Legume Genomics and Genetics 2024, Vol.15, No.6, 303-314 http://cropscipublisher.com/index.php/lgg 308 have also shown promise in managing pest populations. Despite the challenges in large-scale application, integrating biocontrol with other management practices can lead to sustainable pest and disease management in soybean cultivation (Khan et al., 2019; Bueno et al., 2023). 6 Planting Techniques and Row Spacing 6.1 Optimum plant density for yield maximization Optimizing plant density is crucial for maximizing soybean yield. High plant density can enhance canopy light interception and dry matter accumulation, leading to increased productivity. For instance, a study demonstrated that higher planting density (2.7 × 10^5 plants·ha-¹) significantly increased canopy light interception and dry matter accumulation, resulting in a 22.8% yield increase compared to normal planting density (Xu et al., 2021). Similarly, another research indicated that a seeding rate of 457 000 seeds·ha⁻¹ combined with narrow row spacing improved yield by 26% and provided a substantial profit margin over conventional practices (Schmitz and Kandel, 2021). However, the response to plant density can vary with cultivar and environmental conditions, as observed in a study from Japan where narrow intra-row spacing increased yield in some cultivars but not others due to factors like leaf area index and lodging susceptibility (Kumagai, 2020). 6.2 Row spacing and its impact on light utilization Row spacing is a critical factor influencing light utilization and, consequently, soybean yield. Narrow row spacing tends to expedite canopy closure, which enhances light interception and reduces weed competition. For example, early planted soybeans with narrow row spacing (38 cm) reached 90% green canopy cover faster and yielded more compared to wider row spacing (Arsenijevic et al., 2021). Another study found that narrow row spacing (30 cm) increased yield by 302 kg·ha⁻¹ compared to wider spacing (76 cm). Additionally, uniform plant distribution within rows can further improve light interception and yield. Research showed that uniform plant spacing increased canopy light interception and dry matter accumulation, leading to a 9.5% yield increase over non-uniform spacing (Xu et al., 2021). However, the benefits of narrow row spacing can be influenced by other factors such as soil conditions and management practices (Masino et al., 2018). 6.3 Planting date and sowing depth considerations The timing of planting and sowing depth are pivotal in determining soybean yield. Early planting generally results in higher yields due to extended growing periods and better utilization of environmental resources. Studies have shown that planting soybeans earlier in the season (late April) can significantly increase yield compared to standard planting times (late May) (Arsenijevic et al., 2021). For instance, early planting combined with narrow row spacing and high seeding rates improved yield by 26% in North Dakota (Schmitz and Kandel, 2021). Additionally, the interaction between planting date and cultivar maturity is crucial. Delayed planting shortens the growing period, reducing radiation and growing degree day accumulation, which negatively impacts yield. Therefore, planting before 20 May is recommended to maximize yield potential (Kessler et al., 2020). Sowing depth, although not extensively covered in the provided studies, should be optimized to ensure proper seedling emergence and establishment, which are critical for achieving high yields. 7 Genetic and Biological Enhancements 7.1 Role of genotype selection in agronomic optimization Genotype selection plays a crucial role in optimizing agronomic performance and yield in soybean cultivation. The genetic architecture of soybean yield and key agronomic traits has been extensively studied, revealing significant marker-trait associations that can be leveraged for breeding programs. For instance, a Nested Association Mapping (NAM) population study identified 23 significant marker-trait associations for yield, demonstrating the value of expanding the genetic base of US soybean breeding (Diers et al., 2018). Additionally, genome-wide association studies (GWAS) have identified numerous Single Nucleotide Polymorphisms (SNPs) associated with traits such as maturity, plant height, and seed weight, which contribute to yield improvement (Ravelombola et al., 2021). These findings underscore the importance of selecting genotypes with desirable traits to enhance soybean yield.
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