Seed Germination Ecology and Herbicide Sensitivity of Aeschynomene indica L.: Implications for Integrated Management in Paddy Fields

Aeschynomene indica L. has become a problematic weed in the upland direct-seeding rice fields of the lower Yangtze River region, China, leading to substantial yield reductions. A comprehensive understanding of its seed germination ecology and response to herbicides is crucial for developing effective control strategies. This study examined the effects of major environmental factors including temperature, light, pH, salt stress, osmotic potential, and burial depth on seed germination of A. indica and assessed the efficacy of 20 commonly used herbicides in rice under controlled conditions. Results revealed that germination was highly sensitive to temperature, with optimum constant and alternating temperatures of 35 °C and 40/30 °C (day/night), respectively, both achieving germination rates above 90%. The seeds were non-photoblastic, maintaining a high germination rate of 83.33% under complete darkness. Germination remained consistently high across a broad pH range from 4 to 9, with rates ranging from 83.33% to 96.67%. Salt and osmotic stresses markedly suppressed germination, with EC50 values of 195.08 mmol·L−1 NaCl and −0.43 MPa, respectively. Seedling emergence decreased significantly with increasing burial depth, with no emergence occurring at depths greater than 7 cm. The EC50 for emergence was 4.21 cm. Among the herbicides screened, saflufenacil and mesotrione were the most effective pre-emergence treatments, with GR50 values of 5.38 and 12.02 g ai ha−1, respectively. Florpyrauxifen-benzyl and fluroxypyr-meptyl exhibited the highest post-emergence activity, with GR50 values of 0.20 and 19.69 g ai ha−1, respectively. These results underscore the high ecological adaptability of A. indica to paddy fields conditions and provide a scientific foundation for integrating chemical control with cultural practices such as deep tillage into sustainable weed management systems for paddy fields.