Effect of integrated weed management on direct seeded rice (Oryza sativa L.)

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Date
2019-02-02
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Department of Agronomy, BAU, Sabour
Abstract
A field experiment was carried out during Kharif season 2016 and 2017 at Bihar Agricultural College farm, Sabour under the Bihar Agricultural University, Sabour, Bhagalpur to assess the effect of integrated weed management on direct seeded rice (Oryza sativa L.). The soil texture of the experimental site was silt loam and was low in available nitrogen (188.61 kg ha-1), and medium in available phosphorus (21.65 kg ha-1) and potassium (194.88 kg ha-1). The experiment was conducted in a randomized block design with fourteen weed management treatments involving various herbicides (Pendimethalin 1000 g a.i. ha-1 (PE), Pendimethalin 500 g a.i ha-1 (PE) fb 1 HW 40 DAS, Almix 4 g ha-1 (PoE), Almix 2 g a.i ha-1 (PoE) fb 1 HW 40 DAS, Ethoxysulfuron 15 g a.i ha-1 (PoE), Ethoxysulfuron 7.5 g a.i ha-1 (PoE) fb 1 HW 40 DAS, Pyrazosulfuran 25 g a.i ha-1 (PE), Pyrazosulfuran 12.5 g a.i ha-1 (PE) fb 1 HW 40 DAS, Bispyribac-Na 30 g a.i ha-1 (PoE) , Bispyribac-Na 15 g a.i ha-1 fb 1 HW 40 DAS (PoE), Azimsulfuron 35 g a.i ha-1 (PoE), Azimsulfuron 17.5 g a.i ha-1 fb 1 HW 40 DAS (PoE), weedy and weed free with three replications. The crop was infested with divergent type of weed flora e.g. sedges, grassy and broad leaved weeds group. However, dominancy of Cyperus rotundus, Echinochloa colona, Echinochloa crusgalli, Cynodon dactylon , Caesulia axillaries and Commellina benghalensis, Eclipta alba, Euphorbia hirta and Phyllanthus niruri were very less, so they were grouped as other weeds. Sedges and broad leaved weeds e.g. Cyperus rotundus, Cyperus iria and Cyperus difformis were controlled very effectively by the Ethoxysulfuron and Azimsulfuron as post-emergence and however, Sedges, Grassy weeds and Broad leaved weeds e.g. Cyperus rotundus, Cyperus iria and Cyperus difformis , Echinochloa colona, Echinochloa crusgalli Caesulia axillaries were controlled very effectively by the Bispyribac-Na as post-emergence. Only Grassy weeds Echinochloa colona, Echinochloa crusgalli were controlled very effectively by Pendimethalin as pre-emergence. At 30 days after sowing, Bispyribac-Na 30 g a.i. ha-1 (T9) and Azimsulfuron 35 g a.i. ha-1(T11) applied as post-emergence being at par, recorded significantly lower density (21.85 and 35.10 m-2) and dry weight (18.02 and 29.42 g m-2) of weeds over rest of the treatments. At 60 and 90 days after sowing, Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) and Azimsulfuron 17.5 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T12) each applied as post-emergence with hand weeding at 40 days after sowing being at par, recorded significantly lower population (24.94, 29.72 and 18.91, 22.55 m-2) and dry weight (38.79, 46.24 and 29.12 , 34.72 g m-2) of weeds over the rest of the treatments. While, application of Pendimethalin 1000 g a.i. ha-1 (T1) and Pyrazosulfuron 25 g a.i. ha-1 (T7) recorded maximum weed population and dry weight which was at par with each other. The maximum weed control efficiency was recorded (88.14%) under Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) and (85.82%) under Azimsulfuron 17.5 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T12). Among herbicides, minimum weed index (1.91%) was recorded under Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) and (6.99%) under Azimsulfuron 17.5 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T12). Whereas, maximum weed index (40.79%) was recorded under Pendimethalin 1000 g a.i. ha-1(T1) and (34.37%) under Pyrazosulfuran 25 g a.i. ha-1 (T7). Among weed management practices, maximum growth attributes, yield attributes and N, P and K uptake by grain and straw were recorded under Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) followed by Azimsulfuron 17.5 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T12) which was comparable to weed free, but was significantly superior over rest of the treatments. Application of Pendimethalin 1000 g a.i. ha-1(T1) followed by Pyrazosulfuran 25 g a.i. ha-1 (T7) was least effective and recorded minimum number of tillers, dry matter accumulation, number of panicles m-2, panicle length, number of grains panicle-1, grain and straw yield as compared to other treatments. However, all the herbicidal treatments were found significantly superior over weedy in respect of crop growth, yield attributes, grain and straw yield and N, P, K uptake by grain and straw. In weed management treatments, higher value of net return (Rs. 85728 and Rs. 79565) and benefit: cost ratio (Rs. 2.67 and Rs. 2.49) was obtained in Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) and Azimsulfuron 17.5 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T12), respectively. While weedy (T14) gave the lowest net return (Rs. 28753).and benefit: cost ratio (Rs.0.99). On the basis of pooled data of the experiment during kharif 2016 and 2017, it may be concluded that post-emergence application of Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) proved superior over rest of the treatments with respect to weed control efficiency, grain yield and economics of direct seeded rice followed by post-emergence application of Azimsulfuron 17.5 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T12). On the basis of conclusion, it may be recommended that post-emergence application of Bispyribac-Na 15 g a.i. ha-1 fb one hand weeding at 40 days after sowing (T10) in direct seeded rice should be practiced for minimizing weed growth and maximizing economic, yield and net return.
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