Bed Width and Drill Spacing Effect on Weed Management in Furrow-Irrigated Rice.

Furrow-irrigated rice (Oryza sativa L.), or row rice, has increased in acreage in Arkansas in the past few years. This practice allows growers to potentially grow rice on steeper ground that would require a vast number of levees that is labor and time intensive. However, this non-traditional rice growing method has a weed management drawback. The removal of the flood as a means of weed control places additional pressure on other weed management strategies and potentially different herbicide programs. Therefore, the objectives of this research were to determine if the manipulation of drill row spacing and bed width would influence season-long weed control. Two studies were seeded with hybrid rice RT7521 FP in 2021 and 2022 at Lonoke and Pine Tree, Ark. to evaluate treatments that consisted of three bed widths (30-, 38-, and 60-in.) and four drill row spacings (5-, 7.5-, 10-, and 15-in.). Barnyardgrass [Echinochloa crus galli (L.) P. Beauv.] density was assessed at the 5- to 6-leaf rice stage and preharvest. Canopy closure was captured with aerial digital images from a small, unmanned aircraft system (sUAS) collected at the 3-6 leaf and panicle differentiation rice stages. Rough rice yield was harvested with a plot combine and adjusted to 13% moisture. In general, barnyardgrass densities were lower across narrower drill row spacings (=7.5-in.) and bed widths (30-in.) early in the season; however, little differences were seen at the later preharvest timing. Canopy closure responded similarly as narrower drill row spacing and bed width had greater canopy closure. Rough rice yield was impacted less by drill row spacing and bed width, but narrower drill row spacing and bed width had a slightly higher numerical yield increase. Early findings suggest that a grower choosing this method of rice management should choose the narrowest drill row spacing allowed by their equipment and the narrowest bed widths that they can obtain to maximize weed management efforts. [ABSTRACT FROM AUTHOR]