Variation in Soybean Plant Height in Relation to Sowing Time and Plant Density

Abstract

Soybean is a crop of great importance for the economic, ecological and agronomic advantages it provides. In the context of climate change, soybean crop presents certain performance risks in non-irrigated systems, as a result of water and thermal stress. The present study evaluated the development of soybean plants based on the plant height parameter (PH, cm) in relation to sowing date and plant density. The study and field experiments were carried out within ARDS Lovrin. The soybean crop was sown in three different periods: E I (17.04.2025), E II (28.04.2025), E III (12.05.2025). Within each sowing time, five density variants were tested: 45, 55, and 65 plants m⁻² with 25-cm row spacing (V1–V3), and 45 plants m⁻² with 60-cm and 80-cm row spacing (V4–V5). 15 experimental variants resulted, in three replications. Mann-Kendall Test indicated an increasing trend in the mean values ​​of the PH parameter, p<0.001. ANOVA test (p<0.001) and Kruskal-Wallis test (p = 0.0019) indicated significant differences between the mean and median values. Dunn's Post Hoc test generated 105 comparative analyses between the experimental variants and resulted in 69 statistically significant differences, including five cases at the p<0.05 level (*), eight cases at the p<0.01 level (**), and 56 cases at the p<0.001 level (***). In the multivariate analysis, the principal components (PC1, PC2) explained 96.211% of the total variance and identified the correlation of the variants with the sowing times in relation to the plant height parameter. The cluster analysis grouped the variants based on similarity in relation to the values ​​of the PH parameter (cm), under conditions of Coph.corr. = 0.879. The recorded results present scientific and practical importance, with utility for agricultural practice in optimizing technology in soybean cultivation.