|Anders, Merle -|
Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Proceedings
Publication Acceptance Date: January 25, 2010
Publication Date: January 25, 2010
Citation: Gealy, D.R., Anders, M.M. 2010. Performance of weed-suppressive rice cultivars in upland and flooded production systems in Arkansas [abstract]. Proceedings of Southern Weed Science Society. 63:112. Technical Abstract: Asian indica rice lines such as PI 312777 can suppress barnyardgrass (Echinochloa crus-galli) effectively in traditional drill-seeded, flood-irrigated (FLI) production systems, but their weed suppression potential in upland (furrow irrigation; FUI) production systems is unknown. FUI systems are gaining popularity because of their potential for water savings and their suitability for improved productivity on steeply sloped fields. Thus, weed-suppression potential of selected indica and commercial tropical japonica rice cultivars was compared under FLI and FUI production systems and three weed management levels. Following preparatory tillage in late May, 2009, plots to be managed under FUI were bedded using a modified Brandt FR-21. Rice was then planted 1.9 cm deep into 10 rows spaced 19 cm apart using an Almaco HDGD10R drill. FUI plots had alternating deep furrow and raised bed sections (2 rows furrow-2 rows raised-2 rows furrow-2 rows raised-2 rows furrow). Barnyardgrass seed was broadcast uniformly at planting. Weed suppression by PI 312777 and Rondo (indicas), and Lemont, Wells, Bengal, and CL 171AR (commercial cultivars), was evaluated under ‘low’, ‘medium’, and ‘high’ weed management levels (LWM, MWM, and HWM, respectively). Plots were flush-irrigated as necessary after emergence to maintain healthy rice plants. FLI plots were flushed by adding water until soil surfaces were completely submerged, and were drained after ~20 h. FUI plots were flushed by adding water until such time that soil on top of the beds became saturated. Prior to establishment of permanent flood on FLI plots on June 30, 110 kg/ha nitrogen was applied to FLI and FUI plots as urea and Agrotain-treated urea, respectively. FUI plots were flushed after N application and seven additional times during the crop season—a low frequency due to excessive natural rainfall. Based on anticipated weed pressure, HWM and MWM plots were sprayed pre-emergence with 0.44 kg/ha clomazone, and LWM plots were sprayed post-emergence with 1.1 kg/ha propanil. The FUI, HWM plots were also sprayed post-emergence with 0.36 kg/ha quinclorac + 0.55 kg/ha bentazon + 0.28 kg/ha aciflourfen + 1% oil. The experimental design was a split, split plot, with irrigation methods as main plots, cultivars as sub plots, weed management levels as sub sub plots, and four replications. Averaged over cultivars and management levels, FLI yields were about 3 times higher and weed biomass production about half of that for FUI. Yield losses in FUI plots may have been worsened by delayed initial emergence and growth, and the substantial clomazone injury to rice that sometimes occurred in deep furrows. Broadleaf weeds were absent from FLI plots, but represented about 10% of the weed biomass in FUI plots, particularly under MWM, where herbicides controlled competing grass weeds. Weed control and yields were greatest under HWM and lowest under LWM. HWM and MWM frequently produced similar results, particularly in FLI plots where the combination of crop competition and moderate herbicide inputs reduced weed growth greatly for most cultivars. Overall, weed control and yields were greatest for PI 312777 and least for Lemont, while other cultivars were intermediate. Total weed biomass in PI 312777 was only 14%, 26%, and 33% of that in Lemont, Wells, and Rondo, respectively. From these initial results, it is clear that weeds can be a major challenge in FUI systems, and that weed suppression potential of the rice cultivar can strongly influence crop productivity. PI 312777 performed better than commercial tropical japonica cultivars under FUI, suggesting that improved indicas may prove to be useful in these systems.