Growth and morphological response of imazamox-tolerant sorghum (Sorghum bicolor L.) to increasing herbicide doses under field conditions

Sorghum is characterized by high adaptability to abiotic stress; however, its early growth and morphological development may be influenced by herbicide application, even in tolerant hybrids. The present study aimed to evaluate the growth dynamics and morphological response of the imazamox-tolerant sorghum hybrid Sentinel IG to increasing doses of the herbicide Pulsar 40 (imazamox). A three-year field experiment was conducted under rainfed conditions in South Central Bulgaria during the period 2023–2025. Plant height was measured at key phenological stages (4–5 leaf stage, before heading, and at final maturity) to assess the impact of herbicide dose and environmental variability on crop growth. The results demonstrated a consistent dose-dependent reduction in plant height, particularly at the pre-heading and final growth stages. The highest herbicide dose (480 ml da⁻¹) resulted in persistent growth suppression across all experimental years. Interannual differences were observed, reflecting the influence of climatic conditions on growth expression. The study confirms that excessive herbicide doses negatively affect sorghum growth dynamics, even in tolerant hybrids, highlighting the importance of dose optimization for sustainable crop management.