Integrated use of the stale seedbed technique with preemergence herbicides to control weedy rice in wet seeded rice

Abstract

This study was undertaken to investigate the integration effects of pretilachlor, oxadiazon, and dimethenamid with or without glyphosate in stale seedbed method to control weedy rice in wet seeded rice. The study, conducted in 2018 and 2019, comprised two seedbed treatments in main plots: with and without glyphosate (850 g ae ha−1), and four sub plot treatments: pretilachlor, oxadiazon, dimethenamid, and unsprayed check. Fifteen days after glyphosate spray, each sub plot was treated with preemergence herbicides at 500 g ai ha−1, respectively under standing water condition (2 to 3 inches) and the water level was maintained for 7 days. Pre-germinated rice seeds (var. MR297) were hand broadcasted in the moist soil at 120 kg ha−1 of seeding rate. In 2019, the density and dry weight of weedy rice were 30 and 118% higher than those observed in 2018. Stale seedbed with glyphosate reduced weedy rice dry weight 12% as compared to those observed in stale seedbed without glyphosate. Addition of oxadiazon and pretilachlor in stale seedbed drastically reduced weedy rice dry weight by 70 to 88% and 53 to 60%, in both years. Dimethenamid contributed significant reduction of weedy rice dry weight by 19% in 2019 only but failed to provide a positive economic return. Integration of pretilachlor and oxadiazon in stale seedbed with glyphosate gave profitable returns $84 to 311.4 ha−1 and $175.7 to 483.8 ha−1, respectively. Without the presence of glyphosate, pretilachlor or oxadiazon contributed a positive return $318.9 or $469.4, respectively, in 2018, but the economic returns were negative in 2019. These results suggest that integration of pretilachlor or oxadiazon in stale seedbed with glyphosate is more crucial when the weedy rice infestation is high, but glyphosate can be excluded from the management regime when the weedy rice populations are low.

Utilizing germinability thresholds for optimizing stale seedbed applications to control red rice (Oryza spp.) in California rice cropping systems

“…The foundational goal of this technique is to germinate as many weed seeds as possible from the seedbank and eliminate them with nonselective preplant control strategies. This method is implemented in rice by flooding the field to some degree for some amount of time (Ceseski et al 2022; Dilipkumar et al 2022; Singh et al 2018). Flooding ceases after weed seeds germinate and seedlings emerge.…”