Document Type : Research Article
Authors
1
Assistant professor, Rice Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran
2
Professor, Rice Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran
Abstract
Introduction
Rice rationing is one of the ways to increase rice production without expanding the cultivation area. Currently, the average ratoon rice production per unit area is very low, and one of the most important reasons is the decrease in yield due to the lack of control or improper control of weeds. Weed control in ratoon rice is difficult for various reasons such as lack of water and big weed seedlings after harvesting the main crop of rice. In rice ratooning, unlike the main rice cultivation, in which several methods such as puddling, flooding, manual weeding and herbicides are used to manage weeds, the control of weeds is limited to foliar herbicides. Currently, there is not much information about ratoon rice weed control, therefore, investigating the efficiency of different herbicides in this field can lead to the introduction of high-efficiency herbicides in controlling weeds and thus improving the yield of ratoon rice per unit area.
Materials and Methods
This research was carried out during the 2017 and 2018 crop seasons in the research fields of Rice Research Institute of Iran in Gilan and Mazandaran provinces. The studied herbicide treatments were; Doses of 25, 38, 50, and 63 g/ha, a.i of bispyribac sodium SC 10% (Chif), doses of 31, 47, and 63 g/ha, a.i of bispyribac sodium SC 12.5% (Vejin), 40 g/ha, a.i of bispyribac sodium SC 40% (Clean-weed), 25 g/ha, a.i of bispyribac sodium SC 10% (Nomini), 1398 g/ha, a.i of propanil + benzosulfuronmethyl DF 46.6% (Stamdox), 1150 g/ha, a.i of bentazon + MTHPA SL 46% (Bazagran), 45 g/ha, a.i of Triaphamon + Ethoxysulfuron WG 30% (Council) and weedy control. The rice cultivar used in the main cultivation in both locations was Hashemi. The main rice seedlings were transplanted in 20 x 20 cm planting distance. Visual assessment of weeds control and weed biomass measurement were done in two stages. The evaluation of phytotoxicity and growth disorders of herbicides on rice plant and the effectiveness of them in weed control was carried out based on the European standard system.
Results and Discussion
The results showed that bispyribac sodium herbicide, up to 63 g/ha, a.i, did not lead to visible phytotoxicity symptoms in ratoon rice. In Gilan province, Four weeks after herbicide application, the biomass of barnyardgrass (Echinochloa crus galli) in the weedy check was 35 g/m2. The range of barnyardgrass biomass varied from 19 g/m2 for Stamdax to 32 g/m2 for Bazagaran herbicide. Six weeks after spraying, Vejin herbicide (47 and 63 g/ha, a.i), Clean-weed and Nomini had the lowest amount of barnyardgrass biomass with 26, 20, 23 and 26 g/m2, respectively. Which were 71, 78, 75 and 71 percent reduction compared to the weedy check (91 g/m2). The highest efficiency in the sedge (Schoenoplectus maritimus) control was also recorded in the same four treatments. Four weeks after herbicide application, weedy check had the highest weed biomass per unit area with 53 g, although it did not have a significant difference with Stamdax, Clean-weed, Nomini and Vejin herbicide recommended dose. Bazagaran and Council had the lowest amount of sedge biomass with 30 and 32 g/m2, respectively. Sedge biomass reached 150 g/m2 six weeks after herbicide application in the weedy check. Twice the recommended dose of Vejin herbicide with 21 g/m2 had the highest efficiency (86%) in sedge control compared to the weedy check. Although there was no significant difference in this respect with the Nomini, Cleanweed and 150% of Vejin herbicide recommended dose. The lowest efficiency with 35 and 37% belonged to Chif and Stamdax herbicide treatments, respectively. The highest paddy yield with 1683 kg/ha was observed in Clean-weed herbicide treatment, which was 237% increase compared to the weedy check control (710 kg/ha). In Mazandaran province, two herbicides, Stamdax and Bazagaran, were the most effective in reducing weed biomass with 90% and 87%, respectively. This was while the highest paddy yield was observed in Clean-weed and Nomini herbicide treatments (2180 and 2210 k kg/ha, respectively).
Conclusion
This study demonstrated that bispyribac-sodium herbicide effectively controlled weeds in rice ratooning without causing any visible signs of phytotoxicity to the rice plants. This positive outcome led to a significant increase in grain yield. Among the different formulations of this herbicide, Nomini (25 g/ha, a.i) and Cleanweed (40 g/ha, a.i) had the highest efficiency in weed control and as a result, increasing the paddy yield. Therefore, bispyribac sodium herbicide can be used as a suitable replacement for current herbicides in rice ratooning.
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