Maize Genomics and Genetics 2025, Vol.16, No.1, 20-33 http://cropscipublisher.com/index.php/mgg 25 For K, studies suggest that soil application of K at a rate of up to 90 kg/ha in two equal splits (50% at sowing and 50% at knee height) is effective in improving maize growth and productivity under semiarid climates (Amanullah et al., 2016). Early foliar application of K during the vegetative stage is also recommended to enhance growth and yield under moisture stress conditions. These strategies ensure that P and K are available to the plants at critical growth stages, thereby optimizing nutrient use efficiency and crop performance. 6 Interaction between Planting Density and Fertilization 6.1 Influence of planting density on nutrient competition and fertilization needs High planting density in maize cultivation can significantly influence nutrient competition among plants. As plant density increases, the competition for essential nutrients such as nitrogen (N), phosphorus (P), and potassium (K) intensifies, which can negatively impact plant growth and productivity. For instance, high-density planting has been shown to aggravate competition among maize plants, leading to reduced nutrient uptake and lower grain yields (Liu et al., 2016). Additionally, nutrient spatial heterogeneity can exacerbate root competition, further decreasing maize yield at high planting densities (Li et al., 2018). Moreover, the form of nitrogen supplied can also affect nutrient uptake efficiency under different planting densities. A mixed supply of nitrate (NO3 -) and ammonium (NH4 +) has been found to improve plant growth and nutrient uptake efficiency, particularly under high planting densities. This mixed nitrogen form increases energy use efficiency, thereby enhancing biomass production and nutrient absorption (Figure 3) (Wang et al., 2019). Therefore, understanding the interaction between planting density and nutrient competition is crucial for optimizing fertilization strategies in high-density maize cultivation. 6.2 Optimization strategies for appropriate fertilization at high planting densities To optimize fertilization at high planting densities, it is essential to adjust the type and timing of fertilizer application. Slow-released fertilizers (SF) have been shown to be more effective than conventional fertilizers (CF) in high-density maize planting. SF can increase post-silking dry matter accumulation and promote nutrient uptake, resulting in higher grain yields and nutrient use efficiencies (Li et al., 2021). Additionally, the application of plant growth regulators in combination with nitrogen fertilization can enhance nutrient absorption and translocation, further improving grain yield and quality in high-density planting (Liu et al., 2016). Another effective strategy is to reduce the nitrogen application rate while increasing planting density. Studies have demonstrated that a 30% increase in planting density combined with a 15% reduction in nitrogen rate can enhance nitrogen partial factor productivity and maize grain yield (Du et al., 2021). This approach not only improves yield but also promotes sustainable agricultural practices by reducing excessive nitrogen use. Therefore, optimizing fertilization strategies at high planting densities involves a combination of slow-released fertilizers, plant growth regulators, and adjusted nitrogen application rates. 6.3 Adjustments in fertilization techniques based on density conditions Adjusting fertilization techniques based on planting density conditions is crucial for achieving high maize yields and efficient nutrient use. At lower planting densities, a higher nitrogen application rate may be required to maximize yield. For example, under a planting density of 7.5 plants m2, the recommended nitrogen application rate is 340 kg/ha, with a distribution ratio of 61.2% before silking and 38.8% after silking (Zhai et al., 2022). In contrast, at higher planting densities, the nitrogen application rate should be increased to 380 kg/ha, with a distribution ratio of 65.8% before flowering and 34.2% after flowering (Zhai et al., 2022). Furthermore, the timing of nitrogen application is critical. Sidedress nitrogen fertilization at different growth stages can significantly impact nitrogen uptake and grain yield. Higher plant densities have been shown to increase pre-silking nitrogen uptake, which is crucial for achieving high yields (Ciampitti and Vyn, 2011). Therefore, adjusting the timing and rate of nitrogen application based on planting density can optimize nutrient use efficiency and improve maize productivity.
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