EFFICACY OF HERBICIDE COMBINATIONS FOR WEED MANAGEMENT IN DIRECT SEEDED KHARIF RICE
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Date
2023
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Abstract
A field experiment entitled “Efficacy of herbicide combinations for weed management in direct seeded kharif rice” was carried out in Instructional-cum-Research farm, Assam Agricultural University, Jorhat during kharif, 2022.The Randomized Block Design was used to arrange 12 weed management treatments in 3 replications. The treatments were weed free (T1), weedy check (T2), bispyribac-sodium 25g/ha + pyrazosulfuron 20g/ha 20 days after sowing (DAS) as check (T3), pretilachlor 750g/ha pre-emergence followed by fenoxaprop-p-ethyl 50 g/ha + ethoxysulfuron 15g/ha 20 DAS (T4), pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS (T5), pretilachlor 750g/ha pre-emergence followed by penoxsulam 30 g/ha + bentazone 1080 g/ha 20 DAS (T6), glyphosate 1000 g/ha followed by one mechanical weeding 30 DAS (T7), glyphosate 1000 g/ha followed by fenoxaprop-p-ethly 50g/ha + ethoxysulfuron 15g/ha 20 DAS (T8), glyphosate 1000 g/ha followed by triafamone + ethoxysulfuron 60g/ha at 20 DAS (T9), glyphosate 1000g/ha followed by penoxsulam 30g/ha + bentazone 1080g/ha 20 DAS (T10), hand weeding at 20 DAS and weeding with grubber at 40 DAS (T11) and two mechanical weeding at 20 and 40 DAS (T12). The texture of the soil was sandy loam with pH of 5.5, bulk density of 1.40 Mg/m3, organic carbon of 0.67% and available N, P2O5 and K2O of 289.93, 19.69 and 114.11 kg/ha, respectively.
All treatments significantly lowered the weed density as well as dry matter in terms of broad-leaved, sedge and grassy weeds at 60, 90 and 120 DAS and at harvest as compared to weedy check. Significant reduction (75.59, 56.97, 44.77 and 30.44 %, respectively) in density of total weeds was observed in treatment (T5) pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS at 60, 90 and 120 DAS as well as at harvest over weedy check. The same treatment recorded significantly lower dry matter of total weeds at 60, 90 and 120 DAS and at harvest to the tune of 73.39, 52.71, 37.76 and 27.46 %, respectively over weedy check.
Pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS (T5) showed higher result with regards to crop growth parameters viz., plant height, number of tillers/m2, leaf area index, dry matter accumulation/m2 and crop growth rate at all the stages as compared to rest of weed management treatments except for plant height which was found to be not significant at 30, 120 DAS and at harvest. The above-mentioned treatment also showed higher result in terms of yield attributing characters viz., number of panicles/m2 and number of grains/panicle with 77.60 and 40.97 % increase over weedy check. In case of panicle length and test weight, the result was found to be not significant among all the treatments. Grain yield was found to be significantly higher in pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS (T5) with 175.16 % higher over weedy check and was at par with pretilachlor 750g/ha pre-emergence followed by fenoxaprop-p-ethyl 50 g/ha + ethoxysulfuron 15g/ha 20 DAS (T4). Similar result was observed in terms of straw and biological yield with 137.38 and 152.37 %, respectively increase over control. In case of
straw yield (50.68 kg/ha) T5 was at par with T4 (46.65 kg/ha) and T6 (44.85 kg/ha). Weed management treatment did not significantly affect harvest index of direct seeded kharif rice.
The lower weed index was recorded in pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS (T5) (5.84 %) followed by pretilachlor 750g/ha pre-emergence followed by fenoxaprop-p-ethyl 50 g/ha + ethoxysulfuron 15g/ha 20 DAS (T4) (13.30 %) and pretilachlor 750g/ha pre-emergence followed by penoxsulam 30 g/ha + bentazone 1080 g/ha 20 DAS (T6) (17.49%). No significant change in N, P and K content was recorded in grain and stover whereas N, P and K uptake by the crop was significantly higher in pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS (T5). The mentioned treatment decreased N, P and K content in weeds and their uptake as compared to weedy check by 5.18, 22.08 and 6.78, and 50.18, 59.02 and 50.76 %, respectively over weedy check. The same treatment recorded higher available N, P2O5 and K2O by 7.55, 19.57 and 3.96 %, respectively over weedy check. Weed management treatment did not significantly affect soil organic carbon of direct seeded kharif rice.
The highest gross and net returns (103541 and 62751 ₹ /ha, respectively) were noted by pretilachlor 750g/ha pre-emergence followed by triafamone + ethoxysulfuron 60g/ha 20 DAS (T5) along with the highest B-C ratio (1.54) closely followed by pretilachlor 750g/ha pre-emergence followed by fenoxaprop-p-ethyl 50 g/ha + ethoxysulfuron 15g/ha 20 DAS (T4) (1.36).