Germination Ecology and Competitive Ability of Calendula arvensis as a Weed in Winter Cereal Monocultures

Abstract

Seed germination ecology and competitive performance of Calendula arvensis were investigated to understand its persistence and interference potential in winter cereal monoculture systems. Laboratory and field experiments were conducted to evaluate the effects of temperature, moisture availability, light exposure, and burial depth on germination behavior, along with its competitive ability under crop–weed interactions. Results indicated that germination was strongly influenced by cool temperature regimes typical of winter cropping seasons, with optimal germination observed under moderate chilling conditions. Light exposure significantly enhanced germination of surface-sown seeds, while deeper burial reduced emergence due to limited light penetration and altered soil microclimate conditions. Moisture availability played a crucial role in seedling establishment, with higher germination percentages recorded under adequate soil moisture conditions compared with drought-stressed environments. Seed burial studies revealed that shallow soil layers supported maximum emergence, whereas deeper seeds remained viable but dormant, contributing to long-term seedbank persistence. Competitive interaction experiments demonstrated that C. arvensis significantly reduced cereal crop growth parameters, including plant height, tillering, biomass accumulation, and yield components, particularly when weed emergence occurred early in the crop growth cycle. Increased cereal planting density partially suppressed weed growth by enhancing canopy closure and reducing resource availability for weed establishment. Seasonal field observations showed that rainfall events and mild winter temperatures favored synchronized germination and rapid weed emergence. The species exhibited strong adaptive traits, including persistent seedbank formation and efficient resource utilization, enabling successful establishment in monoculture cereal systems.