The optimum seeding rate varies for a hybrid in furrow-irrigated rice

Furrow-irrigated rice (Oryza sativa L.) (FIR) is a common practice in much of the mid-southern United States; however, management practices are often based on research findings in conventional flood rice (CFR). The FIR environment differs significantly from CFR and differs within each individual field, as a flood is typically held in the lower portion of the field while the top of the field remains aerobic. Seeding rate recommendations in FIR are currently extrapolated from CFR data; therefore, a study was initiated in 2022 with XP753 and continued in 2023–2024 with RT7421 FP to define the optimum seeding rate of hybrid rice grown in the FIR system. Five seeding rates from 43 to 215 seeds/m² were tested in a split-plot design, with the whole-plot factor being area within the field and the split-plot factor being seeding rate. Across eight site-years, rice density (plants/m²) was significantly affected by seeding rate. Rice density increased as seeding rate increased. Conversely, the effective stand (number of plants/seed) decreased as seeding rate increased. Approximately 0.79 plants/seed were established with a seeding rate of 43 seeds/m², while 0.53 plants/seed were established when planting 215 seeds/m². There was a significant interaction affecting grain yield between area within the field and seeding rate. In the top end of the field, 215 seeds/m² were required to maximize yield potential, while 129 and 86 seeds/m² were required in the middle and bottom of the field, respectively. Data presented here indicate that variable rate seeding should be considered in the FIR system.