The stale-drill establishment method for rice: Weed community, rice stand development, and yield components of two vigorous japonica cultivars

Abstract

Rice grown in the Sacramento Valley of California is predominantly water seeded (WS), by direct-seeding rice into flooded basins. The effects of flooded rice monoculture and limited herbicides have led to difficult-to-control weed populations, and widespread local herbicide resistance. A novel “stale-drill” rice establishment method has been under investigation in California, to address these constraints. Two rice varieties with high seedling vigor (‘M-206’, ‘M-209’) were dry-drilled to 3 cm and 6 cm in 2018 and 2019, and fields were flush-irrigated to initiate weed germination prior to stand emergence. A postplant-burndown (PPB) application of glyphosate at 870 g a.e. ha-1 was applied 6-7 days after planting (DAP), at rice emergence, which controlled >50% of total seasonal weeds. Glyphosate PPB caused rice first-leaf dieback, but no other symptoms developed. Planting depth or cultivar did not affect date of emergence either year. Deeper seeding reduced M-206 and M-209 stands by 15.4% and 5.2%, respectively, in 2018, but not in 2019. Increased tillering compensated for stand reductions in 2018. Panicle yield components were largely unaffected by planting depth in 2018, however florets panicle-1 and filled grains panicle-1 were slightly greater for both cultivars at 6 cm. In 2019, M-209 suffered reductions in florets per panicle and grain filling at 6 cm planting depth. Grain yields were unaffected by planting depth in either study year. M-206 and M-209 grain yields were 10.2 T ha-1 and 12.2 T ha-1 respectively, in 2018, and 9.4 T ha-1 and 9.1 T ha-1 respectively, in 2019. Proper water management and scouting are essential to ensure that PPB treatments do not injure emerging rice to the extent that weak or reduced stands result. However, the present study serves as a promising proof-of-concept for the “stale-drill” method as an alternative stand establishment method in mechanized rice production.