Germination ecology of Chinese sprangletop (Leptochloa chinensis) in the Philippines

Chinese sprangletop is a grass weed that has the ability to grow in both flooded and upland conditions, which makes it a widespread and abundant weed in rice and many other crops. Experiments were conducted to study the germination of this weed in the Philippines. Germination was strongly stimulated by light and warm fluctuating temperatures, suggesting high emergence of Chinese sprangletop on bare ground such as a crop seedbed. A high level of germination (95%) immediately after seed harvest suggests that the soil seed bank of this species could be depleted by stale-seedbed strategies. Seed burial depth in soil strongly influenced emergence of this weed, and no seedlings emerged from seeds buried at depths of ≥ 0.5 cm. Maximum emergence (80%) from seeds placed on the soil surface suggests that no-till practices would enhance the emergence of seedlings. Seedling emergence from surface-sown seeds was similar (80 to 82%) between saturated and aerobic-moist soil, demonstrating that this weed does not require a saturated soil and that it can emerge from a moist soil. Flooding, even though not continuous or deep, had a suppressive effect on the emergence and dry matter of Chinese sprangletop. Germination responses to light and seed burial depth were different between our study in the Philippines and the study conducted with seeds of an Italian population, suggesting that Chinese sprangletop might be polymorphic. The implications of this information for weed management strategies are discussed