Comprehensive Analysis of Soybean Seed Physiological Quality and Factors Influencing Plant Development and Yield

Abstract

Soybean [Glycine max (L.) Merr.] is a key global crop due to its nutritional value and role in food security. Maximizing soybean yield is essential for meeting future food demands. Successful crop production begins with rapid and uniform seedlings establishment, which is strongly influenced by seed physiological quality, particularly seed vigor. Seed deterioration, a major cause of seed quality loss, can be costly for farmers, as it may lead to reduced plant density and negatively impact crop growth and yield, especially under adverse field conditions. This dissertation comprehensively analyzed the influence of seed physiological quality on soybean performance and examined its interaction with key agronomic and biological factors, including soil texture, seeding depth, and the use of microbial inoculants. Results consistently demonstrated that high seed vigor is essential to ensure adequate crop establishment, leading to faster, more uniform emergence and greater plant populations. On the contrary, low-vigor seeds caused significant delays in emergence and decreased plant density. Field evaluations of microbial inoculants applied as seed treatments across multiple seasons and locations often yielded inconsistent effects on final grain yield and economic return, though specific plant growth-promoting rhizobacteria (PGPR) strains showed potential for emergence and root biomass improvement, particularly when coupled with low-vigor seeds under greenhouse conditions. Furthermore, while high vigor seeds planted at shallow seeding depth promoted earlier seedling establishment, this early advantage frequently leveled off with the crop development. This finding underscores the significant compensatory capacity of modern soybean varieties, which often mitigated the negative effects of reduced plant density on final grain yield. Overall, this research validates improved seed quality as an essential management strategy for achieving rapid emergence and reducing crop establishment risks. Furthermore, high seed quality is an essential strategy for resilient soybean production in the face of variable environmental conditions, highlighting the need for risk mitigation through optimal seedbed conditions and context-specific evaluations of supplementary biological inoculation.