Document Type : Complete scientific research article
Authors
1
Ph.D Student, Department of Agronomy, Gorgan University of Agricultural Sciences and Natural Resources
2
Professor, Department of Agronomy, Gorgan University of Agricultural Sciences and Natural Resources
3
Associate Professor, Faculty member, Rice Research Institute of Iran, Mazandaran Branch, Agricultural Research, Education and Extension Organization (AREEO), Amol, Iran
4
Associate Professor, Department of Agronomy, Gorgan University of Agricultural Sciences and Natural Resources
10.22069/ejcp.2026.21591.2595
Abstract
Background and objectives: Rice is one of the most important cereals and the main food of more than half of the world's population. Changing the farming method from submerged to aerobic cultivation using aerobic rice genotypes plays an important role in maintaining and sustaining rice production. On the other hand, weed management is one of the main challenges in this planting system. Therefore, the use of suitable varieties, optimal planting distance and application of the correct doses of herbicides are of great importance in the aerobic cultivation system. thus, the present study was conducted with the aim of investigating the possibility of reducing the dose of pendimethalin herbicide with different planting intervals on weed population control and its impacts on yield components and grain yield of two aerobic Vandana and high-yielding Neda rice varieties under aerobic cultivation conditions.
Materials and methods: The experiment was carried out as a split-block in a randomized complete block design with three replications in the Rice Research Institute of Iran (Mazandaran-Amol) during 2020-2021 and 2021-2022 growing season. Experimental treatments were the rice varieties at two levels (Vandana (aerobic genotype) and Neda (high-yielding and drought-tolerant rice)) as the main factor, sowing row spacing at three levels (12.5, 25 and 37.5 cm) as the sub-factor and herbicide treatment at five levels (control (without weed control), pendimethalin (1 L ha-1) + bispyribac sodium, pendimethalin (2 L ha-1) + bispyribac sodium, pendimethalin (3 L ha-1) + bispyribac sodium and weeding) as the sub-sub factor were considered. The bispyribac sodium was used at the dose of 100 cc ha-1 in all experimental plots.
Results: The results indicated that the number of filled grains per panicle and the ability to compete with weeds of the aerobic variety Vandana were higher compared with the high-yielding variety Neda. The highest plant height (85.46 cm) and panicle length (18.71 cm) were observed at a sowing space of 12.5 cm, while the plant height and panicle length significantly reduced when the sowing space increased. Also, the highest number of panicles m-2 (292.26 panicles m-2) was obtained at the sowing row spacing of 12.5 cm, while increasing the sowing row spacing to 25 and 37.5 cm, the number of panicles m-2 reduced by 8.2% and 19.6 %, respectively. The weeding treatment led to highest plant height, panicle length, number of panicles (m-2), number of filled grains per panicle and grain yield, and the treatment of pendimethalin (3 L ha-1) + bispyribac sodium ranked next. In addition, the use of pendimethalin (2 L ha-1) + bispyribac sodium produced the highest 1000-grain weight (25.94 g). Although the highest grain yield was achieved in weeding conditions (7323.9 kg ha-1), but the application of pendimethalin (3 L ha-1) + bispyribac sodium significantly led to the control of weeds and improvement of yield components and grain yield compared with the use of pendimethalin (1 L ha-1) + bispyribac sodium, pendimethalin (2 L ha-1) + bispyribac sodium and control conditions.
Conclusion: According to the results of the present study, in the aerobic cultivation conditions, the use of Vandana variety, the sowing row spacing of 12.5 cm and the application of pendimethalin (3 L ha-1) + bispyribac sodium had the greatest impact in reducing the dry weight accumulation of weeds and improving rice grain yield.
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