Flooding, allelopathic varieties, and non-synthetic herbicides are potential options for weed management in organic rice production. However, little research has been conducted on the effectiveness of these tools for weed management in organic rice production under field conditions. Experiments were conducted from 2016 to 2018 to understand the impact of flooding on the emergence of five major weeds in rice, determine the weed suppressive potential of four potentially allelopathic rice varieties, and evaluate the efficacy of seven non-synthetic herbicides. All weeds but Palmer amaranth emerged at 2.5 cm flooding depth, though the degree of emergence varied across weed species. Weedy rice and barnyardgrass had <10% and <5% emergence, respectively, at 7.5 cm flooding depth. Flooding depth at 2.5 cm delayed the emergence of Amazon sprangletop, Nealley's sprangletop, barnyardgrass, and weedy rice by 8, 13, 8, and 2 days, respectively. With respect to weed suppressive rice varieties, PI 312777 was the best performing weed suppressive variety in the field with a relative yield of 60% and 81% in 2017 and 2018, respectively compared to a weed-free check. Among the non-synthetic herbicides evaluated, Homeplate(R) (caprylic acid + capric acid) showed good levels of weed control, causing 93% and 80% injury to broadleaf signalgrass and barnyardgrass, respectively. Rice injury with Homeplate(R) was substantial (46%) at 14 days after application (DAA), but rice crop recovered from this injury by 21 DAA. Overall, results from this research illustrate that these non-chemical options can be utilized as a part of an integrated weed management program in organic rice production.
