Comparison of Competitive Ability of Cultivated Rice and Weedy Rice with Existing Weeds at Seedling Stage

Abstract

Weeds are the most important biological restraint in rice ecosystems which cause to reduceyield quantitatively and qualitatively. Weedy rice (Oryza sativa L. f. spontanea) is one of themost widespread and problematic weed, cause high yield losses when co-occurs with ricecrop. Weedy rice is taxonomically classified as the same species as cultivated rice (O. sativa),but is strongly characterized by its seed shattering and dormancy, which assist to successfullycompete with rice crop and other weeds.

The competition between crops and weeds is often affected by many factors, includingcultivation methods and type of crop. The control of weedy rice has been difficult due to itsmorphological similarity to cultivated rice. Therefore the possible approach is use of preeminent characters for rice crop improvement in breeding programs. This study was carriedout in an experimental garden to evaluate the weed-crop competition under differentcultivation conditions at seedling stage. Weedy rice and improved rice (variety At 362) wereused under Randomized Complete Block Design (RCBD) with 3 replicates. 14-day old riceseedlings were used for transplanting plots.

The eight patterns of planting methods (T1-Improved rice transplanted with weeds, T2-Improved rice transplanted without weeds, T3-Improved rice direct seeded with weeds, T4-Improved rice direct seeded without weeds, T5-Weedy rice transplanted with weeds, T6-Weedy rice transplanted without weeds, T7-Weedy rice direct seeded with weeds, T8-Weedyrice direct seeded without weeds.) were used as treatments. Plant height and number of tillerswere measured at seedling stage.

The results of ANOVA revealed that the planting pattern, block effect and their interactionwere significantly (p<0.05) affected to both tested characters. The significantly (p<0.05)highest plant height (90.083±12.32501 cm) and tiller number (3.7083±1.428869) wereobserved in T6 (weedy rice transplanted plot without weeds) while lowest plant height (55.88cm) and tiller number (2.083) observed in T3 (improved rice direct seeded plot with weeds).All planting models, Weedy rice showed the higher performances compared to that ofimproved rice and both had poor performances at direct seeded field. The results suggest thatweedy rice perform successfully with infestation of weeds in transplanted fields because ofits enhanced competitive ability.