Emergence of red rice (Oryza sativa) ecotypes under dry-seeded rice (Oryzasativa) culture

The effect of seeding depth on emergence of red rice (Oryza sativa) ecotype s from Arkansas (AR), Louisiana (LA), and Mississippi (MS) was determined u nder dry-seeded rice production in clay and silt loam soils in Arkansas. By 21 d after planting (DAP), all red rice ecotypes had emerged from planting depths of 1.3, 2.5, 5.0, and 7.5 cm in both clay and silt loam soils. In s ilt loam soil, seedling emergence from 2.5 cm 7 DAP tended to be greater th an from 1.3 cm in an early (normal temperature) planting. Also in this situ ation, the LA ecotype emerged more vigorously than the other ecotypes at al l seeding depths and emerged from 7.5 cm at levels 1.5 times those of the o ther ecotypes at the same depth. In the clay soil, seedling emergence from 7.5 cm at 21 DAP was greater for the LA and MS ecotypes than for the AR eco type in an early planting, but these differences were not observed for a la te (elevated temperature) planting. Seedling emergence was earlier and grea ter in silt loam than in clay. The LA ecotype generally produced the greate st aboveground dry matter, especially at the early planting. The MS ecotype averaged 30% less dry matter production than the AR ecotype for the late p lanting in both soils. The ability of the LA and MS ecotypes to emerge from greater depths than the AR ecotype under certain soil and temperature cond itions suggests that they could be more difficult to control with cultural practices used in dry-seeded rice culture.