Environmental Influences on Seed Germination and Seedling Emergence in Four <i>Echinochloa</i> Taxa

<i>Echinochloa</i> species are troublesome weeds that cause serious problems in paddy fields. Due to the fact that the genus <i>Echinochloa</i> comprises numerous species and subspecies, research on its seed germination and emergence ecology is still insufficient. In this study, the influence of varying temperatures; light, osmotic, and saline conditions; and depth of seed burial on the germination of <i>Echinochloa</i> seeds and the emergence of seedlings was determined through laboratory and pot tests: <i>E. crus-galli</i> var. <i>crus-galli</i>, <i>E. crus-galli</i> var. <i>mitis</i>, <i>E. crus-galli</i> var. <i>praticola</i>, and <i>E. caudata</i>. Seed germination of the constant temperatures in the four <i>Echinochloa</i> taxa was examined between 15 and 40 °C, and optimum germination occurred over the following temperature ranges: 25–35 °C for <i>E. crus-galli</i> var. <i>crus-galli</i>; 15–25 °C for <i>E. crus-galli</i> var. <i>mitis</i>; 15–40 °C for <i>E. crus-galli</i> var. <i>praticola</i>; and 15–35 °C for <i>E. caudata</i>. Fluctuating temperatures were conducive to seed germination in all four <i>Echinochloa</i> taxa. Except for <i>E. crus-galli</i> var. <i>crus-galli</i> and <i>E. crus-galli</i> var. <i>mitis</i> exposed to very acidic conditions (pH = 4), germination of seedlings from the four taxa of <i>Echinochloa</i> was not evidently affected by pH or light. Seed germination of the four <i>Echinochloa</i> taxa decreased as water stress decreased (<−0.2 MPa); however, it occurred across a wide spectrum of salt concentrations (0–320 mM NaCl). The seeds that were placed 0–0.5 cm below the surface had the highest rate of seedling emergence, which declined gradually as burial depth increased. This result demonstrates that deep tillage is an efficient management method for decreasing the seedling emergence of various weed species. This study’s findings will enhance our comprehension of the conditions necessary for the germination and emergence of <i>Echinochloa</i> seeds, as well as furnish information that may assist in managing its growth.