|Gibbons, James -|
|Moldenhauer, Karen A -|
Submitted to: Weed Science Society of America Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 8, 2010
Publication Date: February 11, 2010
Citation: Gealy, D.R., Gibbons, J.W., Yan, W., Moldenhauer, K.K. 2010. Effect of early planting on weed suppression activity of indica and commercial U.S. rice cultivars [abstract}. Weed Science Society of America Meeting Proceedings, February 7-11, 2010, Denver, Colorado. Abstract O-265. 2010 CDROM. Technical Abstract: Indica and commercial cultivars can suppress barnyardgrass when drill-seeded into ‘warm’ soils and grown under flood-irrigation in Arkansas. Because early planting is popular with growers and considered to improve productivity and flexibility, weed suppression tests were planted in the field on April 15 and May 20, 2008 to achieve cool and warm early growth conditions, respectively. Barnyardgrass seed was broadcast uniformly at planting. Grass weed suppression performance for 24 rice cultivars was evaluated. Cultivars included weed-suppressive indicas, commercial tropical japonicas and hybrids, and cool season cultivars developed for early planting. The experimental design was a split plot, with cultivars as main plots, weed levels (weed-free or weedy) as sub plots, and four replications. Planting dates were analyzed separately. Weed-free plots were sprayed with commercial herbicides to control grass weeds; weedy plots were sprayed with 1/4X propanil to stunt grasses; and all plots were sprayed with bentazon to kill broadleaf weeds. Weed pressure and the resulting loss in rice yield were lower in the earlier planting. The dominant weed species in the April planting was broadleaf signalgrass and in the May planting was barnyardgrass. Weed suppression was positively correlated with rice emergence rate, and the suppressive indicas and hybrids (e.g. PI 312777 and CL-XL723) provided greater suppression than many tropical japonicas and cool season cultivars. In the April planting, however, PI 312777 and CL-XL729, were less suppressive than the cool season cultivar, Spring, suggesting that early planting may enhance suppression by some cool season cultivars in favorable environments.