POPULATION DYNAMICS AND MANAGEMENT OF WEEDS FOR ENHANCING PRODUCTIVITY UNDER DIRECT-SOWN RICE-BLACKGRAM-RICE CROPPING SYSTEM
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Date
2019
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Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.)
Abstract
“The field experiments were conducted during” kharif, “rabi” and summer “seasons of” 2016-17 and 2017-18 at Institute Research Farm, ICAR-National Rice Research Institute, Cuttack, Odisha. In kharif season dry-DSR, “the experiment was laid-out in randomized block design with three replications.”The treatment “consisted of ten weed management practices” viz.,”WW1: “Mechanical weeding” twice “at 20 and 40 days after” emergence (DAE) at 25 cm row spacing, WW2: “Pendimethalin 750 “g ha-1” (PE) “fb Bispyribac sodium” “25 g ha-1 (PoE) at”” 25 DAE at 25 cm row spacing, WW3: Pendimethalin 750 g ha-1 (PE) fb Mechanical weeding at 30 DAE at 25 cm row spacing, WW4: “Bispyribac sodium 30 g ha-1 at” 10 DAE fb Mechanical weeding at 30 DAE at 25 cm row spacing, WW5: One manual weeding at 30 DAE at 25 cm row spacing, WW6: One manual weeding at 30 DAE at 20 cm row spacing, WW7: Weed free (15, 30, 45 & 60 DAE) at 25 cm row spacing, WW8: Weed free (15, 30, 45 & 60 DAE) at 20 cm row spacing, WW9: Weedy plot at 25 cm row spacing and WW10: Weedy plot at 20 cm row spacing.
In rabi season, blackgram crop was grown in the same set of layout after the splitting of each 10 plot in two equal parts with design of split plot to study the residual “effect of weed management in” dry-DSR and rice straw mulch. The rabi blackgram crop, main-plot consisted of ten treatment of residual of weed management in dry-DSR viz., RWW1: “Mechanical weeding twice at 20 and 40 days after” emergence (DAE) at 25 cm row spacing, RWW2: “Pendimethalin 750 g ha-1 (PE) fb Bispyribac sodium 25 g ha-1 (PoE)” at 25 DAE at 25 cm row spacing, RWW3: Pendimethalin 750 g ha-1 (PE) fb Mechanical weeding at 30 DAE at 25 cm row spacing, RWW4: “Bispyribac sodium 30 g ha-1 at” 10 DAE fb Mechanical weeding at 30 DAE at 25 cm row spacing, RWW5: One manual weeding at 30 DAE at 25 cm row spacing, RWW6: One manual weeding at 30 DAE at 20 cm row spacing, RWW7: Weed free (15, 30, 45 & 60 DAE) at 25 cm row spacing, RWW8: Weed free (15, 30, 45 & 60 DAE) at 20 cm row spacing, RWW9: Weedy “plot at 25 cm row spacing and” RWW10: Weedy “plot at 20 cm row spacing and” sub plot consisted of two treatment of rice straw mulch viz., M1- rice straw mulch @ 4 t ha-1 and M2 - no mulch.
In summer season wet-DSR, crop were grown in the same set of layout and replication following in preceding crop to study the weed management practices and residual of rice straw mulch applied in rabi blackgram. The main-plot consisted of 10 weed management practices viz., DW1: “Mechanical weeding twice at 20 and 40 days after” sowing (DAS) at 25 cm row spacing, DW2: “Pendimethalin 750 g ha-1 (PE) fb Bispyribac sodium 25 g ha-1 (PoE) at 25 DAS” at 25 cm row spacing, DW3: Pendimethalin 750 g ha-1 (PE) fb Mechanical weeding at 30 DAS at 25 cm row spacing, DW4: “Bispyribac sodium 30 g ha-1 at 10 DAS fb Mechanical weeding” at 30 DAS at 25 cm row spacing, DW5: One manual weeding at 30 DAS at 25 cm row spacing, DW6: One manual weeding at 30 DAS at 20 cm row spacing, DW7: Weed free (15, 30, 45 & 60 DAS) at 25 cm row spacing, DW8: Weed free (15, 30, 45 & 60 DAS) at 20 cm row spacing, DW9: “Weedy plot at 25 cm row spacing and DW10: Weedy plot at 20 cm row spacing” and sub plot consisted of two treatment of residual of rice straw mulch applied in rabi blackgram viz., RM1- residual of rice straw mulch @ 4 t ha-1 and RM2 - residual of no mulch.
The results revealed that in kharif season dry–DSR, among the weed management treatments, weed free condition at 20 cm row spacing (WW8) gave “significantly higher growth parameters, yield” contributing characters, grain yield, straw yield, nutrient uptake by crop and weed control efficiency as well as significantly lower weed density, weed dry weight, weed index and nutrient removal by weeds at 60 DAE than others, “but it was at par with weed free check at 25 cm” row spacing (WW7), however these parameters, under treatment early post emergence application of bispyribac sodium 20 g ha-1 (at 10 DAE) fb mechanical weeding (at 30 DAE) at 25 cm row spacing (WW4); were found comparable with weed free treatment (WW7) “during both the years and on mean basis. The maximum net return and B:C ratio” were received under treatment early “post emergence application of bispyribac sodium 30 g ha-1” (at 10 DAE) fb mechanical weeding (at 30 DAE) at 25 cm row spacing (WW4); “which was at par with sequential application of pre-emergence pendimethalin 750 g ha-1 fb post-emergence bispyribac sodium 25 g ha-1” (at 25 DAE) at 25 cm row spacing (WW2), further B:C ratio under treatment pre-emergence pendimethalin 750 g ha-1 fb mechanical weeding (at 30 DAE) at 25 cm row spacing (WW3) “was also found comparable during both the years and on mean basis.”
In rabi season blackgram, different treatment of residual of weed management in dry-DSR did not have significant impact on growth parameters, yield attributing characters, harvest index, seed and stover yields and nutrient uptake by crop, “weed density, weed dry weight and nutrient removal by weeds at 60 DAS, available N, P and K content in soil” and enzyme activities (FDA, DHA and β-glucosidase) in rhizosphere soil, gross return, net return and B:C ratio. However, maximum values of crop related and minimum values of weed related parameters were recorded under residual of weed free condition at 20 cm row spacing (RWW8) and minimum was noted under residual of weedy check at 25 cm row “spacing (RWW9) during both the years and on mean basis.”
“As regards to” effect of “rice straw” mulch applied in rabi blackgram, significantly higher growth parameters, yield attributing characters, harvest index, seed and stover yields and nutrient uptake by crop, available K content and soil enzyme activities (FDA, DHA and β-glucosidase) in soil, gross return and net “return; whereas, significantly lower weed density, weed dry weight, nutrient removal by weeds at 60 DAS were noted under the treatment M1- rice straw mulch (4 t ha-1) “as compared to” M2-no mulch “during both the years and on mean basis.””
In summer season wet-DSR, treatment weed free condition at 20 cm row “spacing (DW8) gave significantly higher growth parameters, yield contributing characters, grain yield, straw yield, nutrient uptake by crop and weed control efficiency as well as significantly lower weed density, weed dry weight, nutrient removal by weeds at 60 DAS than others, but it was at par with weed free check at” 25 cm row spacing (DW7). Further, these parameters under treatment early post emergence application of bispyribac sodium 20 g ha-1 (10 DAS) fb mechanical weeding (30 DAS) at 25-cm row spacing (DW4) were found comparable with weed free treatment (DW7) “during both the years and on mean basis. The maximum net return and B:C ratio” were received under treatment early “post emergence application of bispyribac sodium 30 g ha-1 (10 DAS) fb mechanical “weeding (30 DAS) at 25 cm row spacing (DW4); “which was at par with sequential application of pre-emergence pendimethalin 750 g ha-1 fb post emergence bispyribac sodium 25 g ha-1” (25 DAS) at 25 cm row spacing (DW2). Further, in case of B:C ratio, treatment pre-emergence application of pendimethalin 750 g ha-1 fb mechanical weeding (30 DAS) at 25 cm row spacing (DW3) was also found comparable “during both the years and on mean basis.””
“Different treatments of” residual of “rice straw” mulch applied in rabi blackgram, failed to show significant effect “on growth” parameters, “yield contributing” characters, “grain yield, straw yield” and “nutrient uptake” by summer wet-DSR as well as “density and dry weight of weeds and nutrient” removal by weeds at 60 DAS. Similarly; gross return, net return and B:C ratio of summer wet-DSR also remained unaffected “during both the years and on mean basis.”
As regards to the system analysis of rice-blackgram-rice cropping system, the “rice equivalent yield and system productivity” were higher under the treatment combinations of WW8 (weed free check at 20 cm row spacing in kharif season dry-DSR)-RWW8M1 (residual of weed free at 20 cm row spacing with mulching of rice straw mulch in succeeding blackgram in rabi season)-DW8RM1 (weed free check at 20 cm row spacing in summer season wet–DSR with residual of rice straw mulch applied in rabi blackgram). Whereas, higher net income of the system and “available N, P and K status in soil” were registered under treatment combination of “WW4 (early post emergence application of bispyribac sodium 30 g ha-1”(10 DAE) fb mechanical weeding (30 DAE) at 25 cm row spacing in kharif dry-DSR)-RWW4M1 (residual of “early post-emergence application of bispyribac sodium 30 g ha-1”(10 DAE) fb mechanical weeding (30 DAE) at 25 cm row spacing with mulching of rice straw mulch in succeeding blackgram in rabi season)-DW4RM1 (early “post-emergence application of bispyribac sodium 30 g ha-1”(10 DAS) fb mechanical weeding (30 DAS) at 25 cm row spacing in summer wet–DSR with residual of rice straw mulch applied in rabi blackgram).
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