Biology and Phenology of Fimbristylis miliacea (L.) in Wet Direct Seeded Rice under Humid Tropical Conditions

Abstract

Background: Weed infestation is a major limitation in wet direct-seeded rice systems, and changes in cultivation practices have increased the dominance of sedge weeds. Fimbristylis miliacea has become a serious weed due to its rapid growth, early maturity, and high seed production, making its control difficult. Understanding its biology and phenology is important for developing effective management strategies. Aims: To study the phenology, growth, floral biology, seed characteristics, and propagation behaviour of F. miliacea under wet direct-seeded rice conditions. Study Design: Field experiment under wet direct-seeded rice ecosystem. Place and Duration of Study: Farmer’s field at Moncompu, Alappuzha district, Kerala, India during kharif 2023 (August–December 2023). Methodology: Ten randomly selected plants of F. miliacea from weedy check plots were tagged and observed from germination to maturity. Phenological stages, growth parameters, floral traits, and seed characters were recorded and statistically analysed using mean, standard deviation, and standard error. Results: Fimbristylis miliacea completed its life cycle within 76–95 days under humid tropical conditions. Germination occurred within 3–7 days and flowering within 25–32 days. The weed attained a mean height of 82.41 cm and produced an average of 6.2 tillers per plant. High reproductive potential was observed with 91.3 spikelets per inflorescence and 28,394 seeds per plant. The weed produced minute lightweight seeds (0.0332 g per 1000 seeds), which were shed along with glumes after maturity, contributing to persistent soil seed banks and effective dispersal. Conclusion: Rapid growth, early maturity, prolific seed production, and efficient seed dispersal enable F. miliacea to persist and dominate wet direct-seeded rice ecosystems. Timely integrated management strategies targeting early growth and reproductive stages are essential for effective control.