Chemical control of weedy rice in precise hill‐direct‐seeded rice in South China

Abstract

Precise hill‐direct‐seeded rice, which is both cost‐ and labor‐saving, is based on the direct seeding of rice by using a precision rice hill‐drop drilling machine. Weedy rice (Oryza sativa f. spontanea), also known as “red rice”, is a major weed in precise hill‐direct‐seeded rice, causing an ≤80% yield loss and a reduction in grain quality. The aim of this study was to evaluate the control efficiency of weedy rice by pretilachlor (a pre‐emergence herbicide) and fenclorim (a safener) and their safety for precise hill‐direct‐seeded rice in two consecutive years. The amount of rice seed germination was accelerated by soaking the seeds in the safener at 0.67 g ai L−1 for 1 h before sowing. The pre‐emergence pretilachlor treatments were applied 2 days after sowing cultured rice. The inhibition of the shoot fresh weight of the cultured rice was reduced by 3.3, 6.4 and 7.4% with 450, 900 and 1350 g ai ha−1 of pretilachlor at 32 days after sowing (DAS) and that of the root fresh weight was reduced by 2.6, 4.9 and 8.1%, respectively. With fenclorim and pretilachlor in a precise hill‐direct‐seeded rice field in 2010 and 2011, the weedy rice control efficiency at 32 DAS was reduced by 100 and 98.0%, respectively. The pre‐emergence pretilachlor treatments that were applied at 2 DAS were much more efficient in the weedy rice control and less inhibitory to the cultured rice growth. The rice yield was increased by 26.1–26.7% in the mechanical precise hill‐direct‐seeded rice, relative to the manual‐seeding rice, with the application of fenclorim and pretilachlor.

Effect of Pretilachlor on Weedy Rice and Other Weeds in Wet-Seeded Rice Cultivation in South Vietnam

“…Safeners are used to enhance herbicide tolerance in selected monocot crops without affecting herbicidal susceptibility of the target weed species (Davies and Caseley, 1999;Shen et al, 2013). In a recent study in China, the pretilachlor herbicide applied at 1350 g ha -1 reduced rice fresh weight by only 7% (Shen et al, 2013). However, in our study, the maximum rate of pretilachlor was only 900 g ha -1…”

“…As the pretilachlor used in our study had a safener in it, no phytotoxic effects were observed. Safeners are used to enhance herbicide tolerance in selected monocot crops without affecting herbicidal susceptibility of the target weed species (Davies and Caseley, 1999;Shen et al, 2013). In a recent study in China, the pretilachlor herbicide applied at 1350 g ha -1 reduced rice fresh weight by only 7% (Shen et al, 2013).…”

“…Because of the physical and physiological similarities of weedy rice to cultivated rice, it is difficult to control weedy rice in conventional rice cultivars. Recently, it was found that the herbicide pretilachlor (with a safener) has the potential to reduce weedy rice infestation in wet-seeded rice systems (Shen et al, 2013). Pretilachlor is a selective systemic herbicide and it is absorbed by the germinated shoots and roots.…”

Estimation of weed dry biomass and grain yield as a function of growth and yield traits under allelopathic weed management in maize

“…The exact mechanism of action of most plants aqueous extracts is still unclear but many reports have mentioned phytotoxicity of used plant combinations in their individual capacity. A possible mechanism may involve a decreased activity of some enzymes like proteases, ureases and phosphorelases, a decline in chlorophyll content and photosynthesis, a greater cell membrane permeability and lipid metabolism (Shen et al, 2013).…”

“…Consequently, favoring crop growth indices like leaf area index, leaf area duration, dry matter accumulation and crop growth rate through lessening the competition for available resources and improving yield components in maize, cob length, number of grains per cob, 1000 grain weight thus, resulted in higher stalk, and economic and biological yield (Catherine et al, 2003;Shen et al, 2013).…”