The Responses of Barnyardgrass (Echinochloa crusgalli (L.) Beauv) and Rice Barnyardgrass (Echinochloa oryziodes (Ard) Fisher) to Flooding and Soil Depth

In order to study the effect of water level and soil depth on the germination rates of barnyardgrass and rice barnyardgrass, an investigation was conducted at Rice Research Institute of Iran (Rasht) in 2008. Treatments included weed species (Echinochloa Crus-galli and Echinochloa oryziodes), water level (0, 3, 6 and 9 cm) and soil depth (0.5, 1.5, 2.5 and 3.5 cm). The experimental design was a Randomized Complete Block Design (RCBD) with three replications in factorial arrangement. Experiment were laid out in covered outdoor conditions. Results showed that water level and soil depth affected germination rate, seedling mortality, seedling germination, height, dry matter accumulation and radicle length, significantly. Both water level and soil depth affected barnyardgrass more than rice barnyardgrass. Average germination of seeds in 9 cm of water was 80% and 30% for rice barnyardgrass and barnyardgrass 20 day after sowing, respectively. Also increasing soil depth decreased seed germination significantly. Regression analysis showed that by increasing water level and soil depth, the germination rate of barnyardgrass decreased more than rice barnyardgrass. This study showed that rice barnyardgrass is more tolerant than barnyardgrass to water level or soil depth. These results indicate that rice barnyardgrass has more chance to survive in paddy field of Iran.