Abstract:

To explore the effect of controlled water depth on weed control of soil-applied herbicides and its impact on tillering during the seedling stage of hybrid rice cultivar ‘Yongyou 1540’, this study used ‘Yongyou 1540’ as the test rice, 30% butachlor-propargyl emulsion as the test agent, and conducted greenhouse and field experiments. In both experiments, the treatments were arranged with controlled water depths (1-9 cm) and with or without herbicide application to investigate changes in weed occurrence, rice tillering, and herbicide efficacy between 16-31 days after weed sowing under greenhouse conditions and after rice transplanting under field conditions. The greenhouse experiment showed that the deeper the water depth, the lower the weed occurrence, but there was no significant reduction when the water depth exceeded 5 cm. The field experiment showed that as the water depth increased, tiller numbers first increased and then decreased; the maximum tiller number appeared at the water depth of 5 cm. Under herbicide application, weed occurrence continued to decrease from 16-21 days after transplanting as water depth increased. At 26 to 31 days, the occurrence was the smallest at a water control depth of 5 cm, and increased with the increase or decrease of water depth. Without herbicide application, weed occurrence decreased as water depth increased. Moreover, herbicide efficacy was highest at the water depth of 5 cm, and decreased when water depth increased or decreased. This study clearly demonstrated that using controlled water depth at 5 cm with soil-applied herbicide can maximize the combined effect of controlling weed occurrence, weed eradication, and improving the tillering of ‘Yongyou 1540’. These results provide theoretical support for water management in ‘Yongyou 1540’ rice varieties.

Key words: rice, water depth, tillering, occurrence of weeds, weeding effect