INFLUENCE OF SWEET SORGHUM STAND DENSITY ON BIOMETRIC INDICATORS UNDER THE CONDITIONS OF THE SOUTHERN FOREST-STEPPE ZONE OF UKRAINE

Abstract

The aim of this study was to determine the impact of plant stand density on the formation of biometric parameters of sweet sorghum in the Southern Forest-Steppe zone of Ukraine, taking into account varietal characteristics, seeding rates, and foliar fertilization options. Special attention was paid to identifying optimal agrotechnical parameters that contribute to the formation of maximum plant density at the full maturity stage, which is a critically important factor in yield improvement. Field research was conducted during 2023–2025 in the Poltava and Vinnytsia regions. A multifactorial experiment with a 4 × 4 × 4 design and four replications was implemented, involving the following factors: variety (4 options), seeding rate (70, 100, 130, and 160 thousand seeds/ha), and foliar fertilization treatments (control, biopreparation, micronutrient fertilizer, and combination). The study employed the DSTU 7169:2010 methodology, the BBCH scale for phenological analysis, and software tools such as Excel and Agrostat for statistical data processing. It was established that stand density at full maturity was significantly influenced by weather conditions, seeding rate, variety, and the applied foliar treatment. Under more favorable conditions in the Vinnytsia region, plant density remained consistently higher than in Poltava. The variety Medovyi provided the highest plant density (up to 140 thousand plants/ha with a seeding rate of 160 thousand and combined fertilization). In contrast, Sylo 700 D showed a lower ability to maintain stand density. The use of biopreparations and micronutrient fertilizers increased plant density by 5–9 % compared to the control. In the Poltava region, higher plant losses were associated with wind erosion and moisture deficiency. Varietal characteristics significantly influenced plant survival: Medovyi and Troistyi demonstrated the highest density stability under different conditions. To achieve optimal stand density of sweet sorghum, both agroclimatic conditions and varietal features must be considered. The most effective varieties are those with high germination energy and resistance to stress factors, particularly Medovyi and Troistyi. An optimal seeding rate for most varieties ranges from 130 to 160 thousand seeds/ha in combination with foliar fertilization. The results confirm the relevance of region-specific agrotechnological approaches in cultivating sweet sorghum for stable dense crop formation and increased yield.