilization could achieve high grain yield and economic benefits while minimizing soil nitrate residue (Yan et al., 2021). Specifically, an irrigation amount of 447 mm~452 mm and a fertilization rate of 290 kg/ha~303 kg/ha resulted in the highest grain yield and economic benefit, reaching a 95% confidence interval of their maximum values simultaneously (Yan et al., 2021). In another study, optimizing nitrogen management (Opt. N) at an average rate of 160 kg N/ha over a 12-year period resulted in the highest average grain yield and grain protein yield among five different N treatments. This optimized approach also reduced various environmental impacts and health risks, while enhancing economic benefits (Zhang et al., 2023). Similarly, the Nutrient Expert (NE) management system not only increased grain yields but also reduced nitrogen and carbon footprints, demonstrating its economic viability and environmental sustainability (Huang et al., 2021). 8.3 Recommendations for agricultural practices balancing yield with environmental protection To balance high maize yields with environmental protection, it is essential to adopt integrated nutrient management strategies. One effective approach is the use of split fertilization and deep placement of fertilizers, which have been shown to increase grain yield and reduce fertilizer-N loss consistently (Quan et al., 2021). Additionally, combining organic and inorganic fertilizers can significantly enhance water use efficiency and reduce the environmental footprint of maize production (Shi et al., 2023). Farmers should also consider adopting advanced agronomic practices such as ridge-furrow planting and mulching film, which have been found to optimize water and nutrient use efficiency (Shi et al., 2023). Moreover, the Nutrient Expert (NE) management system, which integrates optimized nutrient management with improved plant density, offers a sustainable solution for maintaining high yields while minimizing environmental impacts (Huang et al., 2021). By implementing these practices, farmers can achieve sustainable maize production that balances economic benefits with environmental protection. 9 Future Research Directions and Technological Innovations 9.1 Precision density and fertilization strategies based on data and AI The integration of data analytics and artificial intelligence (AI) in agriculture holds significant promise for optimizing planting density and fertilization strategies in maize cultivation. Precision agriculture technologies can analyze vast amounts of data from field sensors, satellite imagery, and historical crop performance to determine the optimal planting density and fertilization schedules. For instance, studies have shown that specific planting densities and fertilization modes can significantly impact maize yield and nutrient use efficiency. By leveraging AI, farmers can dynamically adjust these parameters to maximize yield and minimize resource use (Xu et al., 2017; Ren et al., 2020a; Li et al., 2021). Moreover, AI-driven models can predict the outcomes of different planting and fertilization strategies under varying environmental conditions. This predictive capability is crucial for adapting to climate change and ensuring sustainable agricultural practices. For example, the Decision Support System for Agrotechnology Transfer (DSSAT) has been used to simulate the effects of different nitrogen fertilizer inputs and planting densities, demonstrating the potential for AI to enhance decision-making in maize cultivation (Ren et al., 2020b). Future research should focus on developing more sophisticated AI models that can integrate real-time data and provide actionable insights for farmers. 9.2 Breeding high-efficiency nutrient use varieties for high-density planting conditions Breeding maize varieties that are efficient in nutrient use and tolerant to high-density planting is essential for improving productivity and sustainability. High-density planting often triggers a shade avoidance response in maize, leading to increased plant height and lodging, which can reduce yield. Recent advances in understanding the genetic and molecular mechanisms underlying these responses have paved the way for breeding maize with traits such as reduced plant height, more erect leaf angles, and stronger root systems (Jafari et al., 2023). For instance, breeding programs have successfully developed maize hybrids that perform well under high-density and low-nitrogen conditions, demonstrating the potential for genetic improvements to enhance nutrient use
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